Several recent posts have opined the Northgate Link debut this September will demonstrate Sound Transit should have never extended Central Link beyond UW Station. This post details why that demonstration will be dwarfed by Sound Transit's 2023 debut of East Link light rail extension across I-90 Bridge.
The Northgate Link debut will demonstrate light rail routed through the DSTT does not have the capacity for the number of transit riders needed to reduce I-5 travel times into Seattle from Northgate. The East Link debut will demonstrate light rail limited to half the DSTT capacity will increase I-90 Bridge congestion.
Both Sound Transit extensions violated RCW 81.104.100(2)(b) regarding high capacity transit planning.
High-capacity transportation planning shall include a study of options to ensure that an appropriate range of technologies and services are evaluated. The law requires the study of a do-nothing option and a low capital cost option, along with the higher capital options that consider use of different technologies.
Sound Transit never considered reducing congestion on either I-5 or I-90 with additional bus routes into Seattle. A decade ago they could have added DSTT tunnel light rail transit capacity with a hundred bus routes an hour without spending a dime on light rail extensions. And more could have been added as needed.
The Northgate Link adds transit lanes into Seattle and minimizes impact with tunnel. East Link confiscates the I-90 Bridge center roadway and devastates route into Bellevue, ending its persona as the "City in the park". It precluded 2-way BRT on center roadway with 10 times light rail capacity, 10 years sooner, at 1/10th the cost.
Riders added by Northgate Link will reduce access for University Link commuters. East Link operation will halve Central Link capacity beyond International Station, adding to futility of Federal Way extension.
Sound Transit will attempt to make up for their decade long failure to add parking with access to transit by using Northgate Link to replace bus routes into Seattle. However, they'll continue routing ST510 into Seattle during peak commute. Snohomish Community Transit plans to continue routes into Seattle and King County Metro is adding bus routes from Northgate. Thus, I-5 commuters will still have access to bus routes into Seattle.
The East Link debut will end all I-90 bus routes into Seattle. Sound Transit and King County Metro have agreed to halve current routes as part of the "bus intercept" agreement with Mercer Island. The island will be inundated with thousands of commuters forced to transfer to and from light rail. With capacity limited to half DSTT, Mercer Island access during peak commute could be limited. Meanwhile thousands more will lose access to transit, adding to congestion along I-90 corridor into Seattle.
The bottom line is the Northgate Link debut will demonstrate the futility of extending light rail routed through the DSTT beyond Northgate to Lynnwood and beyond Angel lake to Federal Way. If Sound Transit ignores that result, the 2023 East Link debut will demonstrate the subsequent $5 billion spent on extensions will dwarf that debacle.