SamTrans Dumbarton Corridor Study and the opportunity for car trip reduction

Analysis of data in the SamTrans Dumbarton Corridor study suggests significant opportunities to reduce vehicle trips and address congestion with transportation demand management. But the study itself does not consider this major opportunity.

The study reports that currently, public and private buses carry  represent 2-3% share of person-trips across the bridge.   SamTrans predicts that the transit improvements proposed in the study would “achieve a target transit mode share across the Dumbarton Corridor of 30 percent by 2040 (20 percent by 2025).” (5-3)

But meanwhile, according to recent data, Stanford University sees about 50% mode share from commuters traveling over the bridge today, with about 40% transit mode share and 10% rideshare from Alameda County.  Today.


To achieve these results, Stanford gives out transit passes, supports carpooling, provides a guaranteed ride home service for people who have unexpected needs to get home when buses aren’t running, helps commuters with first-mile solutions to get to the buses, and provides carshare options for people who need to run errands during the day.  And last but not at all least, Standford charges for parking, so commuters have a financial incentive to avoid driving if they can.

Using data in the Dumbarton report, analysis suggests that the top West Bay job destinations account for about two thirds of peak-direction commuting (from Table 4.2).   Menlo Park and Palo Alto alone appear to account for 30% of those peak trips.

All of these destination cities (Redwood City, Menlo Park, Palo Alto, Stanford, Mountain View, Sunnyvale) have transportation demand management strategies at different stages of implementation.  
The Dumbarton Corridor study itself acknowledges the power of effective transportation demand management, since the projections were adjusted “Incorporating actual mode shares in cases where they are monitored and enforced, including trip caps applied to Stanford, Facebook, and the North Bayshore area of Mountain View.”

But the Dumbarton study does not consider opportunities to craft and strengthen TDM programs to reduce solo driving across the bridge.  If Palo Alto and Menlo Park partnered on TDM, the partnership could greatly relieve traffic congestion and cut-through traffic on Willow and University.

If SamTrans extended service to Redwood City, Mountain View and Sunnyvale as proposed, and these cities also strengthened their transportation demand management programs with a focus on transbay commuters, we would see many fewer cars crossing the bridge, potentially making a significant difference in congestion.

Draft guidelines for the new SB1 Congested Corridors funding program favors investment in transportation demand management. And the new draft State Rail Plan encourages and supports transportation demand management along corridors that are getting rail and bus investments.

Strategies for corridor transportation demand management are about to become mainstream recommendations, and criteria for state funding. This makes sense because TDM programs providing incentives for transit and high-occupancy modes help deliver the best results in person-throughput, reduced congestion, and improved mobility.