What "Traffic Lab" Should Propose for I-405

The Dec. 14^th Seattle Times headline “Get I-405 Toll lanes moving by lifting $10 cap, state told” epitomizes the Traffic Lab's approach to the area’s congestion problem.  It’s purported as a “project that digs into the region’s transportation issues, spotlights promising approaches to existing gridlock, and helps readers find the best ways to get around”.  As previous posts have suggested, while Traffic Lab has conceded ST3 extensions will not reduce congestion on I-5 and I-90 corridors, it has failed to “spotlight promising approaches to the existing gridlock".  This post proposes a “promising approach” they should consider for the I-405 gridlock.

It doesn’t take much “digging” to deduce implementing HOT lanes will always increase congestion on GP lanes.  Reducing congestion on a highway lane requires reducing the number of vehicles on the lane.  The HOT improvements are based on the premise that more drivers of vehicles will be unable to meet the +3HOV requirement than will be willing to pay the tolls.   HOT fees are increased to limit the numbers of vehicles needed to maintain that benefit. 

The result is those vehicles no longer using HOV lanes will increase congestion on the GP lanes.  For example, a PSRC May 8^th, Stuck in Traffic: 2015 Report included a chart  “I-405 Delay: Lynnwood to Tukwila”.  It showed the delays prior to HOT implementation didn’t even begin until Bothell.  Yet an Oct 1^st Seattle Times B-1 article reported velocities between Lynnwood and N. E. 160^th averaged only 24 mph between 5:00 and 9:00 a.m.  (They were “likely” even slower when most were commuting.)  The WSDOT claim of “occasional time savings for all users” is absurd and it should be no surprise “more than 32,000 people signed an online petition to cancel the tolls". 

The purported reason for the tolls is to satisfy federal HOV standards requiring  “lanes must flow 45 mph or faster at least 90% of peak commute times”.  (It’s not clear why the standard doesn’t apply to I-5 corridor.)   The Traffic Lab could propose a relatively easy way to not only meet the federal standard, they would also reduce GP lane congestion. 

Between Lynnwood and Bothell the current HOT lane would be converted to a GP lane, eliminating the 45 mph requirement.  The WSDOT could expedite adding the 4^th lane for HOT tolls that could be raised to whatever is needed to achieve the 45 mph requirement.  Between Bothell and Bellevue, one of the two HOT lanes would also be converted to GP.  Again, the tolls on the remaining HOT lane could be raised to whatever is required to achieve the 45 mph requirement. (Typically limiting number of vehicles to 2000 per hour).  

Implementing the additional GP lane would reduce congestion for the vast majority of commuters along the entire route.  The increased velocities between Lynnwood and Bothell would reduce the delays for those wishing to pay tolls until the HOT lane is added.  Between Bothell and Bellevue, those willing to pay the fees needed to meet the 45 mph requirement would still be able to do so. 

The Traffic Lab support for “lifting $10 cap” is consistent with the Seattle Times June 26^th headline, “Time to pay?  Tolling doesn’t get much love, but it eases gridlock”.  It’s time they “spotlighted OTHER approaches to the existing gridlock”.