Metro’s Kate Model: 25,000 phantom cars a day on the I-5 bridge

How can we trust Metro’s model to predict the future, when it can’t even match the present?

Metro’s Kate travel demand model, used to plan the $7.5 billion Interstate Bridge, includes 25,000 phantom cars per day in its base year estimates.

The existing I-5 bridges over the Columbia River carried 138,800 vehicles on an average weekday in 2019, according to ODOT’s official traffic count data.

But not according to Metro’s Kate traffic model:  Kate claims the I-5 bridges carried 164,050 vehicles  in 2019

The difference shows Metro’s model isn’t accurate:  It can’t even replicate current conditions

And yet we’re expected to believe this same model can accurately predict traffic levels decades into the future?

This exaggeration is key to false claims about the severity of current and likely future traffic conditions, and is an illegal basis for the project’s federally required environmental analysis.

Metro’s Kate travel demand model claims 164,050 weekday vehicles in 2019

We obtained the outputs from the Metro travel demand model provided to the Interstate Bridge Project via a public records request.  The following portion of the Excel spreadsheet shows the vehicle counts for the I-5 bridge according to the Metro model.  This panel is from cells A1_B11 and cells F1:G11 in tab “summary” of a spreadsheet called “I5_xing_auto_truck_vol_comp_042922.xlsx” dated April 29, 2022.  (The same data appears in February, 2023 versions of the output of the Metro model).

 

The abbreviations for vehicle type are single occupancy, multiple occupancy and heavy and medium trucks; the abbreviations for direction are Northbound and Southbound.  These columns refer to the estimated 2019 No-Build (NB) forecast.  The total volume of vehicles sums to 164,050.

ODOT’s Traffic Counter shows only 138,780 vehicles per day.

The Oregon Department of Transportation maintains a series of automatic traffic data recorders that count the number of vehicles that use state highways.  Recorder number 26-004 measures traffic on the Interstate Bridge.  The following table, taken from the ODOT website, shows the average weekday traffic for each month in 2019.  The annual average (sum of monthly average traffic divided by twelve months) is 138,780 vehicles per day.

The difference:  more than 25,000 phantom cars per day.

Metro’s travel demand model claims the I-5 bridges are carrying 25,000 more vehicles per day than ODOT is actually counting.  This is a huge error:  Metro’s model over-states traffic volumes in the current year by more than 18 percent.

In essence, the EIS, which is supposed to be based on fact, is full of false claims about actual traffic levels on I-5.  This is a plain violation of the National Environmental Policy Act, which requires that data be accurate and scientifically sound (40 CFR § 1502.23).

IBR traffic modeling violates professional standards and federal rules

Traffic modeling is guided by a series of professional and administrative guidelines.  In the case of the proposed $7.5 Interstate Bridge Replacement Project, IBR and Metro modelers did not follow or violated these guidelines in many ways as they prepared their traffic demand modeling.  IBR modelers:

  • Didn’t assess accuracy of their previous modeling
  • Failed to calibrate their models to observed traffic levels
  • Failed to accurately account for capacity constraints
  • Ignored other models and more accurate data that contradicted their conclusions
  • Failed to exhibit scientific integrity
  • Failed to document their data and methods
  • Failed to commission an independent review of their analysis

Each of these errors constitutes a violation of professional standards for traffic forecasting, and invalidates the claims made the the IBR Draft Supplemental Environmental Impact Statement.

The Interstate Bridge Replacement (IBR) project’s traffic modeling efforts represent a significant departure from professional standards and federal guidelines, raising serious questions about the reliability of its projections and the integrity of its environmental review process. Sponsoring agencies are generally given substantial deference in their technical analyses, but such deference is completely unwarranted when the agencies systematically disregard or violate professional standards.

Google Gemini

A detailed examination of the project’s modeling work reveals systematic failures to follow established professional practices, federal directives, and state guidelines.

Ignoring errors in previous forecasts

Perhaps most troubling is the project team’s failure to examine the accuracy of their previous forecasting efforts. Federal Highway Administration (FHWA) guidelines explicitly direct agencies to:

“. . . critically review past efforts to be aware of the prior work and to improve on or complement that work” before undertaking new projections.

FHWA,  Interim Guidance On The Application Of Travel AndLand Use Forecasting In NEPA, 2010, page 6. 

The National Academy of Sciences specifically recommends that agencies periodically report forecast accuracy, noting that such reporting “reveals any bias in the traffic forecasts” and “provides the empirical information necessary to estimate the uncertainty surrounding their traffic forecasts.” (National Academies of Sciences, Engineering, and Medicine. 2020. Traffic Forecasting Accuracy Assessment Research. page S-10).

IBR officials utterly failed to look at their prior modeling efforts and acknowledge or learn anything from their earlier failures.  The evidence is stark: While the CRC modeling predicted 1.5 percent annual traffic growth in vehicle traffic on the I-5 bridges between 2005 and 2030, actual growth  was just 0.3 percent annually through 2019, and 0.1 percent per year from 2005 through 2023.

Despite this significant disparity, the latest iterations of Metro and IBR models inexplicably predict that traffic growth will more than double to 0.63-0.79 percent annually through 2045 in the “No-Build” scenario. This represents a fundamental failure to learn from past mistakes and adjust methodologies accordingly as demanded by FHWA and NAS standards.

Metro and IBR models simply failed to look at whether their previous models were accurate; instead choosing to hide these forecast misses from the public.  The SDEIS fails to report that the forecasts that were contained in the 2008 Environmental Impact Statement have proven to be wrong by a factor of four.  This failure is a fundamental violation of professional standards.

Failure to calibrate the model to actual conditions

The modeling effort suffers from serious calibration issues. FHWA guidance emphasizes that traffic models must be accurately calibrated to real world values for use in NEPA analyses

In the context of a NEPA study, it is important for the study team to focus any calibration and validation efforts that they undertake on the study area. Typically, a regional travel demand model will have been adequately calibrated and validated at least at a regional level prior to adoption. While it is important for the study team to critically review the documentation of this effort, it is suggested that more emphasis be placed on checks at the study area level. It is suggested that the study team scale their calibration and validation effort according to the scale of the analysis, such as its geographic scope.

Calibration A meaningful calibration effort would include: . . .

  • Comparison of modeled traffic volumes with traffic counts both for individual roadway segments and at more aggregate levels such as throughout the study area

Federal Highway Administration, Interim Guidance On The Application Of Travel And Land Use Forecasting In NEPA, March 2010, page 10 (emphasis added)

Metro’s own validation report reveals that their model overestimates daily traffic volumes on I-5 by tens of thousands of vehicles per day, and over estimates PM peak hour northbound traffic at the I-5 Bridge by 18 percent. This overestimation leads to exaggerated predictions of congestion and potentially misrepresents both the project’s benefits and environmental impacts.  These calibration errors are not disclosed the the DSEIS.

Not constraining “No-Build” forecasts to reflect highway capacity

Both Metro and IBR models predict physically impossible traffic flows, violating FHWA guidance on realistic capacity constraints. The FHWA Traffic Analysis Toolbox specifically warns that “care must be taken to ensure that forecasts are a reasonable estimate of the actual amount of traffic that can arrive within the analytical period.”  Federal guidance makes it clear that this is critical to the accuracy of the modeling.

While the I-5 bridges’ northbound capacity is approximately 5,000 vehicles per hour, the models estimate peak hour flows of 5,740 to 6,290 vehicles – 16 to 25 percent above capacity. These predictions continue to rise in the No-Build scenario, reaching 6,375 (Metro) and 6,905 (IBR) vehicles by 2045.  The IBR Traffic Technical Report fails to acknowledge that its estimates of peak hour traffic flows exceed the physical capacity of the roadway, in plain violation of federal guidance.

Deficient documentation and lack of transparency

The project’s modeling process operates as a “black box,” contradicting established professional standards. As NCHRP Report #765 emphasizes:  “Providing transparency in methods, computations, and results is essential.”

IBR and Metro have effectively concealed many of the details and limitations of their traffic forecasts.  Professional standards impose an affirmative responsibility on modelers to fully disclose this information.  Metro and IBR generally refused to provide detailed information about their traffic modeling, except when compelled to do so under public records laws.  Metro does not publish on its website the calibration report for its travel demand model, which shows that the model systematically over-states I-5 traffic levels.  As noted above, Metro and IBR models failed to disclose the errors in their earlier forecasts.

Providing transparency in methods, computations, and results is essential. . . . The analyst should document the key assumptions that underlie a forecast and conduct validation tests, sensitivity tests, and scenario tests—making sure that the results of those tests are available to anyone who wants to know more about potential errors in the forecasts.

National Cooperative Highway Research Project Report, “Analytical Travel Forecasting Approaches for Project-Level Planning and Design,” NCHRP Report #765

Federal regulations (40 CFR § 1502.23) explicitly require “scientific integrity” in environmental documents, mandating that agencies “shall identify any methodologies used and shall make explicit reference to the scientific and other sources relied upon for conclusions in the statement.”

Ignoring and omitting better models and more accurate data

Perhaps most egregiously, the IBR project has completely disregarded more precise modeling work it already paid for. In 2013, the states spent over $1.5 million commissioning CDM Smith to prepare a detailed “Level 3” traffic model for the Columbia River Crossing. This model achieved less than 1 percent variance with actual traffic levels – far better than Metro’s current 18 percent overestimation. In 2023, spent nearly $800,000 to have traffic modeler Stantec estimate traffic levels for the I-5 bridges.   The Stantec model was calibrated with about 2.5 percent variance from actual traffic levels.  Yet the IBR team has made no mention of these more accurate modeling efforts in the Supplemental Draft Environmental Impact Statement.

Not obtaining independent review

The U.S. Department of Transportation’s guidance is unequivocal about the need for independent review: “A senior-level peer review, internal and/or external, is therefore necessary… An external peer review by an independent third party can greatly improve its credibility with potential investors, lenders, government officials with oversight and approval responsibilities, and others.” Yet neither Metro nor IBR commissioned such a review.

Not verifying value of time assumptions

The IBR will be a tolled facility; accurately forecasting traffic levels on tolled roads and bridges depends directly on accurately estimating the value that travelers attached to time savings on tolled routes.  Guidance from the Federal Highway Administration directs states to document the reasonableness and reliability of their value of time estimates. (Federal Highway Administration, Interim Guidance On The Application Of Travel And Land Use Forecasting In NEPA, March 2010,  page 13).

