Reducing I-5 Corridor Travel Time

A recent Seattle Times Traffic Lab article reporting, “Everett to the north now endures the nation’s worst highway delays” is well founded. However it shouldn’t be “new news”.  A PSRC May 8^th, “Stuck in Traffic: 2015 Report” included charts showing I-5 HOV travel time from Everett to Seattle during peak commute had increased to 75 minutes in 2014.  It’s undoubtedly increased since them.  Recent WSDOT data show frequent 50-60 min. HOV travel times for the Lynnwood-to-Seattle portion.

The problem is too many vehicles are using the HOV lanes.  Limiting traffic on HOV lanes to 2000 vehicles per hour (vph) has long been accepted as a way to maximize vehicle capacity and attain lane velocities of 45 mph.  Limiting traffic to 2000 vph would reduce the 26.7-mile Everett-to-Seattle HOV commute to 35.6 minutes, the 15.2-mile Lynnwood-to Seattle to 20.3 minutes. 

Sound Transit is currently planning to spend more than $5B extending Central Link from the University Station to Lynnwood.  Yet they’ve made no plans to significantly increase parking for access to the extensions.  Thus the light rail extensions will presumably be used to replace the current Snohomish Community Transit and Sound Transit 510-512 bus routes from Lynnwood and the Metro 41 routes from Northgate.  However, the 20 to 25 bus routes per hour that will no longer be routed into Seattle will do little to reduce HOV traffic to 2000 vph.  (The fact that any riders added by the transfers will, at least during peak commute, displace current riders further reduces the extensions "efficacy".)  

The only way to maximize vehicle capacity and attain 45 mph velocity is to implement HOT with fees raised to what's required to reduce the number of those willing to pay to where total traffic is limited to 2000 vph.  (+3HOV won’t assure 2000 vph though it could be used until HOT was implemented.) The way to increase transit capacity and to minimize the HOT fees needed is to make 100-200 of those vehicles added high-capacity buses.

A 70-ft articulated bus can accommodate up to 119 sitting and standing riders.  Thus adding 100 high capacity buses to those currently operating would provide more than 10,000 additional riders each hour with commutes into Seattle; the equivalent of adding 5 lanes of freeway.  Again, the increased number of commuters riding the buses would reduce congestion on the remaining lanes, reducing the HOT fees needed to limit traffic volume.  

The added bus routes could provide express bus routes from 10 or more P&R’s directly into Seattle.  Access to the P&R’s would be provided by local bus routes through areas where commuters live.  Surveys of those working in Seattle could be used to determine how to allocate the added bus routes among P&R’s and when and where to route local buses to those P&R’s. (Local bus routes avoid the need to spend more than $50,000 for parking to provide access for a single driver)

The additional bus routes would be facilitated by converting 4^th Ave into an elongated T/C with each route having one or two designated drop off stations on one side and pick up stations on the other.  However, prior to doing so the buses could continue on an HOT lane to one of 10 or more P&R's along I-5 corridor south of Seattle.  Again, access at each P&R could be supplemented with local bus routes.

The bottom line is Sound Transit is planning to spend billions on light rail extensions that will do absolutely nothing to change the fact, “Everett to the north now endures the nations worst highway delays”. The loss of the viaduct will increase the already heavy congestion on I-5 south of Seattle. Implementing HOT on single HOV lanes with added bus routes could reduce  both HOV and GP lane travel times along the entire corridor; dwarfing the benefits of light rail at a fraction of the cost and time.

Until the Sound Transit Board, the Seattle Times Traffic Lab, the House and Senate Transportation Committees recognize that reality the area’s traffic delays are only going to increase.