Oregon and Washington have commissioned not just one forecast of future traffic levels on I-5 and I-205, but three different forecasts.

IBR officials are clinging to the one forecast that is the least accurate, and most error-prone, and have chosen to ignore two more accurate forecasts.

IBR relies on Metro’s Kate Model, which has an error factor of 14.5 percent and which over-estimates I-5 traffic by almost 20 percent.

IBR’s DSEIS makes no mention of the Stantec Level 2 forecast (with an error factor of 2.5 percent), or the CDM Smith Investment Grade Forecast (with an error factor of 0.8 to 2.5 percent).

The two states have paid $1.5 million for the CDM Smith Forecast and nearly $800,000 for the Stantec Level 2 Forecast.

Using a less accurate forecast and ignoring or suppressing more accurate forecasts in the EIS violates the National Environmental Policy Act.

The Oregon and Washington highway departments have paid for three traffic studies predicting future travel on the I-5 bridge.  Their Draft Supplemental Environmental Impact Statement uses just one of them, and suppresses and ignores the other two studies because they inconveniently show that a tolled I-5 bridge will carry less traffic in future decades than it does today–contradicting the claim that the freeway needs to be widened and seven interchanges rebuilt at a cost of $7.5 billion.  The DSEIS claims traffic on I-5 will increase from less than 140,000 today to 164,500 vehicles.  The other two studies show tolling will permanently reduce traffic to well below today’s traffic levels. The two studies they’ve suppressed and ignore have lower error factors than the one study they’ve chosen.

BR officials have “cherry-picked” their forecast to match their biases.  IBR clearly prefers the less accurate Metro model because it creates the illusion that a larger project is needed, and creates a false baseline of high levels of traffic for the No-Build scenario, leading the DSEIS to significantly understate the negative environmental effects of the build alternative.  Choosing not to use more accurate models when they are available is a violation of the National Environmental Policy Act—which governs the DSEIS.

IBR’s Draft Supplemental Environmental Impact Statement continues to use the poorly calibrated Metro Regional Travel Demand Model “for planning purposes” even though it substantially over-states actual traffic on the I-5 bridge.  It seems clear that Metro and IBR prefer these higher forecasts because (a) they justify a larger project with more vehicle capacity, and (b) they create an inflated “no-build baseline” that systematically conceals or understates the travel-inducing environmental effects of the build alternative.

The other two studies, an “investment grade analysis” prepared by CDM Smith at a cost of $1.5 million, a “Level 2” study prepared by another firm, Stantec, both offer a very different picture of future traffic levels on a tolled I-5 bridge.  These studies show tolling will permanently depress traffic levels on the I-5 bridge, and divert tens of thousands of cars to the parallel (and free) I-205 bridge.  The financial and environmental effects of this massive diversion are not considered in the DSEIS.

IBR chose to use the least accurate model for the DSEIS

Most importantly, IBR has chosen to use the least accurate of the three models in the DSEIS.  The error factor for the Metro model used to generate the IBR’s traffic forecasts is six to ten times higher than for the other two models, and has been shown to systematically over-predict traffic on I-5.  IBR’s own Stantec Level 2 study  concludes that the Metro model overestimates traffic levels on I-5:

While the calibration of the assignment model was adequate for planning purposes, some limitations were identified in the RTDM assignment process that resulted in overestimated speeds and underestimated travel times along the I-5 and I-205 corridors near the river crossings. As such, additional refinements were performed to the base year 2015 traffic assignment to improve alignment with the observed data. These refinements were performed outside of the RTDM environment, in a base year toll model prepared using RTDM output like demand matrices, highway network, and relevant parameters. 

Stantec (https://www.interstatebridge.org/media/sh2lube2/ibr_level-2_tr_report_final_remediated.pdf), page 3-5. (emphasis added)

Stantec’s Level 2 study corrected for the over-prediction on I-5, and produced a much smaller error.  Stantec calibrated its model to the same 2015 base data used in the Metro Kate modeling.  Stantec reported a 2.5% RMSE (Root Mean Square Error), just about one-sixth of the error factor for the Metro model.  The Stantec version of the model calibrated to within 1 percent of I-5 bridge traffic levels, compared to the 18 percent over-estimate in the Metro “Kate” model.

Note: “AWDT” is average weekday traffic. 

