GreenTRIP Research

Helping identify the benefits of different traffic reduction strategies.

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About our Research

The focus of our research is to better understand what strategies best reduce traffic and increase affordability for families. The data we collect and collaborate on improves our approach to planning. Plus, it provides city officials, developers and community members with the evidence they need to make a strong case for developments that prioritize people over parking.

GreenTRIP's research, in conjunction with some top institutions, fills a gaping hole in existing data needed to quantify the traffic and vehicle ownership reduction benefits of affordable homes near transit. Empirical research to fill this gap is badly needed. Current transportation models predict that future residents in a development that is dedicated as affordable for low-income residents will drive only 4% less than a market rate development. We believe reductions should be in the range of 30-80%, depending on location. Similarly, we believe that the impact of traffic reduction strategies such as transit passes and carsharing is much greater than current models predict. 

Our research partners include the Center for Neighborhood Technology (CNT), and the California Housing Partnership Corporation (CHPC)

Current Research

Traffic Benefits of Affordable Homes: We helped develop a Caltrans research proposal to study the trip generation benefits of affordable housing and traffic reduction strategies. Once complete, this information will finally give affordable housing, transit passes, and other strategies the credit they are due as traffic and greenhouse gas reducers. TransForm is part of the team, led by Portland State University, chosen to conduct this statewide study, beginning in 2015. View the call for projects and RFP here.

More Traffic Benefits for LA: In Los Angeles, city staff are working on a study collecting traffic data associated with affordable homes. This is funded by a grant from the Strategic Growth Council to plan for infill development. The trip generation data will help the city revise assumptions for affordable homes and for parking demand. TransForm serves on the advisory panel, and plans to integrate LA's data into a Parking Database similar to the one CNT created for TransForm for the Bay Area.

Past Research

Travel Behavior by Income and Transit Proximity: Working with the California Housing Partnership Corporation and CNT, we analyzed the 2013 statewide transportation survey (the CA Household Travel Survey or CHTS), and used the information to better understand the parking and traffic impacts of affordable homes near transit.  Funded by the Ford Foundation, we released a groundbreaking report in 2014 that quantified the greenhouse gas benefits of investing in more affordable homes near transit. The report’s conclusions paved the way for including these strategies as part of the State’s greenhouse gas reduction strategies in the AHSC (Affordable Homes and Sustainable Communities) Program. We are now using that information in GreenTRIP Connect, a predictive travel and emissions model for statewide use.

Transit Pass Use Survey and Implementation: GreenTRIP staff conducted resident surveys of two Mid-Peninsula Housing projects near transit in the City of San Mateo where residents currently receive free transit passes. In April 2015, GreenTRIP identified and shared best practices of transit pass administration and user support with developers in San Mateo County. Read the info sheet here and for the full report, please contact This project was funded through Enterprise Community Partners

About the GreenTRIP Parking Database

Funded as part of the Metropolitan Transportation Commission's Regional Prosperity Plan in 2014, our Parking Database hosts data on actual parking usage at 80 housing developments around the Bay Area. The publicly available database is for city staff and leaders, community groups and housing developers. Stakeholders can use local data and case studies to show how greater affordability, proximity to transit and strategies like those in GreenTRIP certified buildings reduce the need for parking. 

Learn more about the GreenTRIP Parking Database and start using it.

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Get Involved

For more information, contact Ann Cheng.