Both the Metro “Kate” travel demand model and the Stantec Level 2 traffic and revenue study purport to predict traveler reactions to varying toll levels, but rely on questionable and largely un-documented assumptions about travelers’ value of time. Stantec’s own report acknowledges the speculative nature of their work, stating that “in many instances, a broad range of alternative assumptions could be considered reasonable… and any changes in the assumptions used could result in material differences in estimated outcomes.” Stantec explicitly disclaims liability for their assumptions, noting that “by their very nature, assumptions regarding information or data are accepted as true or certain to happen without actual proof of same.”  Because these value of time assumptions are undocumented, it is likely that the travel demand model substantially mis-estimates actual traffic patterns, invalidating the project’s claims about environmental impacts.

Implications

These systematic failures in traffic modeling raise fundamental questions about the Interstate Bridge Replacement project’s planning process and environmental review. The consistent pattern of overestimating traffic growth, ignoring capacity constraints, and failing to document key assumptions suggests that the project’s justification rests on questionable analytical foundations.

The project’s refusal to acknowledge past forecasting errors, examine more accurate existing models, or subject their work to independent review indicates a troubling lack of scientific rigor. These shortcomings not only violate federal guidelines and professional standards but also potentially mislead decision-makers and the public about the project’s necessity and impacts.

As the project moves forward, these modeling deficiencies must be addressed. At minimum, the SDEIS should incorporate the more accurate Level 2 and Level 3 modeling (like that done by CDM Smith and Stantec), properly document assumptions and methods, and submit their work for independent peer review. Without these basic steps, the project’s traffic projections – and the broader environmental review process that depends on them – lack the scientific integrity required by federal law.

Cooking the Books: How IBR used “Post-Processing” to alter the Metro Model

To hear project officials tell it, traffic projections emerge from the immaculate and objective Metro “Kate” traffic model

But in reality, IBR traffic projections are not the outputs of the Kate travel demand model.  Instead, IBR consultants have altered the Metro numbers, something the label “post-processing.”

But what they’ve done, doesn’t meet the professional standards for post-processing—they cooked the books.

Post-processing of Kate’s estimates isn’t needed because Kate produces detailed, daily and hourly estimates for the I-5 bridges

IBR made contradictory, and unexplained adjustments to Kate predictions: moving thousands of daily vehicles from I-5 to I-205, and hundreds of peak hour vehicles from I-205 to I-5.

IBR consultants failed to follow the accepted and required practice of fully documenting their so-called “post-processing” calculations

IBR traffic estimates can’t be replicated using the post-processing steps described in the DSEIS

The Interstate Bridge Replacement project has been caught fudging its traffic numbers. While IBR officials repeatedly claimed their traffic forecasts came directly from Metro’s supposedly authoritative regional travel model, internal documents reveal IBR consultants secretly altered these numbers without proper documentation or justification.

Through public records requests, we’ve learned that IBR staff made substantial undocumented changes to Metro’s model outputs, which they misleadingly labeled as “post-processing.” These alterations further inflated already questionable peak-hour traffic projections for I-5 and present a distorted picture of the project and its environmental impacts.

The myth of the Metro model

In planning circles, people regularly genuflect to the supposedly infallible Metro “Kate” travel demand model, representing it as an independent and objective source of precise travel information.  IBR officials, including project director Greg Johnson, repeatedly assured the public and elected leaders that their numbers came straight from Metro’s modeling. Johnson testified to Metro Council in January 2022 that “What sizes the bridge is the data that we take from the regional models that are a part of Metro and RTC.” RTC Director Matt Ransom went further, claiming the modelers were “walled off” from policy people to ensure objectivity.

IBR consultants altered the outputs of the Metro Model

These claims were false. IBR didn’t use Metro’s model outputs – they changed them.

The alterations were substantial. For 2045 “No Build” forecasts, IBR moved about 15,000 daily trips from I-5 to I-205 compared to Metro’s model. But then for their preferred alternative, they shifted 10,000 trips in the opposite direction – from I-205 back to I-5. They provided no explanation for these contradictory adjustments.

Here are the receipts.  First, the output from the Metro model, taken from a Metro spreadsheet, obtained via public records requests:  This is the February 27, 2023 version; rows showing vehicle class, travel direction and columsns showing hourly volumes are suppressed.  Values shown are average weekday traffic in both directions for the No Build (“NB”) and Locally Preferred Alternative (“SDEIS”).  Metro’s model outputs are substantially similar or identical for early model runs, such as a spreadsheet dated April 29, 2022, which also says, for example, that the daily No-Build volume would be 190,841.

And here are the IBR’s “post-processed” data.  The first post-processed data was released in response to a public records request of IBR in July, 2022.

The IBR project used its “post-processing” to dramatically shift the picture painted by the Metro travel demand model:  In the 2045 No-Build scenario, it moved nearly 15,000 vehicles from I-5 to I-205, changing predicted traffic on I-5 from 190,841 (Metro model) to 176,000 (IBR, post-processed), and changing I-205 traffic from 200,129 (Metro Model) to 215,000 (IBR post-processed).  Conversely, “post-processing” shifted trips in the “build” or Locally preferred alternative, from I-205 to I-5.  These huge adjustments aren’t fully explained; it is clearly a strong indictment of the inaccuracy of the Metro Model if its predictions are off by such a large amount.  In addition, if the model results need to be altered so substantially, then the process, method and calculations used to make those changes need to be more fully documented and explained.

 

Inflated Peak Hour Estimates

Even more troubling, IBR inflated peak hour traffic estimates above Metro’s already high projections. For northbound PM peak traffic in 2045, IBR boosted Metro’s forecast by 8-15%. Their “post-processed” estimate of 6,905 vehicles per hour is 530 vehicles higher than Metro’s model output of 6,375.  As we’ve noted before, the failure to constrain traffic predictions to the actual peak hour capacity of the I-5 bridges (fewer than 5,000 vehicles per hour in the afternoon peak) produces highly inaccurate forecasts.

This isn’t legitimate “post-processing.” In transportation planning, post-processing typically means making technical adjustments when a model only provides daily totals or corridor-level data. But Metro’s model already generates hourly volumes specifically for the I-5 bridge. No such adjustments were needed.

To be sure, there are serious problems with Metro’s Kate model.  As we’ve pointed out, it systematically overstates traffic levels on I-5, and predicts traffic that exceeds the freeway’s capacity at peak hours.  Part of the reason that IBR is altered Kate’s outputs is that they too recognize that Kate overstates I-5 traffic levels.  What IBR is really saying is something no one in the region will acknowledge:  the Kate model is wildly inaccurate, especially when it comes to predicting traffic for this $7.5 billion dollar project.

IBR failed to follow basic professional standards in documenting these changes. Oregon DOT’s Analysis Procedures Manual requires detailed documentation of all assumptions, factors and calculations used in traffic forecasting. (See Appendix I below for details).  IBR provided only a vague one-paragraph description of their methodology in response to public records requests. They failed to produce the required spreadsheets showing their work.

When we attempt to replicate IBR’s stated methodology, their numbers don’t add up. They claimed to calculate growth rates from Metro’s model and apply them to 2019 base year traffic. But their final outputs don’t match what this process would produce. Their “post-processed” 2045 No Build estimate of 176,000 daily vehicles is over 7,000 higher than their own methodology would generate.

IBR made conflicting adjustments in “post-processing.”

IBR’s adjustments completely change the story about how their preferred alternative would affect traffic patterns. Metro’s model shows building the project (moving from the No-Build to the Locally Preferred Alternative) would significantly reduce I-5 traffic (-14 percent) while increasing I-205 traffic (+9 percent). But IBR’s altered numbers claim minimal changes: just a 1 percent reduction on I-5 and a 4% decrease on I-205.

Other models of I-5 traffic required no post-processing

What makes these alterations particularly suspicious is that IBR only claimed to have “post-processed” their numbers after being challenged to reveal their methodology through public records requests. Neither the CDM Smith Investment Grade Analysis nor the Stantec Level 2 study – both based on Metro’s model – mention any “post-processing” adjustments.  And calibration reports show that both the CDM Smith and Stantec Level 2 models have a much better “fit” with existing traffic levels than the Metro model.

“Post-processing” is an industry-wide euphemism for altering model results highway agencies don’t like

Unfortunately, “post-processing” is a widespread practice among highway planners across the nation.  A study undertaken by Transportation for America, discussed in the article that Ben Ross and I wrote for Dissent—Highway Robbery—found

. . . modelers from seven states told the advocacy group Transportation for America that their organizations alter outputs manually based on “engineering judgment” or “long-range trends” as part of their post-processing. Similar reports come from former employees of highway agencies elsewhere.

The pattern is clear: IBR officials misled the public by claiming their numbers came directly from Metro’s  model, while secretly altering those numbers without proper documentation or justification. These undisclosed changes conveniently support their preferred narrative about traffic patterns and project needs.

This revelation raises serious questions about the integrity of IBR’s entire analysis process. How can the public trust any of their claims when they’ve been caught manipulating fundamental traffic data while hiding those manipulations from oversight?

It’s time for IBR to come clean. They need to:

  1. Release complete documentation of all changes made to Metro’s model outputs
  2. Provide detailed justification for each adjustment
  3. Submit their methodology for independent peer review

Until then, neither the public nor decision makers should trust IBR’s traffic projections. The project’s basic premise – that we need a massive expansion to handle future traffic – rests on numbers that appear to have been manipulated to support a predetermined conclusion.

False claims about post-processing in the Draft Supplemental Environmental Impact Statement (SDEIS).

The SDEIS offers this explanation of its “post-processing”:

Post-processing is not the substitution of judgment or guesses for the results of a transportation model. Rather, it is a comprehensive, systematic approach to account for the fact that the results of a regional travel demand model may be highly accurate on an aggregated regional basis (e.g., screenlines), but may not be accurate for individual roadways, ramps, or intersections within the modeled region . .
DSEIS, Transportation Technical Report, page 4-12

Actually, this isn’t the definition of post-processing in NCHRP 765.  Post-processing refers to adapting a models output for a geography (road section) or time period (for example, hourly, rather than daily) for which the underlying model does not provide estimates.  In the case of Metro’s RTDM, it directly does provide estimates:  the Interstate Bridge is one of the identified screenlines in the Metro model, and the model provides both daily and peak hour volumes.