Sources:

Using a less accurate forecast violates NEPA

Using a less accurate forecast, when a more accurate one is available is a violation of NEPA.  In one relevant case, court’s found USDOT violated the law by failing to use newer, more accurate forecasts when they were available.

. . . [w]hile NEPA does not require an agency to update its population forecasts whenever new forecasts become available, it ordinarily may not rely on outdated forecasts when it sets out to prepare an EIS even though more recent forecasts from the agency’s own experts are readily available. Defendants’ decision to do so here was error.

Conservation Law Found. v. Fed. Highway Admin., 2007 WL 2492737, at *22 (D.N.H. August 30, 2007)

THE DSEIS conceals or omits more accurate forecasts of I-5 traffic

The Interstate Bridge Project has gone out of its way to omit any reference to either the CDM Smith Investment Grade Analysis or the Stantec “Level 2” traffic and revenue study from the Draft Supplemental Environmental Impact Statement.  Neither of these documents is cited or mentioned in the project’s 1,121 page “Transportation Technical Report” which purports to document all of the data, analysis and methodology behind the traffic claims in the DSEIS.  What this signals is that the IBR team and its consultants have explicitly failed to acknowledge or reconcile the substantial differences between these two forecasts and the forecasts they chose to include in the DSEIS.  What this means is that the IBR project cannot legitimately claim that these two studies have been taken into account int he preparation of the DSEIS.  This, on its face, is a violation of the legal requirements that when agencies have more recent or superior data, that they include it in the analyses, and that the EIS be based on an objective, scientific analysis of relevant data.

For reference, here are the two studies, neither of which is included in the DSEIS:

The Stantec Level 2 study ($787,000) is here:

The CDM Smith Investment Grade Analysis ($1.5 million):

IBR Traffic Forecasts Violate Portland Region’s Climate Commitments

Portland’s adopted Regional Transportation Plan commits the Metro area to reduce total vehicle miles traveled by 12 percent over the next twenty-five years.

But the traffic forecasts used to justify the $7.5 billion Interstate Bridge Replacement (IBR) Project call for more than a 25 percent increase in driving over that same time period

The RTP is required under state law to plan for a reduction in VMT per capita; the RTP is the way that regional and local governments show they comply with these state climate requirements

But the IBR planning is predicated on a world where we drive much more and not any less.

Projects like the IBR are required by state and federal law to be consistent with the adopted Regional Transportation Plan, but they are being planned for traffic levels that flatly violate that plan and state requirements.

The Interstate Bridge Replacement project’s traffic forecasts are on a collision course with reality – and with legally binding climate commitments. While the Portland region has adopted ambitious goals to reduce driving and greenhouse gas emissions, IBR’s plans assume we’ll do exactly the opposite, projecting a massive 26-27 percent increase in vehicle miles traveled (VMT). This disconnect isn’t just poor planning – it may violate federal law.

State law and Metro’s RTP commit the region to reducing total driving by 12 percent

Let’s start with the legal requirements. Metro, Portland’s regional government, has adopted a Climate Smart Strategy calling for a 75 percent reduction in greenhouse gases. The state’s Climate Friendly and Equitable Communities (CFEC) rules require Metro to reduce per capita vehicle miles traveled by 35 percent between 2005 and 2050. These aren’t aspirational goals – they’re legal requirements incorporated into Metro’s federally mandated Regional Transportation Plan (RTP), adopted in November 2023.

Under state land use regulations, Metro is required to adopt a Regional Transportation Plan (“RTP”) in which Vehicle Miles Traveled (“VMT”) declines by 30 percent from 2005 levels by 2045.  The Climate Friendly and Equitable Communities Rule OAR 660-012-0160(6) provides:

Metro shall adopt a regional transportation plan in which the projected vehicle miles traveled per capita at the horizon year using the financially-constrained project list is lower than the estimated vehicle miles traveled per capita at the base year by an amount that is consistent with the metropolitan greenhouse gas reduction targets in OAR 660-044-0020. [emphasis added]

Metro’s adopted RTP promises to meet this goal:

By 2045, the plan, together with advancements in fleet and technology, is expected to reduce VMT per capita of light-duty household vehicles by 39 percent (compared to 2005 levels) and by 31 percent from (compared to 2020 levels).

Metro 2023 Regional Transportation Plan, Appendix J. page 9.

