By Eric Murphy
Nearly every state DOT is grappling with how to reduce traffic and carbon emissions—many states developed official carbon reduction strategies in 2023, and congestion relief is often at the top of a DOT’s priority list. But a new study from Swedish researchers says that some of the most common ways to address these challenges—using only “carrots” rather than “sticks,” in the researchers’ words—may leave states struggling to achieve their goals.
While most states have official carbon reduction strategies, some states have gone farther and set official targets for emissions reductions in transportation, which require major actions. Some of the strategies DOTs have used to pursue those goals include promoting ways to travel without a car; investment in bus, rail, bike, and walking infrastructure; and even influencing land use and zoning regulations.
Those strategies have their benefits and positive local impacts, but new research finds their impact on reducing traffic and emissions on a large scale might be too limited. In addition to these strategies, DOTs may need to consider others that directly address pricing and road capacity, which could be tougher sells to the public.
Last year, an evaluation of more than 1,500 climate policies published in Science found that two-thirds of transportation policies that successfully reduced emissions had pricing or taxation as at least one element in the policy mix. “In most cases,” the researchers said, “pricing is the complement that enables effective emissions reductions.”
Earlier this year, researchers at UCLA found that despite California’s efforts to invest in infrastructure for biking, walking, and transit and to make more efficient use of land, traffic had remained stubbornly persistent. Limiting road capacity expansions or even reducing capacity, say the researchers, are needed for significant traffic reductions. The Swedish researchers might call this a “stick” solution, in contrast to the “carrots” mentioned above.
They agree with the UCLA researchers that investing in walking, biking, and transit has great local benefits, but by itself hasn’t made enough progress toward cutting traffic and emissions. Because so few people take transit relative to the number of car trips, even doubling the number of transit trips doesn’t put much of a dent in total car traffic.
Mixing land use and increasing density does help people drive less, but not a lot less, according to the researchers. Changes in development patterns happen very slowly, especially in the mature and built–up cities of the U.S. However, say the researchers:
The factors associated with lower car use – density, diverse land use, walkable urban design and so on – are still effective strategies to achieve accessible and livable cities, and to enable equitable access without the need to have a car.
Photo credit: Jacek Dylag on Unsplash. License.