Yesterday SDOT released the executive summary of a report looking at the impacts of tolling the deep bore tunnel. The report focuses on WSDOT’s SDEIS tolling analysis, highlighting major issues that have yet to be addressed. Regardless of your position on the tunnel, and especially if you support this tunnel and want it to function better for Seattle, this report points out significant issues that WSDOT has yet to address.
Tolling of the tunnel, and the significant resulting diversion is a major outstanding issue that WSDOT has yet to plan for and mitigate adequately. Toll diversion is expected cause 50%-55% of tunnel traffic to divert to surface streets or I-5, which will have a large effect on Downtown’s transportation system and in some ways undermines WSDOT’s rationale for building the tunnel. If the tunnel is built, the best tolling system would be structured to minimize toll diversion and maximize utilization of the tunnel’s capacity.
In a letter that accompanied the report, Peter Hahn, Director of SDOT, accuses WSDOT of canceling Final Environmental Impact Statement (FEIS) comment discussion meetings and not rescheduling them, essentially cutting SDOT out of the process. The letters says that after the cancellation of these meeting, WSDOT informed SDOT that no other comments would be accepted from the city.
A summary of the major points made in the executive summary are below the jump.
- Investments in surface streets, non-motorized modes, transit and transportation demand programs are necessary. Toll diversion will redirect between 40,000 and 48,000 vehicle trips from the tunnel to I-5 and surface streets increasing the need for a well functioning surface street system. Funds for these types of projects are not included and such a high toll diversion rate (50%-55% of tunnel trips) raises the question of whether or not the tunnel is the most cost effective investment.
- Analysis in the Supplemental Draft Environmental Impact Statement (SDEIS) does not include the “Elliott/Western” connector that is being built. This connection will provide an attractive alternative route, parallel to the tolled tunnel, and will increase the rate of diversion beyond that identified by WSDOT.
- Vehicle trips in Seattle are declining despite population and employment growth. Vehicle trips in Seattle has dropped 8% since 2003 and traffic volumes in downtown Seattle have not changed for 10 years.
- The SDEIS does not included travel demand management (TDM) programs. The Partnership Process (stakehold group that looked at multiple options including surface options) identified an aggressive TDM program that removed 15,000 vehicle trips a day from downtown Seattle for a ten-year cost of $57 million. TDM programs are especially important for the viaduct since peak period vehicle volumes are twice as high as mid-day volumes, which can be handled by a four lane arterial.
- Transit service south of Downtown may need additional protection from increased surface street congestion. Construction and operations of Metro’s RapidRide lines is important to reduce vehicle volumes and currently has an uncertain funding outlook.
- Region-wide tolling of the freeway system is highly likely in the future, and will lead to an overall reduction of vehicle demand, particularly during peak periods.
- Highway ramps are the primary cause of congestion on downtown surface streets (see yesterday’s post). The new northern and souther portal areas will see large increases in vehicle volumes because all Downtown bound traffic and diversion traffic must exit before the tunnel.
- The land use model used to generate inputs for the travel demand model does not take into account changes in the transportation network. As our transportation system changes, people adapt their housing and work location decisions to the changing transportation system. The interaction of the two are not accounted for currently.
- The viaduct is important for “light” local goods movement but I-5 is a significantly more important freight corridor on a regional and state level. Investments that reduce congestion on I-5 would overall have a more meaningful impact on freight mobility than the tunnel. Also, freight traffic to the Ballard/Interbay manufacturing and industrial area does not benefit from the tunnel compared to a Surface/Transit/I-5 option.
- The purpose and need statement was revised in the SDEIS to explicitly call for a maintenance of vehicle capacity, not mobility — this is contrast to earlier decisions for the corridor that favored a maintenance of mobility.
Most of these points should not be new to readers of the blog.