The per capita reduction translates into a real reduction in total driving over the next two decades.  The math is simple: to meet these targets, the region needs to hold total vehicle miles traveled at about 12 percent below current levels through 2045, even as population grows. Metro’s RTP specifically projects a 31 percent reduction in per capita VMT from 2020 levels by 2045.

IBR traffic forecasts plan for 36 percent more driving

But IBR’s traffic forecasts live in an alternate universe where these policies don’t exist. The project’s Supplemental Draft Environmental Impact Statement (SDEIS) projects that regional VMT will balloon from 43.1 million daily miles today to 58.8 million by 2045 – a 36 percent increase that assumes driving per person will remain essentially unchanged.

Here are the details:  The DSEIS claims that base level of driving in the Metro area was about 43.1 million miles in 2015:

The DSEIS summarize the results of its modeling to show that the region will drive about 58.8 million miles in 2045.

This represents annual VMT growth of about 1 percent per year, and essentially no-per capita decline in VMT, completely at odds with adopted regional policy.  Traffic forecasts for the area in and near the IBR project  tell the same story. IBR projects VMT in the “study area” will jump from 11.7 million daily miles to 14.2-14.3 million – an increase of roughly 22 percent. This growth directly contradicts Metro’s RTP, which calls for reducing total regional VMT about 12 percent in order to achieve the mandated reduction in VMT per capita of more than 30 percent.

The SDEIS Leaves out Oregon climate regulations

Perhaps most telling is what’s missing from IBR’s climate analysis. While the SDEIS includes a lengthy inventory of state climate policies, it completely ignores Oregon’s Climate Friendly and Equitable Communities (CFEC) rules requiring Metro to reduce per capita VMT by 30 percent. This selective amnesia is hardly surprising – acknowledging these requirements would expose how fundamentally IBR’s traffic projections conflict with binding regional commitments to reduce VMT.

This isn’t just about numbers on a spreadsheet. By assuming away adopted climate policies, IBR creates a self-fulfilling prophecy: project a future of ever-increasing car dependence, then build massive infrastructure to accommodate it. This approach not only undermines regional climate goals but also violates the National Environmental Policy Act’s requirement that environmental analyses be based on reasonable assumptions consistent with adopted plans and policies.  NEPA requires that the EIS demonstrate consistency with adopted State and local statues and plans (40 C.F.R. § 1506.2(d)). Specifically, an EIS must evaluate “[p]ossible conflicts between the proposed action and the objectives of Federal, regional, State, and local . . . land use plans, policies and controls for the area concerned.” 40 C.F.R. § 1502.16(c) (1978). “Where an inconsistency exists, the statement should describe the extent to which the agency would reconcile its proposed action with the plan or law.” 40 C.F.R. § 1506.2(d) (1978).  The Draft Supplemental Environmental Impact Statement fails to identify this conflict with Oregon climate regulations and the Metro RTP, and also therefore fails to explain how it will reconcile its proposed action to these plans.

IBR officials might argue that their much higher traffic projections are somehow more realistic forecasts of future behavior. But this misses the point entirely. The region has made legally binding commitments—codified in its federally required Regional Transportation Plan—to reduce driving to achieve climate goals. The National Environmental Policy Act and federal transportation planning regulations require that projects like the IBR be consistent with this adopted policy framework, not against a hypothetical future where we abandon our climate commitments.

The solution is straightforward but would require a fundamental rethinking of the project: IBR must revise its traffic forecasts to align with adopted regional policies as required by federal and state law. This means lowering future VMT levels to about 12 percent below today’s traffic levels, not more than 25 percent higher as in the current modeling.

Until then, IBR’s traffic forecasts remain an exercise in illegal magical thinking – assuming away binding climate commitments to justify a massive highway expansion. It’s an approach that not only fails to meet legal requirements but also locks the region into precisely the car-dependent future we’ve committed to avoiding.

The choice is clear: either revise the project to align with regional climate commitments, or admit that IBR represents an abandonment of those goals. What we cannot do is continue pretending that we can meet our climate targets while building infrastructure designed for ever-increasing levels of driving.

The $7.5 billion Interstate Bridge Replacement Project’s two-decade old “Purpose and Need” statement is simply wrong, and provides an invalid basis for the project’s required Environmental Impact Statement.

Contrary to claims by project proponents, the “Purpose and Need” statement isn’t chiseled in stone, rather it is required to be evolve to reflect reality and better information.  Yet IBR is relying on a 2005 purpose and need statement that rests on exaggerated traffic forecasts that have been proven wrong.

