Measuring the impacts of new development


The Grantville Trolley Station in San Diego, CA. (Photo credit: Sam Hodgson, Voice of San Diego)

The largest share of emissions in California and the country now come from the transportation sector. To address the emissions, the City of San Diego recently developed a tool to help planners determine where and what kind of development should occur to reduce single occupant vehicle use and vehicle miles traveled (VMT) — two key contributors to overall transportation emissions.

The tool is part of San Diego’s ambitious Climate Action Plan to reduce the city’s greenhouse gas emissions by 50 percent by 2035. The tool helps planners determine whether development proposals comply with the Climate Action Plan, and provides a numeric range of target housing density and employment intensity that a community should achieve to reduce VMT.

Notably, the tool will not require new development proposals to meet the Climate Action Plan’s transit and bike usage targets, and focus instead on VMT reduction. The change comes after the city’s latest proposed developments failed to reach transit usage goals, but did reduce VMT. The city makes the case that focusing on VMT “makes more sense because it is a more direct measure for greenhouse gas reductions” and better accounts for technological impacts of ridehailing services and automated vehicles.

Still, some advocates raised concerns that eliminating transit, walking, and biking targets as a required consideration for new developments will weaken support for transit, bike, and pedestrian infrastructure expansion. Furthermore, disagreements about how to measure projected VMT resulted in a public squabble over a major proposed redevelopment of a former stadium site. SoccerCity is envisioned to become a dense mix of housing, office, and retail space on a major trolley stop in the middle of the city. Yet a study released this week found that SoccerCity would generate more traffic than its developers promised, undermining the city’s vision.

Though San Diego’s Climate Action Plan is certainly commendable, these drawbacks and disagreements show how hard it is to support sustainable transportation on policy alone, and how the right tools are needed to measure the impacts of new and proposed development. For resources on ways to measure TOD and vehicle trips generation rates, access Effects of TOD on Housing, Parking, and Travel, a report by the Transit Cooperative Research Program featured in the library.

Recent TOD news

Here are a few things that have been happening this week with TOD projects across the country.

  • What are transit-oriented development districts and how can they help Nashville (Tennesseean)
  • Google’s future home near a growing transit hub seeks to revitalize downtown San Jose (Curbed)
  • Five corridors examined for development, transit in Columbus (Columbus Dispatch)
  • How Elon Musk’s proposed tunnels under Los Angeles would impact development (Governing)