Reducing I-405 Renton-to-Bellevue Congestion

The December 4th Seattle Times front page Traffic Lab article “Return to office mandates aren’t the only reason Seattle Traffic got worse” details the problem.  That “Seattle sits in 10th place behind only a few of the nation's largest and most traffic-logged cities”.  That “Not coincidentally the stretch of northbound I-405 between Renton and interstate 90 was the most congested roadway in the region, and the 24th most congestion in the country”.  

The article’s culprit: work on the interstates, and return to office mandates by some of the area’s largest employers. Construction to add another lane has been delayed until 2027. The article quotes Bob Pishue,, a transportation analyst at INRIX, “There’s no solution to congestion.”

 

While there may be no solution there are ways to reduce it.  For example the article’s I-405 picture shows hundreds of vehicles but no buses. A high capacity bus can accommodate over 100 riders.The only Sound Transit bus route in area, ST560, runs every 30 minutes. Sound Transit could run buses every 5 minutes, 1200 riders per hour, and add parking if needed for access.

 

The expectation for reduced travel time with added fourth lane is belied by WSDOT plans to use it and existing HOV lane for collecting HOT fares. That current 2-person carpoolers using the HOV lanes will be forced to either pay the fees or join the congestion on the two existing GP lanes between Renton and Bellevue. The WSDOT Friday 8:05 Travel Time for the 10.92-mile Renton-to-Bellevue route was 16 minutes on HOV Lane.  Forcing current HOV lane drivers, unwilling to pay the HOT fees, to GP lanes will add to the current 31 minutes for those already using the lanes

 

Even that HOT benefit could be limited.  During peak commute the resulting increased GP lane congestion will likely result in more drivers willing to pay the HOT fees than the 2000 vph optimum required for 45 mph: Extending travel times for those paying the fees.  During off peak hours those willing to pay the fees will still be restricted by speed limits, but HOV lane vehicle capacity will be wasted. 

 

The bottom line is Renton-to-Bellevue travel times can be reduced by adding parking and bus routes for riders, use added lane for additional GP vehicles rather than for HOT, and limit HOT to a single lane with fees