Critically, while the SDEIS claims that it followed “industry standard” practices, and used the guidance of NCHRP 765, and while it outlines in three vague bullet points (pages 20-21 of the Transportation Methods Report), it fails to show how it got from the values taken from the Metro Regional Travel Demand Model to the “post-processed results” it included in the SDEIS.  This is a clear violation of professional practice, federal guidance and Oregon’s Analysis Procedures Manual, all of which require that analysts document their calculations whenever they perform “post-processing.”  As noted above:  Following the steps IBR described, we were unable to duplicate their estimated values, and their post-processing produced contradictory changes in daily and peak hour travel adjustments.

In this case, IBR isn’t using post-processing for its stated purpose (filling in geographic or temporal gaps in RTDM predictions) but rather for revising and dramatically changing the outputs of the RTDM.  IBR is effectively admitting that the Metro Kate RTDM is poorly calibrated and inaccurate, and is trying to “fix” these problems with post-processing.

Appendix A:  Required Documentation for Post-Processing

Both the “industry standard” manual for “post-processing” (NCHRP 765) and ODOT’s own Analysis Procedures Manual require a clear documentation of all of the data, assumptions and calculations used in post-processing.  IBR violates both of these manuals by failing to document how it “post-processed” traffic data.

NCHRP 765

It is critical that the analyst maintain personal integrity. Integrity can be maintained by working closely with management and colleagues to provide a truthful forecast, including a frank discussion of the forecast’s limitations. Providing transparency in methods, computations, and results is essential. . . . The analyst should document the key assumptions that underlie a forecast and conduct validation tests, sensitivity tests, and scenario tests—making sure that the results of those tests are available to anyone who wants to know more about potential errors in the forecasts.

National Cooperative Highway Research Project Report, “Analytical Travel Forecasting Approaches for Project-Level Planning and Design,” NCHRP Report #765 (Emphasis added)

ODOT Analysis Procedures Manual

6.2.3 Documentation

It is critical that after every step in the DHV [design hour volume] process that all of the assumptions and factors are carefully documented, preferably on the graphical figures themselves. While the existing year volume development is relatively similar across types of studies, the future year volume development can go in a number of different directions with varying amounts of documentation needed. Growth factors, trip generation, land use changes are some of the items that need to be documented. If all is documented then anyone can easily review the work or pick up on it quickly without questioning what the assumptions were. The documentation figures will eventually end up in the final report or in the technical appendix.

The volume documentation should include:

  • Figures/spreadsheets showing starting volumes (30 HV)
  • Figures/spreadsheets showing growth factors, cumulative analysis factors, or

travel demand model post-processing.

  • Figures/spreadsheets showing unbalanced DHV
  • Figure(s) showing balanced future year DHV. See Exhibit 6-1
  • Notes on how future volumes were developed:

If historic trends were used, cite the source.

If the cumulative method was used, include a land use map, information that documents trip generation, distribution, assignment, in-process trips, and through movement (or background) growth.

If a travel demand model was used, post-processing methods should be specified, model scenario assumptions described, and the base and future year model runs should be attached

ODOT, Analysis Procedures Manual, (Emphasis added) https://www.oregon.gov/odot/Planning/Pages/APM.aspx

Appendix B:  Altered Post-Processed Estimates in the SDEIS

The SDEIS as published contains further altered estimates of “No-Build” travel levels.  In 2022 and 2023, IBR documents claimed that the “No-Build” traffic level on the I-5 bridges in 2045 would be 176,000 vehicles per average weekday, according to their “post-processed” estimates.  As noted, the Metro model continued to estimate I-5 bridge traffic in the No-Build condition in 2045 at 190,841 vehicles per average weekday.  In the published version of the SDEIS, IBR has, without explanation, changed the No-Build traffic estimate to 180,000 vehicles per average weekday.  Meanwhile, the traffic estimates for I-5 in the Locally Preferred Alternative (175,000 vehicles per average weekday are unchanged.  As noted above, IBR does not document its post-processing calculations, and provides no explanation for the shift in estimated No Build traffic from 176,000 vehicles per day to 180,000 vehicles per day.

Inventing millions of phantom trucks to sell a wider bridge

The $7.5 billion plan to widen the I-5 bridges across the Columbia River is being sold, in part, based on claims that it will be used by millions of phantom trucks.  

Metro’s biased truck modeling over-states current I-5 truck traffic by almost 70 percent:  more than 2 million phantom trucks per year.  Metro’s model says more than 17,000 trucks crossed the I-5 bridges each day in 2019; ODOT’s traffic data shows fewer than 10,000 truck crossings.

Truck traffic on the I-5 bridges is going down, and has declined almost half since 2005

Previous truck growth predictions for the CRC proved to be wildly wrong; the project’s EIS predicted truck traffic would grow more than 2 percent per year between 2005 and 2030; instead, it has declined at an annual rate of nearly 5 percent.

The decline isn’t an anomaly:  statewide, Oregon truck freight volumes have declined 22 percent in the past 13 years, according to federal statistics

Metro’s truck traffic forecast isn’t based on a model:  It just appropriates a growth factor based on an unrealistic and inaccurate federal data series that US Department of Transportation officials concede is used for political purposes, not actual decision-making.

In the ongoing debate surrounding the Interstate Bridge Replacement (IBR) project, a critical issue : the severe overestimation of truck traffic on the I-5 bridge. This commentary examines the flaws in current modeling practices and their potential impact on project planning and decision-making.  IBR and Metro inflated truck counts to exaggerate the current importance of trucks, and built traffic models that grossly overestimate the growth in truck freight.  In essence, these flawed traffic models mean that IBR is widening a freeway to accommodate that truck traffic that doesn’t now exist, and based on false predictions of future truck traffic growth–when in reality truck traffic has been declining.

Millions of phantom trucks are being used to justify a multi-billion dollar freeway widening

Metro’s forecast that grossly overstates current truck traffic

The most basic test of a model’s accuracy is whether its predictions match actually observed current reality.  Metro’s traffic model—the basis for the IBR traffic estimates and environmental analysis—claims that 17,373 medium and large trucks (Class 4-13) crossed the I-5 bridge daily in 2019.  We obtained the Metro traffic forecast information via a public records request.  Here’s an excerpt of a spreadsheet showing estimated 2019 truck traffic crossing the I-5 bridges:

The figures for heavy and medium trucks in the northbound (nb) and southbound (sb) directions are highlighted.  Together, these estimates total 17,373 trucks (6,861 + 6,813 + 1,853 + 1,845) daily.

Actual traffic data show’s that’s simply not true:  Oregon Department of Transportation (ODOT) traffic count data (full data below) reports just 10,260 such trucks per day. This discrepancy amounts to a staggering overestimation of 69 percent – or 7,113 phantom trucks every day.  Metro’s model simply isn’t accurate.

This isn’t a minor statistical error. It means planning for the I-5 bridges is somehow designed to accommodate more than  than 2.6 million non-existent annual truck trips in the base year alone.  The wild exaggeration of the scale of truck traffic shows that the Metro travel demand modeling is deeply flawed, and biased to support the sales pitch for bridge expansion.  It’s hardly a reasonable basis for making a multi-billion dollar spending decision.

Historical trends vs. Metro predictions

Metro’s truck forecast doesn’t merely get current truck volumes wrong; it grossly misrepresents the historic trend.  Metro claims truck traffic is up:  Oregon Department of Transportation data show that truck traffic on the I-5 bridges has actually gone down.  Here’s the data, downloaded from ODOT’s own website.

– In 2005, ODOT reported 19,428 class 5-13 trucks crossing the I-5 bridge daily.
– By 2019, this number had decreased to 9,809 trucks per day.
– This represents an annual decline of almost 5 percent annually over 14 years.
– Just prior to the pandemic, truck traffic on the I-5 bridges was down almost half compared to 2005

In spite of the historic trend in declining truck travel, the estimates developed by Metro and IBR make the startling claim that in the future, truck travel will increase dramatically.  Metro predicts I-5 truck traffic will grow at 1.9 percent annually, projecting an increase from their (overestimated) 17,373 trucks in 2019 to 28,382 trucks in 2045 under the No Build scenario.

The Interstate Bridge Project has falsely portrayed truck traffic levels on the I-5 bridges as increasing.  In public presentations, the IBR has claimed that truck traffic increased from 11,000 vehicles per day in 2005 to 14,000 vehicles per day in 2019.  While that’s lower than the 17,373 trucks claimed in the Metro model, its still much higher than the number of trucks actually recorded by ODOT traffic counting.

IBR claims that I-5 bridge truck traffic rose by more than 25 percent between 2005 and 2019, when ODOT’s own traffic count data show that it declined by almost half over that same period.

Another forecast prepared by for IBR by Stantec, a so-called  Level 2 traffic study, specifically called out the error in the Metro travel demand model’s truck estimates:

As shown before in Table 2-3, the heavy trucks constitute approximately 6.5% of total traffic on the I-5 Interstate Bridge. The [Metro] RTDM estimates heavy trucks to be about 9% of the total bridge traffic. As such, adjustments were necessary to reallocate the estimated truck trips to the proposed tolling classifications to be consistent with observed truck shares. 

Stantec Level 2 Study, page 4-8

Stantec has a more realistic baseline—11,638 trucks per day in 2015—but calls for an even faster annual growth rate of  2.7 percent, to as many as 25,500 trucks in 2045.

A consistent pattern of exaggerating truck growth

Exaggerating the level and future growth of truck traffic is a long-standing tactic of the highway widening crowd.   The Environmental Impact Statement for the proposed  Columbia River Crossing (CRC) project—the IBR’s predecessor—using a previous version of Metro’s model, claimed that truck traffic would increase in a “No Build” scenario from 10,855 trucks per day in 2005 to 19,405 trucks per day in 2030 – an annual growth rate of 2.3 percent.

Reality has proven far different. Between 2005 and 2019, I-5 bridge truck traffic actually decreased at an annual rate of nearly 5 percent.

