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.

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.

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).

 

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).

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.

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.

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:

1. • 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?

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.

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.