pacific nw transportation consortium region 10 Pactrans

Examining the Effects of King County Metro Carpool Incentive Fund

PI: Qing Shen (UW), qs@uw.edu, ORCID: 0000-0002-0968-7377

Co PIs: none

AMOUNT & MATCH: $45,000 from PacTrans; $45,000 Match

PERFORMANCE PERIOD: 8/16/2018 – 8/15/2020

STATUS: Completed

CATEGORIES: Carpool Incentive Fund, Transit, Alternative Transportation

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DESCRIPTION: The project will examine the outcomes of the CIF program with the ultimate goal to identify effective ways for public transit agencies to promote carpools that generate desirable social and environmental outcomes. The research will aim to answer several questions: 1) Do monetary incentives significantly influence the use of carpooling, particularly with any evidence of mode shift from single occupancy vehicle (SOV) to ridesharing? 2) Do carpool trips show distinctive spatial and temporal patterns? Do they compete with or complement fixed route public transit? 3) Do carpool trips reduce VMT without significantly increasing travel time?

App-based demand-responsive carpooling reduces the time cost and uncertainty for carpooling, which makes this form of shared mobility more appealing. The provision of monetary incentives further reduces the generalized travel cost for this travel option relative to others, which is expected to increase the mode share for carpooling. However, the new participants of carpooling may be drawn from different modes, including SOV, public transit, walk, and bike. Therefore, the overall impact of the CIF program must be assessed based on the analysis of empirical data. Using monthly data submitted by the contracted service providers, the researchers can find out whether the CIF program significantly influences carpooling as a mode choice. Combining with survey data collected from participants, we can quantify mode shifts from SOV and from other travel options. Further, these data will allow the researchers to examine the spatial and temporal patterns of carpool trips, and through GIS overlay with transit routes and demographic and employment maps, to understand whether carpooling competes with fixed route public transit. Moreover, the data will enable the researchers to estimate the resulting changes in travel mode composition as well as travel distances for each motorized mode, which will show whether the CIF program reduces VMT. The findings will help inform Metro as it considers possible adjustment to the CIF program; the findings may also provide useful information for other public transit agencies that are deliberating proposals for similar incentive programs for encouraging app-based demand-responsive carpooling.