Freight forecasts have been proven wrong:  Truck freight is declining, not increasing

Truck traffic levels are projected using a completely different “module” than the rest of the Metro regional travel demand model.  The truck module is based on data which claims that truck traffic nationally (and locally) will increase steadily over time.  The data source for this claim is highly suspect.   Metro’s RTDM relies on the Federal Freight Analysis Framework 3 (FAF3), which is based on data from 2007 – now over 15 years out of date.  Essentially, Metro just creates a “growth factor” from the FAF data and applies it to its (over-estimated) level of current truck traffic.  Here’s an excerpt from Metro’s methodology explanation:

The FAF3 data essentially assumed steadily increasing tonnage flow of truck freight, and Metro essentially “copied and pasted” these growth factors into its model.  But the continuous and aggressive growth assumed in FAF 3 hasn’t occurred. More recent versions of this data series (FAF4 and FAF5) show much lower levels of truck freight activity and project slower growth.

  • The 2011 Oregon Freight Plan, based on FAF2 data, projected an increase in truck freight from 294 million tons in 2010 to 508 million tons in 2035 – a 73% increase over 25 years (2.2% annual growth).
  • In reality, FAF5 data shows truck freight volumes declined from 294 million tons in 2010 to 229 million tons in 2023 – a decrease of 22% over 13 years (-1.9% annually).

In short, forecasts of future trucking activity in Oregon based on the Freight Analysis Framework have proven to be monumentally wrong:  rather than increasing by more than 2 percent per year, statewide truck freight volumes have been declining at almost 2 percent per year.  This updated FAF5 data—not mentioned in the Metro report or the DSEIS—confirm the pattern shown in ODOT traffic counts:  truck traffic across the I-5 bridges is declining, not increasing. Yet the IBR is predicating on models that embrace outdated, and now completely discredited forecasts of ever-increasing truck volumes.

Freight Forecasts are a politically driven talking point, not real data

Not only that, but officials at the U.S. Department of Transportation concede that the truck forecasts in FAF are created for political purposes, and are not a valid basis for decision-making.  The DOT’s chief economist wrote:

Other federal modal administrations prepare forecasts, but it is done more out of curiosity, to provide talking points for their administrators’ speeches. The Federal Highway Administration’s Office of Freight Operations has for the last several years prepared the Freight Analysis Framework, which forecasts freight flows out 20 years – not just for trucking, but for all modes of freight transportation. But we don’t actually use the FAF forecasts for any real decision-making. The forecasts help to inform the political process in a general way, and provide ammunition for politicians who want to spend more on transportation infrastructure.

The truck freight forecasts in the Freight Analysis Framework–especially the now out-dated FAF3 and FAF4 estimates aren’t a legitimate or sound basis for making transportation investments.

The Port Traffic Myth

Another misconception this analysis dispels is the oft-repeated claim that Port activity significantly impacts I-5 truck traffic. A 2013 study commissioned by ODOT found that only about 50 trucks per day from the Port of Portland’s Terminal 6 use the I-5 bridge. This amounts to roughly one truck every 30 minutes – hardly the flood of port-related traffic often cited to justify the project’s urgency.

The Port of Vancouver averages about 330 truck trips total per day, with no clear data on how many actually cross the I-5 bridge.

Bad Truck Estimates Undermine the IBR

The consequences of these overestimations extend far beyond academic interest. Accurate truck traffic forecasts are crucial for several reasons:

1. Project Justification: Inflated truck traffic numbers may be used to overstate the need for capacity expansion.
2. Design Considerations: Overestimating truck volumes could lead to overbuilt infrastructure, wasting taxpayer money.
3. Toll Revenue Projections: Truck tolls are four times higher than those charged to cars, so getting the estimate to truck traffic right is essential to any financial analysis. As noted by transportation expert Robert Bain, unreliable truck forecasts can significantly impact projected toll revenues, potentially putting the financial viability of the project at risk.

The Need for Accountability and Transparency

Given the magnitude of the discrepancies identified, it’s crucial that Metro and other agencies involved in the IBR project address these issues openly. Oregon and Washington officials should:

1. Commission a thorough, independent review of the truck traffic modeling methodologies being used.
2. Understand why the models diverge so significantly from ODOT’s actual traffic count data.
3. Update forecasts using the most recent FAF5 data, with a critical examination of its applicability to real-world decision-making.
4. Right-size the project’s  design in light of more accurate truck traffic data.

Conclusion

The phantom trucks populating Metro’s models represent more than just a statistical anomaly. They embody a broader pattern of biased forecasting that has plagued major infrastructure projects for decades. As we contemplate spending billions on the Interstate Bridge Replacement, it’s imperative that we base our decisions on robust, reality-based data rather than inflated projections.

To summarize the key statistical discrepancies:
– Current traffic: Metro claims 17,373 trucks/day vs. ODOT’s 10,260 trucks/day (69% overestimation)
– Historical trend: 4-5% annual decline (2005-2019) vs. Metro’s projected 1.9% annual growth
– Long-term forecast: Metro projects 28,382 trucks/day by 2045, while the historical trend would suggest fewer than 7,000 trucks/day if continued

The citizens of Portland and Vancouver deserve infrastructure planning grounded in fact, not fiction. It’s time to exorcise these phantom trucks from our models and engage in a clear-eyed, data-driven discussion about the true needs of our regional transportation system.

ODOT’s I-5 Traffic Count Data, by Vehicle Class, 2005-2019

They’re digging in the wrong place

The Interstate Bridge Project proposes spending $7.5 billion to widen I-5, but misses the real bottleneck.

A new, independent analysis by national traffic expert Norm Marshall of Smart Mobility, Inc., shows that the proposed IBR project fails to fix the real bottlenecks affecting I-5 traffic.

Traffic problems on I-5 are caused by bottlenecks outside the project area, that aren’t affected by the IBR project.  

IBR will make traffic problems worse, especially in the morning peak hour, by funneling more traffic into these bottlenecks.

The limited 3 lanes of I-5 in each direction between the Fremont Bridge and Lombard will continue to cause daily congestion.

The Oregon and Washington highway departments are planning to widen the freeway to ten or more lanes on a stretch of I-5 between Portland and Vancouver, rebuilding seven intersections and five miles of highway.  The community group Just Crossing Alliance retained national traffic modeling expert Norm Marshall of Smart Mobility, Inc., to conduct a detailed review of the IBR’s traffic modeling.  But Marshall’s analysis shows this added capacity doesn’t address the real bottlenecks on I-5, which are actually further south of the actual project area.

Far from fixing the congestion problem, Marshall’s analysis shows that this will actually make traffic much worse, especially in the morning rush hour.  Essentially, the IBR project is building a large funnel to pour even more traffic into the morning southbound bottleneck at about North Lombard.  The I-5 freeway narrows to just three lanes between Lombard and the Fremont Bridge, and this is the area where traffic backs up today.  Adding even more capacity at and near the bridge simply funnels more cars, more quickly into this bottleneck–and will make traffic conditions even worse.

Marshall’s analysis, using detailed hourly traffic speed data for I-5, shows that traffic actually moves more rapidly across the Interstate Bridge than it does in the area south of the project in both the morning and afternoon peak hours.  In the morning, southbound traffic from Vancouver backs up from the Lombard Street exit.  These speed maps confirm what regular commuters already know:  the slow down doesn’t occur on the I-5 bridge—traffic moves at close to 40 miles per hour on the I-5 bridge and approaches.  The real slow down is right at Lombard Street, where traffic slows to less than 20 miles per hour.  (Between the purple triangles)

In the afternoon, Marshall’s analysis shows the real bottleneck is at about Victory Boulevard (which is near the southern boundary of the I-5 widening project).  Today, traffic accelerates once it gets past this bottleneck.  Again–it is the limited capacity of I-5 between Victory Boulevard and the Fremont Bridge, not the width of the I-5 Columbia River Bridges—that is the real bottleneck.  Again, these maps show what regular commuters already know, the big slowdowns on I-5 are well south of the I-5 bridge.  For several miles between the Fremont Bridge and Victory Boulevard, traffic moves at 11-13 miles per hour.  After Victory, traffic accelerates; and once one gets to the I-5 bridge, traffic steadily moves faster, and when exiting the bridge, traffic moves at 48 miles per hour—roughly the speed corresponding to maximum throughput.  As Marshall points out this is a classic example of what traffic engineers call “queue discharge”–traffic speeds increase once you get past the bottleneck.

In one of the most memorable scenes from Raiders of the Lost Arc, Indiana Jones and his partner Sallah decipher the instructions from a medallion that shows the location of the Arc of the Covenant, and in the process, see that the Nazi’s seeking the Arc have missed a vital piece of information, Jones and Sallah to exclaim “They’re digging in the wrong place.”  In simple terms, that’s exactly what the flawed traffic models generated by the IBR have done.  They’re pretending that the bottleneck limiting traffic flow on I-5 between Portland and Vancouver is the width of the I-5 bridge and its approaches.  But Marshall’s analysis shows that the real bottlenecks are further south—and won’t be resolved by the added capacity.

How can a sophisticated model get things so wrong?

Despite the trappings of technical expertise, there’s a very clear reason why the models used by the IBR project are wrong.  The models use something called “static traffic assignment” or STA, which break the freeway system into separate segments, and estimate the traffic flow on each segment separately and independently.  If the STA model predicts traffic that exceeds the capacity of a roadway one one segment, it fails to address how that has the inevitable upstream and downstream effects.  In the real world, if a road is jammed to capacity at one segment, traffic backs up onto preceding segments of roadway, and also no more than the maximum amount of traffic on a constrained segment can flow into the next segment.  As a result, even though the capacity of the I-5 bridges is no more than about 5,000 vehicles per hour in the afternoon peak direction, the IBR model claims that more than 6,200 vehicles per hour are crossing the bridge. The STA model assumes that traffic doesn’t back up into preceding segments when flows exceed capacity, and also assumes that more traffic flows into succeeding segments than is possible.

This kind of model assumption was necessary forty and more years ago when computer processing power made it hard to allow for these situations.  But today, traffic modelers have developed more realistic methods, called “Dynamic Traffic Assignment” that allow conditions on one segment to affect upstream and downstream segments.  But IBR modelers have clung to the out-dated, and demonstrably wrong “STA” methodology, even though dynamic traffic assessment models have begun to be developed for other projects in the Portland area, notably modeling traffic flows on I-205.

