The San Jose, California; New York and San Francisco metro areas reign supreme on a new index ranking cities by the impact of local transportation on greenhouse gas emissions.

Why it matters: Cities nationwide are trying to preserve the pandemic-era drop in vehicle emissions as traffic returns nearly or entirely to pre-COVID levels.

How it works: The Transportation Climate Impact Index, created by transportation intelligence firm StreetLight Data, ranks cities by a variety of transportation-related emissions factors.

• They include overall vehicle miles traveled (VMT), vehicle fuel efficiency, EV penetration, transit ridership, cycling, walking, truck miles traveled and VMT change over time.
• StreetLight's team ranked the 100 most populous U.S. metros based 0n each factor individually, then created a weighting system to rank cities based on the overall climate impact from transportation.
• VMT carried the most weight, followed by vehicles' fuel economy and transit ridership.

Zoom in: The San Jose metro ranked highest in several categories, including VMT, fuel economy and EV penetration.

• But New York took the lead in transit ridership and bicycle use.
• Orlando, meanwhile, came in first for pedestrian activity, while Baltimore had the biggest decrease in overall VMT.

Yes, but: San Jose's VMT is "coming back fast," StreetLight finds, "a warning sign as [it] looks to lower emissions further."

Losers: The Augusta, Georgia; Omaha, Nebraska; and Columbia, South Carolina metros sit at the bottom of StreetLight's overall ranking.

• Augusta suffers from relatively high miles driven and low use of EVs, fuel-efficient vehicles and alternative modes of transportation, the report notes.

The bottom line: StreetLight reports seeing "signs of progress in many cities throughout the U.S., whether increasing bike lanes to improve connectivity, or improving congestion without adding lanes, or laying the groundwork for robust EV-charging networks."