Reducing I-405 Corridor Travel Times

A previous post detailed how diverting light rail funds to expanding bus transit capacity along an I-5 HOT lane could reduce corridor congestion.  This post details how expanded bus transit capacity along a single HOT lane would reduce I-405 corridor travel times. 

That WSDOT plans for implementing 2 HOT lanes between Lynnwood and Renton are far more about increasing revenue than reducing travel times.  That Sound Transit needs to end its decade long refusal to increase bus transit capacity.

Travel times from a Jan 23, WSDOT 7:55 am traffic report exemplify I-405 congestion.  The report’s 89 minutes for the 26-mile Everett-to-Bellevue commute and the 61-minutes for the 16-mile Lynnwood-to-Bellevue commute show WSDOT decision to implement 2 HOT lanes has failed to reduce GP lane congestion. 

The report’s 45-minute HOV travel times from Everett and 33-minutes from Lynnwood show average velocity was far less than the 45 mph WSDOT committed to provide for those who were paying I-405 HOT fees.  The problem being limiting GP to 3 lanes between Bothell and Bellevue increased congestion to where, during peak commute, the number of commuters willing to pay the tolls exceeded the 2000 per hour needed to assure 45 mph.

Meanwhile, south of Bellevue, the 11-mile, Renton-to-Bellevue travel times were 60 minutes on GP lanes and 33 minutes on HOV lane.   Those travel times were the major reason the 23-mile Federal Way-to-Bellevue commute took 83 minutes on GP lanes and 51 minutes on HOV. 

Clearly south-end commuters using the I-405 corridor also deserve better.  The WSDOT is finishing spending nearly $200 million on their SR167/I-405 “Flyover Connector” from SR167 HOT lane to I-405 HOV lane.  They’re scheduled to begin adding a 4^th lane from Renton to Bellevue this year. Yet neither will significantly change travel times because the WSDOT is planning to implement HOT not only on the new lane, but on the existing HOV lane as well.  

Again the 2 HOT lanes restrict GP traffic to two lanes, increasing congestion to where more that 2000 drivers per hour will be willing to pay the HOT fees than the HOV lane can accommodate and still attain 45 mph.  The only beneficiary of the two HOT lanes is the WSDOT since more riders will be paying tolls on 2 HOT lanes to avoid GP congestion, even if they don’t attain 45 mph.

The solution is to implement HOT on a single lane for the entire I-405 corridor with fees set to where those willing to pay limit total HOV traffic to 2000 vph.  The additional GP lanes would reduce congestion but the biggest benefit could come if Sound Transit were to add 100 high capacity bus routes an hour along the HOV lane.

The assured 45 mph commutes with the added bus capacity could attract more than 10,000 additional transit riders each hour, adding the capacity of 4 lanes of freeway; reducing congestion and the incentive to pay tolls (and WSDOT revenue.)  Instead, Sound Transit 3 plans for when I-405 BRT routes begin in 2024, require a minimum of 10-minute headways between buses, limiting frequency to 6 buses an hour.  That projected daily ridership will be limited to 15,000 – 18,000: a fraction of what’s required to reduce I-405 travel times. 

Sound Transit’s version of I-405 BRT is exemplified by their ST 3 plans for the route from Lynnwood to Bellevue T/C. It includes stops at Canyon Park, UW Bothell, Brickyard, Totem Lake, and 85^th St near Kirkland.  (Sound Transit is spending $300 million on the 85th St T/C but nothing to add parking for access.) Their current 535 bus schedule shows all the intermediate stops result in 50 minute commutes between the two.

They fail to recognize that during peak commute the 100 added buses each hour could be allocated to routes from one of ten or more P&R lots along I-5 from Everett and along I-405 to Bellevue with routes directly to either Bellevue or Overlake T/Cs. That avoiding all the intermediary stops and 45 mph speeds would slash commute times. (Current bus routes would continue)

Those working in both Bellevue and Overlake would be surveyed to determine bus schedules for each P&R to Bellevue or to Overlake.  Access to P&Rs could be augmented with local bus routes where needed.

Meanwhile Sound Transit’s I-405 BRT south of Bellevue should include similar plans to allocate the 100 buses an hour to routes from P&R lots along I-405 to Burien and along I-5 to Federal Way and beyond to Bellevue or Overlake T/Cs. Again surveys will be used to schedule bus routes and local routes needed to provide access to P&R. (Neither Metro nor Sound Transit currently provide any I-405 bus routes between Federal Way and Bellevue.)

The bottom line is current I-405 congestion is only going to increase with WSDOT's plans for 2 HOT lanes. That Sound Transit plans to spend $812 -$869 million implementing BRT consisting of a single route from Lynnwood to Burien every 10 minutes does little to reduce I-405 congestion.  That spending $300 million of those funds on a T/C near Kirkland with no parking for access does little to increase transit ridership.

Reducing I-405 travel times requires Sound Transit add high-capacity bus routes from up to twenty P&R lots along both I-5 and I-405 to Bellevue and Overlake T/Cs.  That WSDOT facilitate those routes by limiting HOT to one lane with fees set to limit traffic to assure 45 mph.  Again, until that happens I-405 travel times are only going to increase.