The Marshall Report

The Marshall Report, a detailed 32-page critique of the IBR’s traffic modeling, was commissioned by the community group Just Crossing Alliance.  You can read the entire Marshall report here:

 

[pdf-embedder url=”http://cityobservatory.org/wp-content/uploads/2024/10/Marshall_SDEIS_Modeling_Review_October2024.pdf”]

Moving the goalposts: Redefining traffic congestion

IBR re-wrote the definition of congestion to make I-5 traffic look worse

For decades, Oregon DOT has defined traffic congestion as freeway speeds below 35 MPH.

Now, for the Interstate Bridge project, IBR has moved the goalposts:  now any speed under 45 MPH is counted as “congested.”

The definition of “congested” matters because its central to claims that in the future there will be more “hours of congestion” than there are today.  But by changing the yardstick to count traffic traveling at up to 45 miles per hour as “congested,” IBR has artificially inflated the problem.

The determination is based on an unpublished, incomplete ODOT study that was supposed to be finished a year ago.  The new 45 MPH threshold contradicts WSDOT research showing freeways like I-5 maximize vehicle flow at 38.5 to 47 MPH.

IBR moved the goal posts on what is counted as “congestion”

One of the major problems the Interstate Bridge is supposed to fix is to reduce the number of hours of traffic congestion on I-5 between Portland and Vancouver.  But the project’s just released Draft Supplemental Environmental Impact Statement (DSEIS) shows that the two state highway departments have inflated their estimates of current and future traffic congestion by re-defining the threshold for what constitutes congestion.  In years past, Oregon has treated speeds of less than 35 miles per hour as “congested.”  But now, the DSEIS raises that threshold to 45 miles per hour—automatically inflating present and predicted future congestion.

The new definition is based on an incomplete, unpublished “White Paper.”

The decision to move to a 45 mile per hour threshold is contained in obscure section of the the project’s DSEIS, and has a very questionable basis.  The DSEIS says that the OregonDOT is “finalizing a white paper” to redefine congestion as speeds less than 45 MPH.  Oddly, the DSEIS says the white paper was to be finished in fall winter 2023—a year before the issuance of the DSEIS itself.  Plus, the DSEIS concedes that even that 45 MPH standard may be revised before the “white paper” is finalized.  Nonetheless, even though the report isn’t final, and might be revised, and should have been done by now, the DSEIS proclaims “The IBR program has defined congestion as speeds below 45 mph.

The Transportation Technical Report for the SDEIS offers this explanation of how they’ve changed the definition of what constitutes congestion.  You have to dig deep, it’s on page 498 of the 1,121 page technical report.

Congestion was speeds less than 35 MPH, now we’ve decided its lets than 45 MPH

Washington State says speeds under 40 miles per hour are optimal for maximizing traffic flow.

The new definition flatly contradicts the research and policy of the Washington State Department of Transportation.  WSDOT points out that based on published transportation research, freeways carry the maximum amount of traffic when average speeds are between 70 percent and 85 percent of the posted speed limit.  When cars travel faster, following distances increase, and the the road can actually carry fewer cars per hour than when speeds are slightly slower.  According to WSDOT, these slightly slower speeds make better use of the public investment in expensive road capacity—enabling as many people and vehicles as possible to travel in a corridor.

WSDOT research and policy say that freeway throughput is maximized when speeds are 70 to 85 percent of the posted speed limit.  Most segments of I-5 in North Portland have a posted speed limit of 55 miles per hour.  This means the optimal speed for the standpoint of maximizing traffic throughput on I-5 would be in the range of 38.5 to 47 miles per hour.

And, unlike the incomplete, unpublished “white paper” referenced by IBR for its new 45 mile per hour standard, the WSDOT analysis is contained in a technical report, now in its second edition, published for the past six years, entitled “WSDOT’s Handbook for Corridor Capacity Evaluation.”  Using a 45 mile per hour standard for evaluating congestion in the IBR project contradicts and violates the policies laid out in WSDOT’s handbook.  (Unsurprisingly, there’s no mention of WSDOT’s Corridor Capacity Handbook in the DSEIS transportation technical report).

 

The Week Observed, October 25, 2024

What City Observatory Did This Week

They’re digging in the wrong place:  A new, independent analysis by national traffic expert Norm Marshall of Smart Mobility, Inc., shows that the proposed IBR project fails to fix the real bottlenecks affecting I-5 traffic.  The Interstate Bridge Project proposes spending $7.5 billion to widen I-5, but misses the real bottleneck.  The Marshall report uses detailed traffic speed data to pinpoint the actual locations of slowdowns, and identify the freeway segments that are producing congestion.  The startling conclusion is that I-5 traffic is actually backed up because of capacity constraints outside the IBR project area, that won’t be fixed.  In the morning, traffic backs up from N. Lombard Street (while moving rapidly on the I-5 bridge).  In the afternoon, traffic backs up from N. Victory Boulevard

According to Marshall’s detailed analysis, widening I-5 at the Columbia River, as the IBR proposes will actually make traffic problems worse, especially in the morning peak hour, by funneling more traffic into these bottlenecks. The limited 3 lanes of I-5 in each direction between the Fremont Bridge and Lombard will continue to cause daily congestion.  Marshall also points out that the project’s elaborate “heat maps” are a classic example of “garbage-in, garbage-out” because they rely on the unrealistic and biased “static traffic assignment” model which fails to accurately capture how bottlenecks work.  This flawed traffic modeling means that the justification for the $7.5 billion is missing, that its environmental claims are wrong, and that its financial foundations are suspect.

Moving the goalposts:  The Interstate Bridge Project has re-written the definition of “congestion” to try to sell its $7.5 billion freeway widening plan. For decades, Oregon DOT has defined traffic congestion as freeway speeds below 35 MPH. Now, for the Interstate Bridge project, IBR has moved the goalposts: now any speed under 45 MPH is counted as “congested.”

The definition of “congested” matters because its central to claims that in the future there will be more “hours of congestion” than there are today. But by changing the yardstick to count traffic traveling at up to 45 miles per hour as “congested,” IBR has artificially inflated the problem.  The determination is based on an unpublished, incomplete ODOT study that was supposed to be finished a year ago. The new 45 MPH threshold contradicts WSDOT research showing freeways like I-5 maximize vehicle flow at 38.5 to 47 MPH.  This is the kind of Orwellian tactic used by the highway lobby to justify ineffective and environmentally devastating boondoggles.

Must Read

The mythical claim that most Americans are living “paycheck to paycheck.” A favorite talking point and social media theme is claiming most American’s are barely getting by.  Writing at SlowBoring.com Ben Krauss, takes a close look at the Lending Club survey claiming 60 percent of Americans say they live paycheck to paycheck.  It turns out the survey is highly subjective, and as a result, nearly impossible to interpret, or square with other data:  As xx points out:.

The first red flag is that the survey lacks a standardized definition of “living paycheck to paycheck.” Since the data is entirely self-reported, it relies on personal interpretation rather than objective financial metrics, making it less reliable than concrete measures of financial well-being like the poverty rate.

Those who have asked about the definitions and survey wording have been told that information is proprietary–something that hardly inspires confidence in the meaning or replicability of the results.  For some, living “paycheck to paycheck” may be coincident with poverty, but for others, it simply means that their paycheck is getting spent on everything from groceries to mortgage payments to vacations to investment accounts. There is, of course, real economic hardship, but for most Americans incomes are up, and have risen faster than living costs. We shouldn’t be elevating a questionable and secretive click-bait survey result above actual economic data.

A Better Way to Build Downtown.  Japanophile (and urbanophile) Noah Smith  has a well illustrated commentary arguing for more dense and vibrant urban commercial areas as a way to revitalize our downtowns.  He points to Japan’s Zakkyos—multi-story, street-facing commercial buildings that host a wide variety of shops and services, mostly provided by very small scale firms.  Urbanists regularly praise “mixed use development” but Smith argues that Zakkyo buildings  goes a step further to create dense concentrations of consumer choice.

Japan does things a bit differently from most of the world’s large, dense cities.  . . . Shop-top development, which is common in dense cities all over the world, puts apartment buildings on top of restaurants and stores. Zakkyo buildings, which are a kind of development seen mostly in Japan, have stores on all the floors.  My argument, basically, is that zakkyo buildings are at least partly responsible for many of the features that make Japanese cities such a consumer paradise

Mixing lots of commercial choices with dense urban housing maximizes the convenience, variety and discovery advantages that underpin great urban living.  The long-time American zoning fetish of widely separated uses (and catering to car-scaled development) has made it impossible to get this kind of rich density.  It’s time to revisit these assumptions.

Another explanation of Induced Travel:  For those who need one.  The most well documented by routinely ignored fact of urban transportation is the problem of induced travel.  Building additional highway lanes in dense urban areas doesn’t reduce congestion:  it triggers additional travel.  The science is now clear enough as to be called the “fundamental law of road congestion.”  But this reality is ignored or denied by road builders, who always assert that “one more lane” will fix traffic.

As if we needed more evidence on induced travel, Yale’s Climate Connections has a great explanatory interview with UCLA researcher Amy Lee.  She boils the induced travel phenomenon down to simple economic terms:

. . . the biggest factor that people consider when deciding how to get around is cost. That’s a matter of dollars, but also time – time is a really, really important factor in how we travel. When a particular roadway is congested, traveling on it can take a long time, or an unpredictable amount of time, which discourages people from using it.

Highway widening is kind of like putting travel on sale. It attempts to reduce congestion by expanding the amount of roadway supply, reducing the time cost of travel for travelers using it. So let’s say traffic kept me from going to a restaurant I really like that’s 20 miles away, but after the highway is widened, I can go there more frequently. Or I might choose a doctor in the next town over as opposed to the one in my neighborhood.

We rearrange our travel patterns because of highway expansions, and the new driving that results is what we call induced travel. And research has shown that because of induced travel, congestion returns to previous levels about five to 10 years after the highway is widened.

Time for a federal, “fix it first” mandate.  One of the long-running cons in the highway world is the maintenance backlog “bait and switch.”  Highway departments persistently plead pothole poverty, saying they need billions to repair or simply maintain deteriorating roads and bridges.  But anytime they’re given additional funds, they get plowed into massive highway expansion projects–doing nothing to erase the backlog, and actually making it worse.

