use of the Downtown Seattle Transit Tunnel (DSTT) by Sound Transit for buses
money now budgeted for Central Link light rail to expanding Bus Rapid Transit (BRT)
in the Sound Move Plan.
3. Work to
implement a regional BRT plan that integrates ST Express and Metro bus services,
and that maximizes the use of the DSTT.
Assesment 0f Light Rail or Buses in the Downtown Seattle Transit
Dick Nelson, and Jim MacIsaac
This report was prepared by the
Seattle consulting firm Integrated Transport Research, Inc. in response to an
assignment made in early June 2001 by the King County Council Transportation
Committee to assemble and analyze information that bears on the future use of
the Downtown Seattle Transit Tunnel by Sound Transit's Link Light Rail.
The 1.3 mile Downtown Seattle
Transit Tunnel (DSTT, or simply, the Tunnel) is the centerpiece of the local and
regional King County Metro bus system. Across the entire County, Metro serves
100,000,000 riders per year. The Tunnel lets 25 regional express routes –
producing about a quarter of the rush hour bus traffic in downtown Seattle –
move buses two to three times faster than those on surface streets of the
Central Business District (CBD). The Tunnel served 8,700 riders during the
afternoon peak hour in 1998, with daily boardings of about 23,000.
ITR has concluded that conversion
of the Tunnel to light rail is likely to make downtown Seattle street congestion
in the 2010 to 2020 period much worse than the alternative of simply routing
more buses through the Tunnel. Putting more peak hour buses into the Tunnel in
the near term is recommended by the Link Project Review Committee, the Downtown
Seattle Association, and this study. The Tunnel could support double the current
peak period bus volumes: 300 per hour using the existing buses and route
By examining Metro and Sound
Transit planning documents, we have identified several reasons that downtown
Seattle congestion would worsen with light rail running in the Tunnel:
• Some or all of Metro’s 25
current regional express Tunnel bus routes would be permanently routed onto
downtown streets, with the frequency of these routes increasing over time to
serve more customers.
• Existing local Metro bus
service to downtown Seattle would likely see only a small reduction despite
impressions that light rail will be a substitute service that eliminates many
buses. If customer demand for public transport from locations not served by Link
light rail is to be met in the future, local Metro bus service to downtown would
have to be expanded.
• Expansion would also occur with
non-Metro regional express bus services to downtown Seattle that could
not sensibly be rerouted to be intercepted at light rail stations outside of the
• Joint bus and rail
operations following reopening of the Tunnel would not allow safe
underground passage of enough Tunnel buses to compensate for the previous three
sources of bus growth on the streets of downtown.
Existing planning studies of light
rail from Northgate to South 200th
reveal that rail in the
Tunnel would cause approximately 680 buses to travel in the year 2020 afternoon
peak hour on downtown streets, 48% higher than today’s level of 460 buses. The
number of buses in downtown in 2020 would be even higher if the Link light
rail system were truncated short of Northgate or S 200th. Noteworthy is that
this number of buses on the downtown streets would be higher than the number
achievable with the DSTT remaining an all-bus facility.
Joint bus-rail operation in the
Tunnel adds additional cost and risk with no substantial benefits. The risks
arise primarily from the unprecedented prospect of intermixing buses weighing
66,000 pounds with 600,000 pound trains in a confined space with four or five
station stops. Safety in peak periods will have to be achieved by limiting the
frequency of buses and trains, thus setting a limit on capacity.
Ramping up the number of buses
running through the Tunnel in the afternoon peak hour without interference from
trains offers more and better regional transit service to downtown Seattle at
lower street congestion levels than the alternative of putting Link light rail
in the Tunnel.
Our findings contradict Sound
Transit’s 1994 conclusions that light rail is necessary to supplement bus
service in order to provide sufficient future transit service to downtown
Seattle without congesting streets with a growing number of buses. This
contradiction springs from the fact that the system level alternatives analysis
contained in the 1993 Joint Regional Planning Committee Final Environmental
Impact Statement for regional transit did not provide officials with an
unbiased, realistic comparison between feasible bus/rail and all-bus/transitway
alternatives that provide comparable service levels.
