Sound Transit’s Floating Bridge/Train Combination's Fatal Flaw

The May 14^th Seattle Times exemplifies the paper's efforts to promote Sound Transit’s flawed “Prop 1 and Beyond” light rail extensions.  In this case they herald their I-90 Bridge design “success” while ignoring the fact it enables an East Link light rail extension that will increase not decrease cross-lake bridge congestion.

  

The front-page article “World’s First: Floating Bridge With a Train” details Sound Transit’s apparently successful design for sections connecting the floating and fixed portions of the bridge that can withstand the loads from trains.  The “floating bridge/train” compatibility issue was first raised 9 years ago by both an independent review team (IRT) commissioned by the legislature and the FHWA.   The purported success in the paper is hardly new.  The Pueblo, Colorado testing described in the article was conducted nearly four years ago during the summer and fall of 2013.  At the time the design was acclaimed as having passed with “flying colors”.   

Apparently it later “crashed” since two years later an August 16, 2015 Times article announced Sound Transit had contracted to spend an additional $20 million completing the design they’d tested at Pueblo and had already spent $36 million on.   Nearly nine months later the problem was apparently still not resolved since the March 2016 Sound Transit board minutes included the following East Link Extension briefing

In the I-90 corridor the system design is at 90% and civil design is advancing to 90%.  The independent review team (IRT) identified 23 issues as part of the preliminary engineering. Twenty-two issues have been closed and the staff is working to close the final issue. 

It wasn’t clear what the “final issue” was in the March briefing.  Presumably the WSDOT affirmation in the article, “light rail will be safe and not wear out the bridge prematurely” reflects the fact it has been resolved.  However, Sound Transit Board member Marchione’s warning “I’m never going to feel 100 percent confident until they get the real train on the real track” seems well founded. 

Especially since the WSDOT in 2005 thought they'd demonstrated I-90 Bridge/light rail compatibility using flat bed trucks to simulate light rail cars. They claimed the “results of the test confirmed previous findings the bridge can be structurally retrofitted to carry the loads associated with the light rail system under consideration, in addition to general traffic on the roadway”.

Assuming floating-bridge/light rail-compatibility success, the paper’s front-page depiction of the I-90 Bridge with East Link trains and Sound Transit buses is a tacit admission of the East Link failure: a lack of capacity.  Sound Transit for years has promoted East Link as the replacement for I-90 Bridge buses.  They claimed 40,000 of the 50,000 riders projected by 2030 would come from terminating all the cross-lake bus routes at either the South Bellevue or Mercer Island light rail stations.  

As recently as the April 2017 East Link SEPA Addendum, Sound Transit’s “Bus Transit Integration Configurations” used East Link to replace essentially all cross-lake buses.  The Sound Transit East Link Extension website video described operation as 3 or 4 car trains every 8 to 10 minutes. The May 14^th depiction showed three-car trains and their April 2017 East Link SEPA Addendum had 8 minutes between trains. 

The decision to show the buses crossing the lake presumably reflects Sound Transit recognition even a four car train every 8 minutes can’t accommodate all the cross-lake transit riders.  That, despite the fact Sound Transit apparently has a bridge design capable of accommodating light rail trains, its operation will not provide the capacity needed to attract the numbers of transit riders required to reduce congestion.   Particularly since any reduction will be on HOV lanes rather than the far more congestion GP lanes.

That requires adding cross-lake bus routes rather than replacing them.  Every 100 additional bus routes can replace 10,000 vehicles not only on the bridge outer roadway GP lanes, along the entire 1-90 corridor.  Spending far less than the $3.6B could provide the parking required for access to buses as well as fund the added buses.  That using the center roadway for inbound and outbound buses rather than light rail trains would benefit the entire area. 

Instead the Times, rather than questioning Sound Transit’s decision to spend $712 million on the cross-lake portion of East Link, describes it as “costing far less than building another bridge”.  It’s “unlikely” future cross-lake commuters will be enamored with the Seattle Times's “less expensive” result.