Transportation for America says its time for the US Department of Transportation to act like the adult in the room:  essentially requiring states to maintain and repair what they’ve already got before they get additional funds for new capacity.  Ironically, this is almost exactly what bond markets require before they’ll lend money for toll roads or bridges:  the sponsoring agency has to show that they have an iron-clad financial plan for keeping the facility in tip-top shape.  Federal funds ought not go to the grasping wastrels in state highway departments who’ve long treated basic maintenance as a fund-raising gimmick, rather than a fundamental responsibility.

In the News

The Portland Mercury quoted Joe Cortright in its coverage of the denial of funding for the Rose Quarter project.

 

KGW-Television cited City Observatory’s Joe Cortright in its article on the federal government’s decision not to approve a requested $750 million grant for the I-5 Rose Quarter freeway widening project.

The Week Observed, October 18, 2024

What City Observatory Did This Week

Forecasting the impossible:  The case for the $7.5 billion Interstate Bridge Replacement project is based on deeply flawed traffic models that ignore the bridge’s capacity limits, and predict plainly unrealistic levels of traffic growth if the bridge isn’t expanded.  These grossly overestimated projections make future traffic look worse and overstate the need and understate the environmental and financial costs associated with freeway expansion.

The current I-5 bridge can carry no more than 5,000 vehicles northbound in the afternoon peak hour.  All of the available statistics, and every one of the experts that has looked at the bridge has concluded that it is already operating at its maximum capacity.

But Metro’s regional travel demand model, Kate, pretends that the bridge now carries more than 6,200 vehicles per hour–a thousand more cars and trucks per hour than can actually fit across the bridge. And the Kate model, used for the IBR environmental analysis, makes the  absurd prediction that peak hour PM traffic will increase further beyond its capacity—even if the IBR project isn’t built.

The Interstate Bridge Project’s Flawed Traffic Data.  The Interstate Bridge Replacement Project simply can’t tell the truth about current traffic levels or recent growth rates. IBR reports inflate the current level of traffic on I-5 bridges by nearly 5,000 vehicles per day.

The IBR has variously claimed 142,400 or 143,400 vehicles per average weekday in 2019. Meanwhile, ODOT’s automatic traffic recorder reports 138,780 per day for the same year. That’s a discrepancy of up to 4,620 vehicles per day—not exactly a rounding error when you’re justifying a multi-billion dollar project.

IBR reports falsely claim that I-5 bridge traffic is growing twice as fast as ODOT’s own data show.  IBR officials have exaggerated traffic levels and traffic growth rates to try to sell an over-sized, over-priced project.

Kate: Metro’s wildly inaccurate model overstates current traffic levels.   The case for the $7.5 billion Interstate Bridge Replacement Project is based on traffic projections from Metro’s “Kate” travel demand model. But there’s a huge problem: Kate doesn’t accurately model even current levels of traffic. The model has a high overall error factor, and importantly, consistently over-estimates traffic on the existing I-5 bridges.

Metro has prepared a validation report—not published on its website—showing the Kate model assigns vastly more traffic to I-5 than actually use the bridge. The model essentially adds 20,000 non-existent cars and trucks to I-5 each day in 2019—more than 6 million vehicles annually.  It’s hard to believe that Kate can predict future travel levels when it can’t accurately estimate current traffic volumes within a 20 percent error range.

In the News

Dissent published “Highway Robbery” Ben Ross and Joe Cortright’s article exposing the deep rot in traffic modeling used to justify highway expansion projects.

IBR: Forecasting the impossible

The case for the $7.5 billion Interstate Bridge Replacement project is based on deeply flawed traffic models that ignore the bridge’s capacity limits, and predict plainly unrealistic levels of traffic growth if the bridge isn’t expanded.  These grossly overestimated projections make future traffic look worse and overstate the need and understate the environmental and financial costs associated with freeway expansion.

The current I-5 bridge can carry no more than 5,000 vehicles northbound in the afternoon peak hour.  All of the available statistics, and every one of the experts that has looked at the bridge has concluded that it is already operating at its maximum capacity.

But, Metro’s regional travel demand model, Kate, pretends that the bridge now carries more than 6,200 vehicles per hour–a thousand more cars and trucks per hour than can actually fit across the bridge.

And the Kate model, used for the IBR environmental analysis, makes the  absurd prediction that peak hour PM traffic will increase further beyond its capacity—even if the IBR project isn’t built.

And IBR officials altered the outputs of the Metro model to produce an event higher—and more preposterous–prediction that the “No-Build” version of the bridge would somehow carry 6,900 vehicles per hour in the northbound peak in 2045. 

Forecasting the impossible

IBR traffic modeling is blind to the real capacity limits on the I-5 bridges; this is a common flaw in the kind of “static traffic assignment” models that Metro and IBR used;

Models that don’t accurately account for capacity limits are broken, and worthless for analyzing traffic conditions and deciding how to spend billions of dollars.  But the Oregon and Washington highway departments have chosen to use these flawed models to sell an oversized bridge.

These over-estimates-pretending that traffic volumes wildly exceed actual capacity are a critical gimmick for falsely portraying what happens if the $7.5 billion Interstate Bridge Replacement Project isn’t built.  They’re critically a way of hiding the “induced travel” that will come if the bridge is expanded:  by pretending that traffic will increase whether or not the I-5 highway is widened, IBR officials are concealing the pollution and traffic that comes from wider roadways.

The decision to use a traffic model that ignores the capacity constraints on the existing I-5 bridges exaggerates future traffic growth and congestion, and falsely conceals the negative environmental effects associated with a wider crossing.  Using an inaccurate, unscientific model, blatantly violates the National Environmental Policy Act.

The most obvious feature of the existing I-5 bridges over the Columbia River is the two narrow three-lane wide structures that carry highway from bank to bank.  There are just so many vehicles that can be fitted into these lanes.  The traffic data–confirmed by every expert that has looked at the bridge–is that the maximum peak hour capacity of the bridge has been reached, and can’t increase further.  For example, afternoon peak hour crossings on the bridge have been stuck at less than 5,000 vehicles per hour for the past two decades.

In spite of this obvious and well-documented limitation, Metro’s Kate travel demand model, which is the basis for the IBR’s environmental analysis, asserts that even if nothing is done, more and more cars will cross the bridge at the peak hour each year.  In fact, as we’ve documented previously, Metro’s Kate model—the basis for IBR traffic projections–simply fails to correctly estimate even the current levels of traffic on the I-5 bridges, assigning nearly 20,000 more daily trips to the bridges than they actually carry.

The problem of these over-estimated volumes is most acute for the peak hour.  Metro’s Kate model over-estimates the current level of traffic on the bridge–asserting that it carries over 6,000 vehicles per hour in the Northbound PM peak, even though traffic data show that flows are always less than 5,000 vehicles per hour.

The problem here is that Metro’s model simply fails to realistically account for the physical limits on traffic flow on the bridge.  The model creates a fictional alternative reality where the bridge somehow carries more and more peak hour traffic–even though the data, and the modelers themselves admit the bridge has long since reached its capacity.

Metro’s flawed Kate Traffic model predicts traffic exceeding capacity–an impossible outcome.

That inflated “no-build” estimate is a critical foundation of the phony case being made for expanding the I-5 bridges.  By exaggerating peak hour growth if nothing is done, the model makes it appear that traffic will be worse than it will actually ever be.  In addition, because environmental analyses use this exaggerated no-build traffic level (and resulting pollution) as their basis for comparison, they create the false perception that the “build” alternatives (which add massive amounts of road capacity) won’t stimulate additional trips, vehicle miles of travel, and pollution.

The Interstate Bridge Replacement (IBR) project, with its multi-billion dollar price tag, is founded on traffic projections that defy physical reality. This discrepancy between modeled predictions and actual capacity raises serious questions about the project’s justification and potential environmental impacts.

The I-5 Interstate Bridge is at capacity, and can’t add more traffic

All experts—and IBR—agree the I-5 bridges are at capacity at peak hours.  Every analyst who has looked at the I-5 bridges has concluded that they are effectively carrying as many vehicles per hour during peak periods as is possible.

  • Traffic count data show that PM peak hour volumes have been steady for the past twenty years.
  • Afternoon northbound peak hour volumes have been stuck at less than 5,000 vehicles per hour since 2000.
  • The project’s Environmental Impact Statement concedes that the maximum hourly capacity of the I-5 bridges is no more than 1,850 v/l/h or about 4,550 vehicles per hour (IBR Traffic Technical Report, Appendix A, Transportation Methods Report.).
  • IBR forecast officials explain that traffic levels on I-5 have grown more slowly than on I-205, “due to capacity constraints and extensive congestion over the Interstate [I-5] Bridge.” 
  • CDM Smith, the national traffic expert hired by ODOT and WSDOT in 2013 to forecast traffic concluded, “Traffic under the existing toll-free operating condition on the I-5 bridge reached nominal capacity several years ago, . . .  The I-5 bridge has little or no room for additional growth in most peak periods.”
  • None of this is a recent revelation:  peak traffic growth has been capacity constrained for decades.  Clark County’s Regional Transportation Council reported in 2018 that “The Interstate Bridge reached capacity during peak hours in the early 1990s.”

In spite of the universal agreement that the current bridges are at peak capacity during rush hours, Metro’s model claims that peak hour volumes will continue to increase even if nothing is built.  Let’s focus on the afternoon rush hour—northbound traffic from Portland to Vancouver, between 4 and 6 pm—the period of maximum daily traffic congestion.  State traffic count data show that about 4,800 vehicles crossed the I-5 bridges in the afternoon peak hour Northbound each day in 2019.  But Metro’s traffic model, Kate, which is the basis for IBR’s justification, and environmental analysis makes a false claim that more than 6,000 vehicles crossed the I-5 bridges northbound in the PM peak hour.

Projected peak hour  exceed physical capacity

The Metro model, which forms the basis of IBR’s planning, consistently predicts peak traffic levels on the I-5 bridge that exceed its demonstrated physical capacity of the bridge.

1. Current Capacity: The I-5 bridge can carry approximately 5,000 vehicles northbound in the PM peak hour, as evidenced by traffic count data. Here is a typical chart from IBR.  Maximum northbound traffic flows at 5pm were 4,810 vehicles.