The "fatal flaws" in the
1993 bus/transitway option (specifically, buses facing congestion in the Seattle
CBD, in the University District, and across the Ship Canal) could and should now
be revisited to see if they can be corrected using Sound Transit's funding
sources applied to a stronger bus plan designed by Bus Rapid Transit
Revisiting an updated, expanded
express bus plan is an important option given the fact that an approved,
feasible, and funded light rail plan does not yet exist today, five years into
the ten-year Sound Move Plan passed in 1996. Federal approval of the emerging
light rail starter line will not come until 2002. Sound Transit officials have
admitted that the long-run vision for a light rail system may have to be
truncated at its Phase One terminus points Fortunately, the Federal Transit
Administration is placing new emphasis on Bus Rapid Transit (BRT) as a
lower-cost substitute for light rail. This provides further incentive to examine
the option of implementing an updated BRT system as a total replacement for Link
At the same time, the forecast that
Link light rail (if built) would carry mostly Seattle riders between points
within Seattle underscores the intra-Seattle transit opportunities that could be
filled by monorail, in-city BRT corridors, or other options that are under study
now in the Seattle Intermediate Capacity Transit project and by the Elevated
Summary of Findings
These findings are detailed in the
Finding 1: Operating Link light
rail in the Tunnel would mean that the regional inter-city express bus service
for which the Tunnel was originally built would be replaced with intra-Seattle
light rail service.
Finding 2: If the Tunnel were
converted to rail use either jointly with buses or exclusively, express bus
service quality would decline for suburban riders.
Finding 3: Joint bus-rail operation
in the Tunnel introduces additional costs and operational uncertainties to Metro
over simply converting the Tunnel to exclusive rail.
Finding 4: Joint bus-rail operation
in the Tunnel would introduce additional safety risks over simply converting the
Tunnel to exclusive rail.
Finding 5: Converting the Tunnel to
partial or full light rail use would degrade transit capacity and increase
traffic congestion on downtown streets both during and after the two-year period
Finding 6: Seattle downtown bus
volumes and congestion could be reduced by expanding the volume of buses in the
Tunnel above present levels.
Finding 7: New bus propulsion
technology, combined with a low-floor design, would permit faster loading times
and cause fewer delays than the present buses used in the Tunnel, and thus would
increase its effective bus capacity.
Finding 8: The passenger capacity
of the Tunnel in peak hour conditions is sufficient to carry projected 2020
passenger loads with either buses or light rail trains providing service.
Finding 9: Projections of post-2020
transit ridership based on the growth of employment, commercial services, and
residential population in the Seattle downtown indicate the need for planning
new transit corridor capacity and demand management measures.
Finding 10: Sound Transit's
north-south Link light rail line, if implemented, would offer transit
performance inferior to regional express bus routes on upgraded roadways.
Finding 11: The cost-effectiveness
of an all-bus alternative for regional high-capacity transit in the Puget Sound
region has not yet been compared to a light rail system like the one proposed by
Finding 12: The overall quality of
the Puget Sound regional transit system could be maintained and improved by
retaining the Tunnel for all-bus operations, increasing the numbers of regional
routes using the Tunnel, integrating long- and short-haul routes, and enhancing
the roadway system for congestion free bus travel.
Finding 13: The existing express
bus services of Sound Transit, Metro, Community Transit, and Pierce Transit have
many of the attributes of Bus Rapid Transit (BRT), and could be enhanced to
bring them closer to BRT.
Finding 14: Because Bus Rapid
Transit (BRT) is a new Federal transit mode emphasis, Federal and Sound Transit
funds could be reprogrammed to support an extensive Puget Sound regional BRT
John Niles of Global Telematics served as project
manager for the Tunnel Team. Other members were Dick Nelson, President of ITR,
Inc., and Jim MacIsaac, PE, independent consulting engineer.