The IBR’s 2005 Purpose and Need Statement (still forms the basis for the 2024 SDEIS) claimed the I-5 needed to accommodate 1.7 percent more vehicles each year.  In reality, traffic growth has been less than a fifth of that amount, 0.3 percent from 2005 to 2019.

For decades, highway builders have been pushing a “predict and provide” paradigm, pretending that we needed to plan for an ever-increasing flood of vehicle traffic, and threatening gridlock if highways weren’t expanded.  But these self-serving predictions have consistently proven wrong.

Law and policy require that the “Purpose and Need” statement be reasonable, and not drawn so narrowly as to exclude alternatives, and that the statement evolve over time as conditions change. But IBR is using, nearly unchanged, a two-decade old statement that falsely claims that I-5 must accommodate ever greater traffic.

IBR officials are clinging to an out-dated and simply incorrect purpose and need statement to inflate the size of the project, and to rule out lower cost alternatives with fewer environmental impacts, in violation of NEPA.

In the world of mega-infrastructure projects, few things are more important than accurately defining the problem you’re trying to solve. For Portland’s proposed Interstate Bridge Replacement project, that definition comes in the form of a “Purpose and Need” statement – a crucial document required by the National Environmental Policy Act (NEPA). This statement isn’t just bureaucratic paperwork – it’s the legal foundation that shapes the entire environmental review process. Under NEPA, the Purpose and Need statement determines which alternatives must be studied and which can be eliminated from consideration. It essentially sets the parameters for what counts as a potential solution.

The current Interstate Bridge Replacement (IBR) project is recycling, wholesale, a Purpose and Need statement originally drafted in 2006 for its predecessor, the Columbia River Crossing. That document’s central claim – that daily traffic demand would grow by more than 35 percent over 20 years – has proven wildly inaccurate. Rather than growing at the predicted rate of 1.7 percent annually (later revised to 1.5 percent), actual traffic on the I-5 bridge has grown at just 0.3 percent per year from 2005 through 2019, and an even lower 0.1 percent rate from 2005 to 2023.

This isn’t just a technical detail – it’s fundamental to the entire environmental review process. Under NEPA, agencies must rigorously explore and objectively evaluate all reasonable alternatives that could meet the project’s purpose and need. By vastly overstating future traffic growth in its “Purpose and Need” statement, the project artificially constrains the range of possible solutions, effectively mandating an oversized project while eliminating potentially more modest and less environmentally damaging alternatives from consideration. In essence, the exaggerated traffic projections become a self-fulfilling prophecy – by claiming we need infrastructure sized for phantom traffic growth, the project excludes more modest solutions from even being studied.

The Purpose and Need Statement must reasonable, not narrow

This matters because federal environmental law requires that projects consider a reasonable range of alternatives. As the 7th Circuit Court of Appeals noted in a key decision, it is “contrary to NEPA for agencies to contrive a purpose so slender as to define competing ‘reasonable alternatives’ out of consideration (and even out of existence).” Yet that’s exactly what appears to be happening here – by defining the project’s “need” as accommodating 35 percent more vehicles in twenty years, when all evidence suggests we won’t see anywhere near that growth, the IBR effectively eliminates smaller-scale alternatives from consideration.

The Purpose and Need Statement should evolve—but hasn’t

The federal Department of Transportation’s own guidance recognizes that Purpose and Need statements should evolve as new information becomes available. Their NEPA implementation guidelines explicitly state that “the purpose and need section of the project may, and probably should, evolve as information is developed and more is learned about the project and the corridor.” Yet despite having nearly two decades of actual traffic data that contradicts their original assumptions, the IBR team has chosen to simply copy and paste the old statement rather than update it to reflect reality.

And the old purpose and need statement has been proven hopelessly wrong.  In 2005, the Purpose and Need Statement claimed traffic would increase “more than 40 percent in the next twenty years” implying an annual growth rate of traffic of 1.7 percent per year.  The 2008 Purpose and Need Statement downgraded that to 1.5 percent per year, and the “Re-evaluated” purpose and need statement adopted in 2022 made exactly the same claim.  Now, with the passage of time, we know that actual traffic growth, even in the “normal” times prior to the Covid-19 pandemic, was less than one-fifth as fast–about 0.3 percent per year.  And none of the forecasts that have been done since the original purpose and need statement confirm its extremely high growth rate.

