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Want to Lower Your City’s Transportation Emissions? Drive Less

Reducing vehicle miles is the most powerful way to cut greenhouse gas emissions, an executive at StreetLight Data said. Its new 2024 U.S. Transportation Climate Impact Index ranks the nation’s 100 most populous metropolitan areas.

Lines of cars stopped in traffic going away from the camera.
Reducing transportation-related greenhouse gases requires a multipronged approach, a mobility analytics executive said recently, after its new annual report analyzing emissions in the nation’s 100 largest cities found a majority of heroes and offenders in California and the South.

Released March 14, StreetLight Data’s 2024 U.S. Transportation Climate Impact Index analyzes the transportation-related greenhouse gases of the 100 most populous cities. The firm’s work centers on mobility data analytics.

The top five performing metropolitan areas were San Jose, Calif.; New York City; San Francisco; Los Angeles; and Seattle. The five worst performing metros were Bakersfield, Calif.; Jackson, Miss.; Columbia, S.C.; Omaha, Neb.; and Augusta, Ga.

When looking at vehicle miles traveled (VMT), Augusta, Bakersfield and Omaha rounded out the Nos. 98, 99 and 100 ranks, respectively, according to the report. The top three regions where VMT per capita was lowest were San Jose, Seattle and Detroit, which ranked Nos. 1, 2 and 3, respectively. Improving those numbers, said StreetLight’s Director of Content Emily Adler, will require a multifaceted approach driven by policy and programs to reduce the miles driven, transition away from fossil fuels and make public transit and other modes more attractive.

“Yes, reducing vehicle miles traveled is the most powerful tool to reduce emissions,” Adler said. But other means are competitive: “Improving transit, biking and walking, and land use planning are some of the most effective means of reducing VMT because they give people an alternative means of low- or no-emissions travel and proximity of services.” Incentivizing EVs and building out EV infrastructure are other powerful ways to reduce emissions, she said, cautioning that emissions sources will vary by locality.

The Climate Impact Index evaluated transportation across eight factors: VMT, electric vehicle adoption, transit ridership, bicycle activity, pedestrian activity, fuel economy, truck miles traveled and percent change in VMT from June 2022 to May 2023. Transportation is considered the largest single-sector contributor to greenhouse gas emissions.

But not all categories were weighted the same. For example, not all vehicle miles driven carry the same level of greenhouse gas emissions. Electric vehicle penetration and the fuel economy of cars can help to lessen the effects of heavy driving activity. Generally, however, policies and programs to reduce VMT — and the political will to implement them — can improve a city’s ranking on the climate impact scale.

There are many factors that can affect VMT, which is where policy and programs come into play. San Jose is so focused on reducing greenhouse gases across the board, officials have been developing a future that includes sustainable energy storage systems — also known as microgrids — as well as managing their solar portfolio.

“We’re specifically trying to build microgrids and battery energy storage for our 130 critical facilities,” Carol Boland Whattham, program manager for sustainability and microgrids in San Jose, said during a panel at the Smart Cities Connect Conference and Expo in October, in the Washington, D.C., region.

It is this kind of public policy, to address carbon emissions on a variety of fronts, that helps contribute to a region’s improved ranking. These policies help to round out an overall dedication to addressing climate change, but can also address more on-the-ground societal challenges like transportation equity.

Dev Wakeley, worker policy advocate for Alabama Arise, a statewide organization advocating for policies around transportation, poverty and other areas, pointed out Alabama is one of a few states in the nation that does not fund public transit at the state level.

Birmingham, Alabama’s largest city and metro region, has an overall ranking on the Climate Impact Index of 90 out of 100. The city ranks 86th in transit ridership, and dead last in both pedestrian activity and cycling.

“The persistent pattern of disinvestment has been something we’ve had to overcome in a lot of ways in the state, not just in transit, but in pretty much every quality-of-life measure,” Wakeley said. “So, we have to make the case to remedy that, in transit, and in a lot of other different areas of state spending and investment.”

The case for more state funding has been heard in other parts of the transit universe, as public transit emerges from the effects of the COVID-19 pandemic.

“Transit in almost every part of the United States is insufficient,” Yonah Freemark, one of the authors of the Urban Institute report Surmounting the Fiscal Cliff, said during a November webinar on the report. “We have to fight, as a community, for better options throughout the country. But at the same time, we also need to develop those new funding sources.
Skip Descant writes about smart cities, the Internet of Things, transportation and other areas. He spent more than 12 years reporting for daily newspapers in Mississippi, Arkansas, Louisiana and California. He lives in downtown Yreka, Calif.