Weekend Reads | Transportation and Climate Impacts

by Kevin Schofield

This weekend's read is a report by the data analytics firm StreetLight Data looking at the top 100 metro areas in the United States and their transportation systems' greenhouse gas contributions. Transportation is the single largest contributor to greenhouse gas emissions in the United States, accounting for 28% of all greenhouse gas emissions in 2022 (followed by electric power generation at 25% and industry at 23%). It follows, then, that any substantial reduction in greenhouse gas will need to involve "greening" our transportation system.

StreetLight built a "transportation climate index" ranking, using eight factors:

• Vehicle miles driven annually
• Fuel economy
• Transit ridership
• Electric vehicle penetration
• Bicycle activity
• Pedestrian activity
• Truck miles traveled annually
• The change in vehicle miles traveled compared with the prior year

It weighted each of these factors based on its relative climate impact. Not surprisingly, vehicle miles traveled had the highest impact, almost double that for the next-lowest, fuel economy.

Among the general trends, it found that cities on the coasts and in the Northeast led the rankings — especially those with high rates of remote work, which has kept vehicle miles traveled low. In a similar vein, cities up and down the West Coast that have led the way in adoption of high-fuel-economy cars and electric vehicles (EVs) also rose to the top of the rankings. StreetLight does point out, however, that EV penetration is still very low, and that it correlates with a metro area's wealth.

StreetLight also noted that there has been a "biking boom" in the past few years, though at the same time, pedestrian activity has dropped. And it calls out that after a significant drop in vehicle miles traveled during the pandemic that persisted for a while due to new remote-work habits, many cities are now seeing a dramatic rise. In fact, the San Jose metro area, despite being ranked No. 1 overall for transportation climate impact, is now in the bottom third for change in vehicle miles traveled.

The Seattle metro area, including Tacoma and Bellevue, ranked No. 5 overall in the index. We scored well on low vehicle miles traveled (we have plenty of remote workers here), on fuel economy and EV penetration, and on transit (No. 5) and biking activity. Not so much, however, on pedestrian activity, and we ranked way down the list at No. 62 on recent change in vehicle miles traveled as those remote workers head back to the office.

On the other side of the state, Spokane did surprisingly well given its rural surroundings, coming in at No. 35 nationally. It did poorly on fuel economy (No. 99) and EV penetration, and also poorly (like Seattle) on pedestrian activity, but well on vehicle miles traveled — and near the top of the list in its recent change in miles traveled. The city scored reasonably high on transit ridership and biking activity, things we rarely associate with Spokane.

The cities with the worst scores tend to cluster in the Midwest and Deep South, with a couple of notable surprises: Detroit, the "motor city," came in at No. 23; and Minneapolis, known for its progressive politics, was ranked No. 75. In both cases, it came down to vehicle miles traveled, where Detroit was No. 3 nationwide and Minneapolis was No. 89, barely squeaking out of the bottom 10.

It will be interesting to see how the rankings change in the coming years. As EV penetration grows and the cost of EVs drops, we might expect that fuel economy and EV penetration will ultimately have more impact on greenhouse gas emissions than total vehicle miles traveled. That will depend, however, on the extent to which we can "green" electric power generation: remember that 25% of the nation's greenhouse gas emissions come from power generation. If we can't move to more sustainable sources, such as solar and wind, then in the larger ecosystem, we won't be dramatically reducing the climate impact of vehicle miles traveled; we will simply be moving the emissions from the car engine to the power-generation plants.

2024 U.S. Transportation Climate Impact Index

Featured image via l i g h t p o e t/Shutterstock.com.