This isn’t just about traffic forecasts – it’s about fiscal responsibility and environmental stewardship. Building infrastructure based on phantom traffic growth risks saddling the region with excessive debt for oversized facilities we don’t need, while potentially causing unnecessary environmental damage. The Purpose and Need statement’s exaggerated growth projections are being used to justify a massive project when more modest alternatives might better serve the region’s actual needs.

The implications are serious. If the Purpose and Need statement artificially eliminates reasonable alternatives from consideration by overstating future traffic growth, the entire environmental review process is legally suspect. Courts have consistently held that agencies cannot define project purposes so narrowly that they eliminate reasonable alternatives from consideration. The Ninth Circuit Court of Appeals, which covers Oregon and Washington, has explicitly stated that “an agency cannot define its objectives in unreasonably narrow terms.”  But that’s exactly what the IBR project has done:  called for a project that accommodates 1.5 percent annual traffic growth, even though traffic is growing one-fifth as fast.

The solution is straightforward: update the Purpose and Need statement to reflect actual traffic trends and realistic projections. This would allow for consideration of a broader range of alternatives, potentially including more modest solutions that might better match the region’s real needs while reducing environmental impacts and costs. Instead of being locked into a massive project designed for phantom traffic, the region could explore solutions scaled to actual demand.

The Interstate Bridge Replacement project is potentially the region’s largest-ever infrastructure investment. Getting it right matters. But you can’t get the right answer if you start with the wrong question. By clinging to demonstrably incorrect traffic projections in its Purpose and Need statement, the project risks building tomorrow’s infrastructure based on yesterday’s flawed assumptions. Before proceeding further, project leaders should revise their Purpose and Need statement to reflect reality, not highway engineer fantasy.

The Interstate Bridge Project’s traffic projections pretend that the massive shift to “work-from-home” never happened

The IBR traffic projections rely almost entirely on pre-Covid-pandemic data, and ignore the dramatic change in travel patterns.

Traffic on  I-5 is still 7 percent below pre-pandemic levels, according to Oregon DOT data

Traffic on the I-5 bridge is lower today that the purported 2005 baseline for the Columbia River Crossing project (135,000 vehicles per day).

Post-covid travel analyses have shown a permanent shift toward lower growth in vehicle miles traveled.

It’s a violation of NEPA to ignore scientific evidence that travel patterns have shifted and spend $7.5 billion on a project for a world that no longer exists.

The Interstate Bridge Replacement project’s traffic and revenue forecasts appear to be built on increasingly shaky ground. New data from multiple transportation agencies shows that post-pandemic travel patterns have dramatically diverged from pre-pandemic trends, calling into question the fundamental assumptions underlying the multi-billion dollar project.  Traffic is now lower, and growing more slowly than prior to the pandemic, contrary to the assumptions built into IBR traffic projections.

The Covid Pandemic and work-from-home fundamentally changed traffic patterns, and there’s no evidence that growth has reverted to even its very weak, pre-pandemic trend.  ODOT statistics show bridge traffic in 2023 was no higher than in 2015.

Recent analyses from both Oregon and Washington state transportation departments reveal that systemwide traffic volumes have not only failed to return to pre-pandemic levels but show signs of a persistent structural shift in travel behavior. The Oregon Department of Transportation reports that I-5 traffic in Portland remains 7 percent below 2019 levels in 2023 – an even larger decline than the 6 percent reduction observed two years earlier. This suggests that rather than recovering, the post-pandemic traffic reduction is becoming more pronounced over time. A 2023 report, authored by ODOT traffic counting expert Becky Knudsen reports that traffic volumes on I-5 are lower now than in 2019, and have not increased following the 2020 Covid-19 pandemic.  

Becky Knudsen, “Pandemic Impacts on Future Transportation Planning: Implications for Long Range Travel Forecasts”, ODOT, July 2023.  

The picture in Washington State is even more striking. WSDOT’s mobility dashboard shows that congestion-related delays on Clark County’s three main roadways have plummeted by over 75 percent compared to pre-Covid levels. This dramatic reduction in congestion suggests that the “traffic crisis” used to justify the massive bridge project may be largely resolving itself through changed travel patterns.

