Traffic Lab Still Doesn’t Get It

The previous post detailed why Smarter Transit was “too little too late” with Its August 8th opinion letter “Demanding greater accountability, transparency before ST3 expands”.  This post details why the Traffic Tab doesn’t recognize the Northgate-to-Lynnwood extension August 30^th debut “won’t fix what ails adjacent I-5”.

What ails I-5 is too many cars or too few lanes. While the Northgate-to-Lynnwood extension adds another “traffic lane”, its capacity is limited because light rail trains are restricted to 4-cars. That safe operation requires 4 minutes between trains. Assuming each car can accommodate 150 riders, light rail spine capacity is limited to 9000 riders per hour. (With or without the Line 2 trains)

 

Thus, the August 15^th Traffic Lab question, “How much can light rail help?” doesn’t “get it”.  Accommodating the Sound Transit’s 2024 service plan predicted “25,300 to 34,200 daily boardings” would end access for Northgate-to-Westlake riders for much of the day. Especially since initial operation will be limited to trains every 8 minute or half that capacity. (That's about half the 67,000 riders former Sound Transit CEO Rogoff had predicted in a 2017 FHA Lynnwood extension grant application) Even worse, many if not most are not new transit riders but Snohomish Community Transit (SCT) riders currently using the Lynnwood extension:

Commuter routes to Northgate and Seattle will be eliminated and replaced with new express and local routes that connect to light rail.

Thus, on Sept. 15th, SCT will force all 400 series riders to transfer to and from the Lynnwood extension for the commute into and out of Seattle. (It’s not clear how the bus riders transferring to and from light rail will pay the fares.) Reducing bus routes into Seattle reduces transit capacity and nothing to reduce I-5 GP lane congestion into the city.  

The SCT 400 series riders will reduce access for the Northgate-to-Westlake commuters, though many will be dissuaded by the need to transfer and the loss of more convenient stops for egress and access along 3^rd Ave than at the Westlake Station with everyone else.

 

Again, whatever riders the Lynnwood extension does attract will reduce access for current Line 1 riders.  The SCT response is a new 515 route from Lynnwood City Center Station into and out of Seattle, presumably during peak commute hours.  (They also intend to continue routing 510 from Everett with multiple stops along I-5 and 7th and 5th Ave in Seattle for egress and access for the return during peak commute hours.)  

 

Thus, many Lynnwood commuters will likely opt to ride 515 into and out of Seattle rather than light rail during the peak commute.  However, it’s not clear how they intend to schedule 515 to prevent Lynnwood commuters from “clogging” Line 1.

 

The bottom line is the Traffic Lab still doesn’t “get it” that the ST/SCT plan to use the Lynnwood extension to replace bus routes will reduce transit capacity into Seattle, do nothing to reduce I-5 GP congestion, and results in operating cost during off-peak operation that will dwarf any fare box revenue riders pay.  Even more important, it's a precursor of results from future light rail spine extension along I-5 and across I-90 bridge.