 

2. Model Overestimation: Metro’s “Kate” model claims current traffic is currently (2019) over 6,290 vehicles per hour and predicts this will increase slightly to 6,375 by 2045.  Here is a screenshot of an Metro Excel spreadsheet summarizing the peak hour volumes for I-5 in 2019.  Northbound volumes for single occupancy cars, multiple occupancy cars, and medium and heavy trucks are highlighted and total 6,290 vehicles in the PM peak hour in 2019:

Metro spreadsheet obtained by public records request.  Highlighting not in original.  PM peak hour volume of 6,290 is the sum of 4,964 single occupancy cars, 1,011 multiple occupant cars, 240 heavy trucks and 76 medium trucks.

3. IBR’s Inflated Growth Estimates:  Consultants for the Interstate Bridge Replacement project altered the estimated traffic levels from Metro “Kate” model, something they call “post-processing.”  They recognized that Metro’s Kate model over-estimated current (2019) NB peak hour traffic levels–which they lowered to 5,740 vehicles from Kate’s 6,290.  The 5,740 figure still greatly exceeds actual traffic counts.  But while Metro’s Kate model allowed almost no growth in peak traffic in the No-Build through 2045, IBR’s “post-processing” allowed growth in the No-Build to increase to 6,905 vehicles per hour–more than 2,000 vehicles per hour beyond the actual physical capacity of the bridge.

IBR traffic modeling presentation, obtained by public records request (detail).  March 30, 2022, Slide Number 21.

In sum:  the IBR’s claims about peak hour traffic don’t mesh with actual data from traffic counts.  The Metro Kate Model and IBR “post-processed” data over-state current traffic levels significantly.  Both models assume that peak hour traffic will grow further in excess of capacity, and IBR’s “post-processing” while partly correcting for base year over-estimates, has an even higher predicted growth rate. These projections are not just optimistic; they are physically impossible given the current infrastructure.

As traffic expert Norm Marshall says, models like these that fail to recognize capacity limits are “Forecasting the Impossible.”  He explains Static Traffic Assignment modeling technique used by Metro and IBR

. . . allows modeled traffic volumes to exceed capacity. This misrepresents traffic not only on the over-capacity segment, but on downstream segments that the excess traffic could not really reach because it either would divert to other routes or be queued upstream.

Marshall, N. “Forecasting the impossible: The status quo of estimating traffic flows with static traffic assignment and the future of dynamic traffic assignment,” Research in Transportation Business and Management, https://doi.org/10.1016/j.rtbm.2018.06.002

Violating Federal Highway Administration guidance

Transportation experts have long known that failing to realistically account for capacity limits leads traffic models to grossly over-estimate traffic growth.  The Governmental Accountability Office and the National Academy of Sciences have both criticized this limitation of the traffic models of the type used by Metro and IBR.  The Federal Highway Administration (FHWA) explicitly requires that demand estimates realistically account for capacity limitations.

“Constraining demand to capacity. . . care must be taken to ensure that forecasts
are a reasonable estimate of the actual amount of 
traffic that can arrive within the analytical period . . .

Regional model forecast are usually not well constrained to system capacity”

IBR clearly hasn’t taken care to assure its forecasts predict only as much traffic as the roadway can handle.  The current modeling approach violated FHWA guidance, raising questions about the validity of the entire planning process.

Implications of overestimated peak hour traffic

Correctly estimating future peak hour traffic levels are the critical planning parameter for this project.  The consequences of IBR’s  inflated peak hour traffic projections are far-reaching:

1. Unjustified Expansion: By predicting traffic levels that exceed capacity, the model artificially creates congestion scenarios used to justify expanding freeway capacity.

2. A Distorted Environmental Assessment: Overstating traffic in the “no-build” scenario leads to an underestimation of the environmental impacts of the “build” option, potentially violating NEPA requirements. By exaggerating traffic and congestion in the “no-build” scenario, the IBR understates the true enviornmental effects of the build scenario.

3. Ignoring Historical Trends: The models disregard the fact that peak hour I-5 bridge traffic has not increased since 2005 due to existing capacity constraints, a point acknowledged by IBR itself.

IBR uses the euphemism “demand volumes” to hide its predictions that traffic will exceed capacity

IBR uses the term “demand volumes” to describe traffic levels that exceed physical capacity.   This is a euphemism to conceal the fact that these are not predictions of actual levels of travel, but are modeled predictions of the number of vehicles that might use the bridge if there were no capacity constraints.  The Metro RTDM model allows predicted traffic levels to exceed highway capacity.  The SDEIS repeatedly uses the term “demand volumes” in its Purpose and Need Statement (two instances) and in its Traffic Analysis (four instances).  This terminology allows for projections that exceed physical capacity, but it’s a concept at odds with reality. In practice, traffic demand is always constrained by available capacity.

False models are no basis for multi-billion dollar decisons

The IBR project’s reliance on traffic projections that exceed physical capacity undermines its credibility and raises serious questions about its necessity and environmental impact. As stewards of public resources and our environment, we must demand planning based on reality, not inflated projections.

It is imperative that the IBR team address these discrepancies and provide a clear, factual basis for their projections. Without this, we risk allocating billions of dollars to a project that solves imaginary problems while potentially creating real environmental and fiscal issues.

The future of our regional transportation system and the responsible use of public funds depend on a honest, data-driven approach to infrastructure planning. It’s time for the IBR project to align its projections with reality and provide the transparent, accurate analysis that the public deserves.

Kate: Metro’s wildly inaccurate model overstates current traffic levels

The case for the $7.5 billion Interstate Bridge Replacement Project is based on traffic projections from Metro’s “Kate” travel demand model.  But there’s a huge problem:  Kate doesn’t accurately model even current levels of traffic. 

The model has a high overall error factor, and importantly, consistently over-estimates traffic on the existing I-5 bridges. 

Metro has prepared a validation report—not published on its website—showing the Kate model assigns vastly more traffic to I-5 than actually use the bridge. 

The model essentially adds 20,000 non-existent cars and trucks to I-5 each day in 2019—more than 6 million vehicles annually. 

The Metro forecast prepared for the Columbia River Crossing showed the same problems, over-predicting traffic growth by a factor of four between 2005 and 2019.  The model claimed growth would be 1.3 percent per year; the reality was 0.3 percent growth.

Ironically, Oregon and Washington have paid private sector firms to develop much more accurate models of regional traffic–but they’ve excluded these more realistic models from the IBR environmental impact statement–in likely violation of the National Environmental Policy Act.

An indispensable part of the sales pitch for wider highways is the seemingly precise and statistically intimidating results of computerized travel demand models.  These models purport to predict, with great certainty, future traffic levels decades from now.  In the hands of state highway departments, such models are routinely used to “prove” that traffic is increasing inexorably, that if nothing is done, congestion will become intolerable, and paradoxically, that wider roads won’t actually stimulate any more traffic.  In reality, the models are an intimidating fiction, like the Wizard of Oz’s flaming avatar, designed to frighten and cajole.  And just as in Oz, the real manipulation is being done by the man behind the curtain.

The man behind the curtain is operating Metro’s “Kate” travel model.

In the high-stakes game of justifying multi-billion dollar infrastructure projects, traffic forecasts are a computer-driven trump card for project proponents. Traffic modelers use complex and impenetrable computer models to generate seemingly precise estimates of future traffic levels, which they use as a cudgel to push for over-sized highways.  But a close look at the models shows that they are biased and wrong, and systematically over-state traffic, not just in the future by now.  Metro’s much-hyped “Kate” regional travel demand model dramatically over-estimates current levels of I-5 traffic, as well as projecting physically impossible growth in future years.  The Interstate Bridge Replacement (IBR) project offers a textbook case of modeling gone awry, with potentially far-reaching consequences for taxpayers and the environment.

Kate doesn’t accurate describe the present, and can’t predict the future

At the heart of the IBR’s justifications lies Metro’s regional travel demand model–dubbed “Kate.” But our analysis reveals that Kate has a penchant for fiction especially when it comes to I-5 bridge traffic.

Poor Calibration.  The test of a model is whether it can accurately reflect reality.  For transportation models, professionals talk about “calibration” whether the predictions of the model match actual real world traffic counts.  Metro’s Kate Travel Demand model has a high overall error factor.  We measure overall modeling error using a statistical metric called “Room Mean Squared Error”—RMSE—which tells how far off the overall model is in matching actual data.  Metro’s Kate model has a RMSE of 14.5 percent, meaning that on average, the model gets current traffic levels right within only about a 15 percent margin.  Keep in mind that calibration asks whether a model can accurately predict current traffic levels.  Importantly, the 14.5 percent RMSE for the Metro model is much higher than for other Portland area transportation modeling efforts.  Here’s a table showing the RMSE for several other models.

Comparison of Travel Demand Model Validation
Model (Year) Calibration Year Scope Metric Error (RMSE)
Metro/Kate (2017) 2015 32 Regional Cutlines AWDT 14.5%
Stantec/IBR Level 2 (2023) 2015 32 Regional Cutlines AWDT 2.5%
CDM Smith/CRC IGA (2013) 2010 11 Regional Cutlines Hourly 2.5%
CDM Smith/CRC IGA (2013) 2010 I5, I205 Bridges Hourly 0.8%

The other models shown here, which cover the same geography as the Kate model, have RMSE error factors of less than one percent to two-and-one-half percent.  That means the error factor in the Kate model is six to fifteen times larger than for these other models.  Metro’s Kate model is demonstrably less accurate and less well-calibrated than other models.  Yet IBR officials have chosen to rely on Kate in their environmental analysis.

Overestimation: As bad as it is in predicting overall traffic levels in the region, Kate is demonstrably worse in predicting traffic on the bridges across the Columbia River.  Kate consistently overestimates traffic on the I-5 bridge, by almost  20 percent. In 2019, for instance, the Kate model says there were  164,500 average weekday trips across the I-5 bridge. The reality? A much more modest 138,530, according to ODOT’s own traffic recorders.

Estimates of Calendar year 2019, Average Weekday Traffic, I-5 Bridge

Source Estimate Error
ODOT, Traffic Count data 138,530 0
Metro, Kate Travel Demand Model 164,500 +18.7%

This fact is buried in a technical report—not published on Metro’s website—which shows that the Kate model dramatically overstates the current level of traffic.  This shows the model is poorly calibrated and can’t even reflect current reality—much less accurately predict the future.