The Interstate Bridge Replacement project’s own data confirms this trend. Their Level 2 analysis reveals that average weekday traffic in October 2022 was still 4.8 percent below 2019 levels, with just 136,500 daily crossings compared to 143,400 before the pandemic. At the historical pre-pandemic growth rate of 0.3% per year, it would take until 2039 – a full 15 years after the projected bridge opening – just to return to 2019 traffic levels.

These local trends reflect broader national shifts in travel behavior. The Federal Highway Administration has dramatically scaled back its projections for future driving growth. While their 2019 forecast predicted light vehicle travel would grow by 1.1 percent annually over 20 years, their 2023 update slashed that projection nearly in half to just 0.6 percent per year. This reduced growth trajectory acknowledges the pandemic’s acceleration of trends like remote work and e-commerce that have fundamentally altered travel patterns.

Research from other states reinforces these findings. The Maryland Department of Transportation estimates that pandemic-induced behavioral changes have permanently changed driving trends.  They conclude:

VMT under all scenarios is estimated to be less than VMT under “Old normal” (Pre-pandemic conditions) scenario. It is estimated that 2045 total VMT reduction because of COVID-19 ranges between 3 % and 12 % with an average of 7 % across all scenarios. 

Shemer, L., Shayanfar, E., Avner, J., Miquel, R., Mishra, S., & Radovic, M. (2022). COVID-19 impacts on mobility and travel demand. Case studies on transport policy, 10(4), 2519–2529. https://doi.org/10.1016/j.cstp.2022.11.011

Even Stantec, the consulting firm preparing traffic and revenue forecasts for the Interstate Bridge project, acknowledges these risks. Their Level 2 report—not included in the DSEIS— explicitly warns that “potential risks and uncertainties may be magnified by the transitory or permanent effects of the COVID-19 pandemic on mobility, travel, and the economy.”

Yet despite this warning, the IBR project continues to rely on pre-pandemic assumptions that appear increasingly divorced from reality. The Draft Supplemental Environmental Impact statement makes a vague claim that traffic levels are “similar” to pre-covid levels, and claims that it is following “industry standard” practices to simply ignore everything that happened after 2019:

Transportation analyses generally incorporate the most recently available data. However, due to the influence of the COVID-19 pandemic on travel patterns between 2020 and 2023 as explained above, the most recently available data is not representative of standard conditions. Therefore, the IBR Program is following industry standards and using 2019 as the baseline year for the existing conditions instead since it most closely resembles standard conditions.
DSEIS, Transportation Technical Report, page 3-2.

The DSEIS also claims that it can continue to rely on the pre-covid Metro “Kate” travel demand model, even though this model doesn’t incorporate any post-2019 data, and also over-predicts current traffic levels on I-5 by nearly 20 percent.  The DSEIS offers no documentation regarding “industry standards” or explanation for why it simply ignored work-from-home and the impact of the Covid pandemic on travel patterns, and its own data.

This disconnect between projections and reality has serious implications. If traffic volumes remain substantially below forecast levels, toll revenues will fall short of expectations, potentially leaving taxpayers on the hook for billions in additional costs. The project’s financial plans assume robust traffic growth to generate toll revenues needed to repay construction bonds. But if post-pandemic travel patterns persist, those revenue projections will prove wildly optimistic.

Before committing billions in public funds to a massive infrastructure project predicated on continued traffic growth, project leaders need to squarely address this new reality. The evidence increasingly suggests we’re not experiencing a temporary pandemic dip, but rather a fundamental shift in how people travel. Proceeding with plans based on outdated pre-pandemic assumptions risks building – and paying for – infrastructure sized for a future that may never materialize.

A prudent approach would be to pause and reassess the project’s scope and assumptions in light of these documented changes in travel patterns. The pandemic has given us an unexpected opportunity to rethink our transportation needs. We should take advantage of this moment to ensure our infrastructure investments align with actual trends rather than outdated projections.

Highway department’s are selling multi-billion dollar highway widening projects based on flawed traffic projections.

The projections prepared for the predecessor of the proposed $7.5 billion Interstate Bridge Replacement project predicted traffic would grow 1.3 percent per year after 2005.  In reality, traffic across the I-5 bridges has increased by only about 0.1 percent per year since then (and at its pre-Covid peak, had increased only 0.3 percent per year).

Actual I-5 traffic levels are more than 30,000 vehicles per day below the levels forecast for 2024 in the Columbia River Crossing EIS.  Rather than increasing by 30,000 vehicles, I-5 weekday traffic has only increased by 3,000 vehicles in 18 years.

