Westphalia Presidential Parkway, 2021.  Image by the author.

Building over 1,000 miles of new highway and arterial lanes will help the Washington region meet its urgent 2030 greenhouse gas reduction target, according to several Virginia and Maryland transportation agencies and governments — despite decades of research showing the opposite. This was the justification they gave in 2021 when required to explain how their road widening projects for the region’s long-range plan would help us avoid climate catastrophe.

Importantly, this spring, these officials will again have to submit and justify their projects for a special update to the Visualize 2050 regional transportation plan, which explicitly aims to make faster progress on the region’s climate and other transportation goals.

Road widening typically results in more driving and more emissions, a synthesis of the literature shows. While reducing traffic congestion can lower a car’s tailpipe pollution per mile driven, expanding highways and roads generally induces more people to drive more miles, which offsets those emissions benefits and worsens the problem in the long run.

Yet here is how local and state agencies justified their road widening projects:

Jurisdiction / Agency Example answers given as to how highway/arterial widening projects are expected to contribute to reductions in greenhouse gas emissions by 50% below 2005 levels by 2030
Fairfax County / Virginia Department of Transportation “The project provides additional capacity, which will lead to reduced congestion along the corridor, reducing travel time.”
Prince George’s County / Maryland Department of Transportation “While the project will increase auto capacity, it also will improve level of service (LOS), reducing congestion, idling, and emissions in the corridor.”
Loudoun County, Virginia “The project assumption is that building this project will reduce congested streets and or intersections leading to a reduction in vehicle emissions.”
Prince William County, Virginia “Project alleviates congestion to reduce GHG emissions and includes ped/bike facilities to provide non-motorized transportation options.”
City of Manassas, Virginia “Project will improve operations and reduce congestion to mitigate GHG emissions.”
Frederick County, Maryland “Eliminating the current congestion would reduce emissions on [road name] by creating a more efficient travel situation with flowing vehicular travel leading to reduced commute times.”

Source: TPB, 2021, Visualize 2045 Update, How each sponsor agency indicates the projects advance the TPB policy priorities and federal planning factors

In response to the checkbox certification that the project “would contribute to reductions in emissions of greenhouse gases by 50% below 2005 levels by 2030,” some jurisdictions like Fairfax County checked the box “yes” for nearly every single one of its road expansion projects.

Others, like Loudoun, didn’t check these boxes but still stated that they “assumed” it would reduce emissions. Many jurisdictions sought to make their road expansions look better by noting there would be a sidewalk or trail next to the widened six lanes of high-speed traffic to provide an alternative to driving.

Maryland State Highway 210 by Kristen Jeffers licensed under Creative Commons.

Ignoring induced driving

Aside from the above simplistic emissions reduction claims, the congestion reduction claims also come with a huge asterisk. Studies show that congestion reduction from widening roads is temporary, and often worse in the long-term as metropolitan areas become more auto-dependent. Expanded highways generate more and longer car trips than would have occurred without the additional lanes, typically followed by car-centric land use patterns, and those lanes all fill back up with traffic in five to 10 years.

We’ve known this a long time – even this 1999 Washington Post article described the phenomenon along the widened I-270 in Maryland, and years of GGWash coverage have detailed the same. Unfortunately, many transportation officials still don’t understand induced demand and metro areas continue to repeat history.

The Washington region Climate Change Mitigation Study, which was presented to all of these local agencies, noted that express toll lanes projects that widen highways typically don’t help reduce climate pollution either, because they add more lanes. That study also showed that even with a rapid adoption of electric vehicles, our region has to reduce per capita miles of driving by 20% to meet its climate target. We can’t do that with the $28 billion in road expansion projects in Visualize 2045 — double its funding to improve transit, walking and biking.

Prince William County, Image: COG/TPB, Approved Visualize 2045 Long-Range Transportation Plan, p. 120 (image cropped to fit article format)

The 1,000-plus new lane miles would increase driving by 3 to 4 billion miles per year, the SHIFT Calculator shows. Northern Virginia’s TransAction transportation plan would add even more new lane miles if it could, resulting in residents driving more miles for daily needs.

Last summer, the National Capital Region Transportation Planning Board (TPB), which comprises our local government and state transportation officials’ representatives, adopted a stronger greenhouse gas reduction target for cars and trucks. This means that our local officials and transportation agencies need to do more to shift trips to sustainable and more affordable non-auto travel modes, provide housing in walkable activity centers, and electrify vehicle fleets.

Yet, TPB’s Frequently Asked Questions provided to the public for the Visualize 2050 transportation plan update don’t clarify the issue of induced demand and emissions. The FAQ #6, responding to questions about the agency statements in the table above, omits the fact that road widening generally induces more travel and more emissions, simply stating that:

“Emissions of pollutants, including greenhouse gases, have a complex relationship with vehicles, vehicle occupancy, and the operating conditions of the vehicles. As such, it would be incorrect to generalize that all roadway capacity-adding projects will increase emissions. For example, vehicles operating at low/congested speeds emit higher number of certain pollutants; they also consume more fossil fuel, which results in higher levels of GHG emissions. Improvements to relieve such congested travel can help to reduce emissions.”

McLean Metro station at dusk by Daniel Kelly used with permission.

An opportunity for a better approach

Over the next several months, these agencies will decide on projects to submit for inclusion in the Visualize 2050 regional transportation plan. Will Greater Washington counties, cities, and transportation agencies follow through on their climate and other commitments? Or will they ignore induced demand and repeat past talking points to justify bigger and bigger highways?

The public can weigh in through May 31 on the transportation projects and future it wants for its community and for Greater Washington.

Bill Pugh, AICP CTP, is an urban planner, advocate for a livable planet, and senior policy fellow for the Coalition for Smarter Growth. He lives in Alexandria.