New calculator shows how highway expansions increase traffic


The SHIFT Calculator provides transparency about new traffic created by highway widening and expansion so transportation agencies can make smarter, more sustainable transportation investments.

A new tool released today provides anyone with the ability to estimate the increased traffic and pollution that will result from proposed highway expansions.

Over the past few decades, taxpayer dollars have funded billions of dollars in highway expansions intended to alleviate road congestion, but it usually does not take long for the traffic to return. This endless loop, known as “induced demand,” fails to address congestion while leading to more cars on the road and more pollution from the transportation sector, which is the nation’s largest source of emissions.

Using the State Highway Induced Frequency of Travel (SHIFT) Calculator developed by RMI, NRDC (Natural Resources Defense Council) and Transportation for America, anyone can now project the increases in driving that would result from highway expansions. The Calculator provides transparency and accountability for transportation projects that often do not deliver on promised benefits and instead make traffic and pollution worse. This new tool will enable transportation agencies to account for the principle of induced demand in the planning and implementation of highway projects.

“Road expansion projects have failed to deliver the promised benefits. In fact, the evidence shows that they actually make traffic and pollution worse,” said Ben Holland, manager in RMI’s Urban Transformation Program. “To achieve US climate goals, we must reduce the amount that the average person drives by 20%. This tool shines a light on the impacts of highway expansion and shows how these projects often move us away from our goals.”

The SHIFT Calculator was based on RMI’s Colorado Induced Travel Calculator, which advocates used to show that proposed and in-progress road expansions would increase vehicle miles traveled by up to 3% by 2030, at a time that the state is aiming to reduce those roadway miles by 10%.

“This easy-to-use tool will help advocates make their case to city and state transportation departments,” said Carter Rubin, a transportation strategist at NRDC. “So many of us have seen firsthand how quickly traffic returns when extra highway lanes open up, and this calculator provides the numbers to back up that experience. If cities and states really want to get residents out of traffic and cut down on smog, they should make it easier and faster for people to ride public transit, bike and walk.”

“For 90 years, we have known that building new lanes creates new vehicle trips that fill those lanes, and for 90 years, we have mostly ignored this fundamental law while repeating the same mistakes at great cost,” said Beth Osborne, director of Transportation for America. “We must stop making empty promises about congestion reduction that never materialize. Having the ability to estimate added travel caused by expansions can finally equip decision makers and the public with the data to make the case for something more effective at connecting people to jobs and opportunity.”


About RMI

RMI is an independent nonprofit founded in 1982 that transforms global energy systems through market-driven solutions to align with a 1.5°C future and secure a clean, prosperous, zero-carbon future for all. We work in the world’s most critical geographies and engage businesses, policymakers, communities, and NGOs to identify and scale energy system interventions that will cut greenhouse gas emissions at least 50 percent by 2030. RMI has offices in Basalt and Boulder, Colorado; New York City; Oakland, California; Washington, D.C.; and Beijing.
More information on RMI can be found at or follow us on Twitter @RockyMtnInst.

About NRDC

NRDC (Natural Resources Defense Council) is an international nonprofit environmental organization with more than 3 million members and online activists. Since 1970, our lawyers, scientists, and other environmental specialists have worked to protect the world’s natural resources, public health, and the environment. NRDC has offices in New York City, Washington, D.C., Los Angeles, San Francisco, Chicago, Bozeman, MT, and Beijing. Visit us at and follow us on Twitter @NRDC.

About Transportation for America

Transportation for America, a program of Smart Growth America, is an advocacy organization made up of local, regional and state leaders who envision a transportation system that safely, affordably and conveniently connects people of all means and ability to jobs, services, and opportunity through multiple modes of travel. Learn more at and follow us on Twitter @T4America.

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