I recently returned from
several days in the Washington DC area as part of my goal to visit all of the
world’s major western art museums. The National Gallery of Art and the
Smithsonian Museum along with the National Air and Space Museum, White House, Capital, Library of Congress and
other museums were welcome additions to my ”bucket list”. It also
provided the opportunity to sample the Washington DC Metro system and the 6
separate lines that accommodate nearly 800,000 daily riders. Each
train consists of up to eight 190-seat cars with additional room for those
willing to stand. Each line has more than 6 stations that can
accommodate the 8-car trains in DC for riders to egress and access Metro.
Compare that with Sound
Transit’s Central Link capacity through the Downtown Seattle Transit Tunnel
(DSTT). The DSTT station length limits Central Link trains to four
74-seat cars. The PSRC concluded safe operation required a minimum
of 4 minutes between trains and that each car can accommodate up to 148 riders,
or 8880 riders per hour in each direction.
However, since most of
the Central Link riders will use the two DSTT stations for egress and access,
even this limited capacity requires they accommodate nearly 150 riders a minute
on each side of the two stations.
It’s not clear how the arriving riders will be split between the two stations. A
5.5 wide stair can accommodate 30 ppm, escalators 90 ppm, so assuming up to 90
will chose either station, 16.5 ft wide stairs or escalator will
be required at each station to accommodate riders arriving at the stations.
Departures are even more "problematic". Each person standing
takes up ~7 sq. ft. so it’s not clear whether the two relatively small
DSTT stations can accommodate all those waiting on the platform for trains. Especially since an unknown number of commuters per hour will be choosing to use each station for the return commute. With
4 minutes between trains, large numbers of commuters will be attempting to wait at platforms for
access to Central Link north.
Central Link south to
Federal Way and East Link commuters will have to wait for 8 minutes between
trains at each station. In this case not only is it unclear how many
will use each station, but which train they need to access. Thus the
number of commuters at the two station platforms needing access to the right train
is even more "problematic". Again it’s "doubtful" the stations will provide
platform space for those waiting for access to their trains.
All of these
concerns reflect the PSRC estimate the DSTT limited capacity to 8880 riders per
hour. Sound Transit’s claim the DSTT can accommodate up to 16,000
riders per hour in each direction nearly doubles the problem with access to
stations and platform space for access to trains.
All the station concerns apply to initial Central Link operation. The
money spent on Prop 1 extensions along I-5 north of the UW station and south of
SeaTac and across I-90 Bridge through Bellevue to Redmond do nothing to
increase light rail spine or DSTT station capacity. Riders added by the extensions
will only reduce access into Seattle for existing Central Link riders and numbers waiting at stations for return trips. The riders
added by the billions spent on the ST3 spine further reduce their access into Seattle and increase number of those needing platform space for return trip.
The bottom line is DC
Metro provides a transit system with 6 lines, each with up to eight 190-seat
car trains routed to six or more light rail stations in the city. Sound Transit's light rail spine capacity and its egress and access in Seattle, are limited by two stations in the DSTT to four 74-seat cars, a fractions of what's required to reduce congestion on any transportation corridor. It's bad enough they're spending billions on "Prop 1 and Beyond" extensions attempting to reduce congestion along the I-5 corridor from Everett. It's absurd they're attempting to use its limited capacity to do so on both south I-5 and I-90 corridors.
It’s way past time for
Sound Transit and the Seattle Times Traffic Lab to recognize why DC Metro works
and why Prop 1 won't.
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