Exaggerated Growth Rates:  Kate is the just the latest version of Metro’s traffic-inflating models.  Kate’s predecessor “Ivan” predicted that if the Columbia River Crossing project (the predecessor to IBR) weren’t built (spoiler—it wasn’t) that I-5 bridge traffic would grow at a rapid  1.3% annual growth rate from 2005 to 2030. The actual growth rate from 2005 to 2019? A paltry 0.3% per year. Metro’s travel model predicts four times as much traffic growth as actually occurred:  That’s not just missing the mark; it’s not even in the same ballpark.  The current Kate model also wildly over-estimates future traffic growth.

Millions of Phantom Cars and Trucks: The discrepancy between Kate’s predictions and reality isn’t just a statistical anomaly. It translates to over 20,000 “phantom” vehicles per day that exist only in the model’s imagination. That’s more than 6 million non-existent trips per year.

A better calibrated model produced dramatically different results

While IBR officials take pains to paint the “Kate” travel demand model as an objective, scientific mechanical predictor, its actually anything but.  The complex system of equations that compose the model depend on settings and inputs chosen by modelers.  In this respect, its not unlike an Excel spreadsheet:  If you enter different numbers in one cell, you get different results elsewhere.  Other modelers, starting with the same Metro Regional Travel Demand model, plugged in different parameters, and produced a vastly more accurate forecast of I-5 traffic growth.  In 2013, Oregon and Washington DOTs paid modeler  CDM Smith model, commissioned for an investment-grade analysis of the Columbia River Crossing, tells a different story. After recalibrating Metro’s model, CDM Smith’s predictions aligned much more closely with reality, forecasting a 0.3% annual growth rate that matches observed data.  More recently, IBR hired Stantec to produce a version of the model to estimate toll revenues; it too is vastly more accurate than the Metro model. (See Table above).  The big question for public officials–and ultimately the courts–is why are ODOT and WSDOT using a model with a vastly larger error factor to plan a multi-billion dollar project, instead of more accurate models Oregon and Washington have already paid for?

Biased traffic projections to justify a bloated project

Why does this matter? Because these inflated numbers are being used to justify a massive, expensive project. The supposed reason that $7.5 billion in wider highway lanes and rebuilt interchanges are needed is to accommodate phantom traffic that exists only in the model.  More realistic traffic projections would enable a much cheaper, less environmentally devastating project.  By overstating current traffic and future growth, the IBR project is:

  • Exaggerating the need for expanded capacity
  • Potentially overbuilding infrastructure at taxpayer expense
  • Understating the environmental impacts of the “build” alternative by comparing it to an inflated “no-build” scenario

Concealing Kate’s inaccuracies

Metro and IBR staff are aware of the problems with the “Kate” model, but have largely buried information about its bias and inaccuracy in other technical documents.  Metro produced a “validation” report for Kate in 2017, but does not publish this crucial document on its website.  For those who want to see the report, we’ve attached a copy we obtained via public records request below.  And despite these glaring issues, Metro and the IBR continue to use the poorly calibrated Kate model “for planning purposes.” It’s hard not to conclude that they prefer these higher forecasts because they justify a larger project and conceal the travel-inducing effects of expanded capacity.

When questioned about these discrepancies, one can almost hear the IBR planners channeling the Great and Powerful Oz: “Pay no attention to that man behind the curtain!” But unlike in the movie, the wizard behind IBR’s curtain isn’t a harmless humbug. Instead, it’s a flawed modeling process with the potential to waste billions in taxpayer dollars and reshape our region’s transportation landscape based on fantasy rather than fact.

Time for a reality check

The IBR project is betting billions of taxpayer dollars on traffic forecasts that don’t stand up to scrutiny. It’s time for a reality check. We need:

  • An independent audit of the traffic modeling proces
  • Transparent reporting of model inputs, assumptions, and output
  • A reevaluation of the project’s scope based on realistic traffic projections

Until then, the IBR project risks building a bridge to nowhere – or more accurately, a bridge to a future that exists only in the realm of faulty models and phantom traffic. It’s time to pull back the curtain and expose this “wizard” for what it really is: a collection of flawed assumptions and inflated projections masquerading as a scientific process.

Appendix:  2017 Kate Validation Report

Here is a copy of Metro’s “2017 Kate v1.0 Trip-Based Demand Model Validation Report for Base Year 2015.”  This report does not appear on the Metro website (oregonmetro.gov).  The report is still marked “DRAFT” years later, and no “final” version has ever been released.

[pdf-embedder url=”http://cityobservatory.org/wp-content/uploads/2024/10/Kate_Validation_Report_August2017.pdf”]

The Interstate Bridge Project’s Flawed Traffic Data

The Interstate Bridge Replacement Project simply can’t tell the truth about current traffic levels or recent growth rates.

IBR reports inflate the current level of traffic on I-5 bridges by nearly 5,000 vehicles per day

IBR reports falsely claim that I-5 bridge traffic is growing twice as fast as ODOT’s own data show

IBR officials have exaggerated traffic levels and traffic growth rates to try to sell an over-sized, over-priced project.

It’s important to note that this is actual, recorded data, gathered by the Oregon Department of Transportation, and published on its traffic counting website.  If IBR officials can’t be trusted to accurately report current and historical data, and when they instead choose to inaccurately inflate traffic counts and claim traffic is growing twice as fast as their own data show, it raises serious concerns about whether they can be trusted to accurately project future traffic levels–a process that is inherently more difficult, and critically, largely shrouded from public view.

The Interstate Bridge Replacement (IBR) project, a massive $7.5 billion undertaking to replace the I-5 bridges over the Columbia River, is built on a foundation of questionable traffic projections. As we’ve seen time and again with megaprojects, errors in traffic modeling can lead to overstated needs, financial boondoggles, and understated environmental impacts. The IBR project seems to be following this well-worn path.

The importance of getting traffic numbers right

Traffic counts and modeling aren’t just a technical exercise—they’re the cornerstone of the entire project. Traffic levels define the need, justify the size, evaluate alternatives, and determine financing.  Understanding present and future traffic levels are also crucial for assessing environmental impacts. As the Federal Highway Administration notes, “travel and land use forecasting is integral to a wide array of corridor and NEPA impact assessments and analyses.” In other words, if the traffic forecasts are wrong, the entire environmental impact assessment is compromised.  Current traffic data and recent traffic growth trends need to be accurate in order to create accurate forecasts of future activity–and IBR officials have exaggerated traffic levels and traffic growth to sell their project.

IBR can’t even report current traffic count data accurately

One would think that counting cars on a bridge would be straightforward. Yet, the IBR project can’t seem to agree with itself—or with the highway department’s own  traffic recorders—on how many vehicles cross the I-5 bridge daily.

The IBR has variously claimed 142,400 or 143,400 vehicles per average weekday in 2019. Meanwhile, ODOT’s automatic traffic recorder reports 138,780 per day for the same year. That’s a discrepancy of up to 4,620 vehicles per day—not exactly a rounding error when you’re justifying a multi-billion dollar project.

Average weekday traffic for each month in 2019  is shown in second column of the right-hand panel of this table, downloaded from ODOT’s own traffic reporting website.  The average weekday traffic for the twelve months January through December 2019 is 138,780 vehicles per weekday.

This isn’t the first time ODOT and WSDOT have played fast and loose with traffic numbers. During the Columbia River Crossing project from 2008 to 2011, they overstated 2005 traffic levels —a fact they were forced to admit in federal court.

IBR exaggerates recent traffic growth

Not only does the IBR technical work get recent traffic levels wrong, it also grossly overstates the rate of growth in traffic across the I-5 bridge.  The study focuses on the four-years prior to the pandemic—2015 to 2019.  The IBR’s “Level 2” traffic study claims traffic on the I-5 bridge increased by 1.1 percent annually between 2015 and 2019. However, ODOT’s own official data shows the actual growth rate was only 0.55%—half of what the IBR claims. This isn’t just a minor discrepancy; it’s a fundamental misrepresentation of traffic trends that could significantly impact the project’s justification and design.

The inaccurate traffic count data leads the Stantec Level 2 study to overstate the recent rate of growth across the I-5 bridges.  The Level 2 study claims that between 2015 and 2019, traffic increased by 1.1 percent per year. 

The average weekday river crossings along the I-5 and I-205 Bridges since 2015 are presented in Figure 2-6. Between 2015 and 2019, the traffic on the I-5 Interstate Bridge increased at an annual rate of approximately 1.1% . . .
Stantec, Level 2 Report, page 2-9

According to the average weekday traffic data reported on the ODOT automatic data recorder website, the actual rate of increase was only half as much—0.5 percent.   We examined actual data reported on ODOT’s website (https://www.oregon.gov/odot/data/pages/traffic-counting.aspx) for the Automated Traffic Recorder for  the I-5 Interstate Bridge.  In 2015, average weekday traffic was 135,696 vehicles per day.  In 2019, average weekday traffic was 138,700 vehicles per day.  This represents an annual rate of increase of 0.55 percent per year, half the rate claimed in the Stantec Report.

The difference in growth rates is a crucial point that highlights potential issues with the IBR project’s traffic projections.  The failure to accurately report recent traffic growth has important implications and consequences:

    • The IBR’s claimed growth rate is twice the actual rate based on official ODOT data.
    • This discrepancy is significant because growth rates are often used to project future traffic volumes, which in turn justify the need for and scale of transportation projects.
    • Overestimating the growth rate leads to inflated projections of future traffic.
      • This could result in overbuilding infrastructure, wasting public resources, and potentially creating unnecessary environmental impacts.
      • It might also affect the financial viability of the project, as toll revenue projections are based on these inflated growth rates.

This difference in growth rates is not just a minor statistical quibble. It represents a fundamental issue with how the IBR project is analyzing and presenting traffic data. If the project is consistently overestimating traffic growth, it could lead to a significantly oversized and more expensive project than what is actually needed. This highlights the need for transparent, accurate, and verifiable traffic data and projections in planning such a massive infrastructure project.

With a price tag of up to $7.5 billion, the IBR would be the most expensive transportation project in the region’s history. It’s crucial that decisions about such a massive investment are based on accurate, consistent data. Yet, what we’re seeing is a pattern of inflated numbers, inconsistent baselines, and opaque methodologies. The discrepancies and inconsistencies in the IBR’s traffic modeling raise serious questions about the project’s foundation. If we can’t trust the basic traffic counts, how can we trust the complex projections built upon them?