Inaccurate and biased traffic models are a misleading and even fraudulent basis for multi-billion dollar spending decisions.

Claims that we need widen I-5 between Portland and Vancouver are based on projections from traffic models. The best evidence of how well a traffic model works is how accurate its predictions have been.  By that standard, we already know that the traffic models developed for the Interstate Bridge Project are simply wrong and untrustworthy.

We know because we’ve run that experiment.  In 2008, the Oregon and Washington highway departments released an Environmental Impact Statement for the same project—then called the Columbia River Crossing—claiming that if nothing was done—the so-called “No-Build” scenario—traffic on the I-5 bridges between Portland and Vancouver would grow at an annual rate of 1.3 percent per year for the next twenty five years.

Now, more a decade and a half later, we have the actual lived experience to see how accurate this forecast was.  The following chart shows the CRC “No-Build” forecast (in red) and actual weekday traffic levels (in blue) as reported by ODOT’s traffic-counting website.  It’s obvious that the traffic modeling for the CRC was wildly exaggerated.  The model claimed that traffic was going to grow by now to about 170,000 vehicles per weekday—an increase of 35,000 from 2005 levels.  In reality, weekday traffic on the I-5 bridges is now just 136,000.  Instead of growing at a predicted 1.3 percent per year, traffic growth averaged just 0.1 percent per year from 2005 to 2023.

We’re now 18 years—almost three-quarters of the way—through the 25-year period covered by the earlier traffic projections.   A failure this large is strong evidence that no one should trust the highway department’s modeling of future traffic levels:  Their own history shows they’re guilty of error and exaggeration, problems that they have neither admitted nor fixed.

What this demonstrates is that these highway department models aren’t accurate, and that they are biased.  They don’t accurately predict growth rates, but the errors aren’t random—the models consistently exaggerate future growth, which neatly fits the agenda of the highway departments who are trying to sell the public on the “need” for these projects.  Arguably, these intentionally exaggerated over-estimates constitute a fraud against the federal government, which is being asked to fund a much larger than justified project, based on demonstrably false claims about future traffic growth.

Indeed, there was a temporary dip in travel during the pandemic.  But the models were wildly wrong even before Covid.  Between 2005 and 2019 (the last pre-Covid year), traffic grew at a paltry 0.3 percent annual rate—less than one-fourth as fast as predicted by the highway department models. We’ve had roughly three years to recover from the lock-downs and reduced travel of the pandemic, and travel levels still have not rebounded to pre-Covid levels.  That suggests that these models, which simplistically assume ever-upward growth in travel are simply wrong.

One other note:  sharp-eyed readers will see that the CRC traffic estimate for 2005 (135,000) is higher than ODOT traffic counts for that same year (132,600).  The reason is CRC “rounded up” the figure—traffic actually never reached 135,000 until 2015.  ODOT traffic count data report that weekday traffic was 132,600 in 2005 and 135,600 in 2023, in increase of 3000 vehicles over 18 years.  Over a period where models claimed traffic would increase by 30,000 vehicles, they increased by barely a tenth as much:  3,000 vehicles.

What City Observatory Did This Week

What City Observatory Did This Week

There’s a critical flaw in the planning of the $7.5 billion Interstate Bridge project: Metro’s Kate travel demand model is wildly inflating I-5 traffic numbers. The model claims 164,050 vehicles crossed the I-5 bridges daily in 2019, but ODOT’s own traffic counters tell a drastically different story – only 138,780 vehicles actually used the bridge.  Yet IBR is planning starts with this exaggerated level of traffic.

This isn’t just a minor statistical error. Metro’s model has conjured up 25,000 phantom vehicles – an 18% overstatement  – that raises alarming questions about the entire project’s justification. How can taxpayers trust this same flawed model to predict future traffic patterns when it can’t even accurately count current vehicles?  This inflated data also appears to violate federal law. The National Environmental Policy Act demands scientifically sound data for environmental impact statements. By using these phantom vehicles to justify the project’s size and urgency, planners are designing a $7.5 billion solution to an artificially inflated problem.

Interstate Bridge Replacement traffic modeling violates professional and federal standards.  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.

Cooking the Books:  How the IBR used “post-processing” to manually alter Metro travel forecasts to help sell the $7.5 billion Interstate Bridge project.