An earlier post concluded “the March 1st $5.00 increase just adds to the debacle of WSDOT imposing HOT on two HOV lanes”. The debacle being the WSDOT apparently doesn’t understand the rationale for imposing HOT fees on HOV lanes. That HOT can be used to reduce multilane freeway congestion by imposing fees on an HOV lane to achieve 2000 vehicles per hour. More vehicles slow traffic below the 45mph optimum for maximum capacity and fewer vehicles waste capacity that could be used to reduce GP lane congestion. The HOT fees can be adjusted throughout the day, raised to limit traffic during peak commute and reduced during off peak to attract the 2000 per hour that minimizes GP lane congestion.
The WSDOT approach to HOT on I-405 between Bothell and Bellevue was to limit the fees but to impose them on two lanes, increasing congestion on the remaining three GP lanes. The WSDOT 2023 Express Toll reported the Bothell-to-Bellevue section achieved average speeds of 50 mph or greater: the Lynnwood to Bothell 46 mph, both during the peak period”. Thus prior to the decision to increase HOT fees the higher-than-45 mph speeds were already wasting capacity and doing so on two lanes between Bothell and Bellevue. The effect on the $5.00 increase on travel times is reflected on the WSDOT website wsdot.com Travel Time for routes between Bothell and Bellevue, and Lynnwood and Bellevue. Subtracting the former from later can be used for Lynnwood to Bothell.
The average travel times for March 5th,6th, and 7th at 7:45 am were assumed to reflect $15 tolls for the morning commute and 4:45 pm for the return commute. The GP travel times between Bothell and Bellevue were 16.3 min and 44 min from Lynnwood to Bellevue. Comparable HOT travel times to Bellevue were 9 min from Bothell and 25 min from Lynnwood. Subtracting the 9.4-mile Bothell to Bellevue section from 15.2-mile Lynnwood to Bellevue give 5.8 miles for Lynnwood to Bothell. Subtracting the time for the Bothell to Bellevue from the time from Lynnwood gives travel times from Lynnwood to Bothell as 27.7 min on GP lanes and 16 min on HOT lanes.
The 9 min HOV travel time for the 9.4-mile route between Bothell and Bellevue gives a 62.7 mph with the $15 fee, an indication the resulting reduced traffic did not result in commuters driving significantly faster than reported by WSDOT with $10 fee. However, the additional traffic on GP lane increased travel time to 16.3 min and 34.6 mph, increasing the penalty for not paying the fee from the 9 min reported by WSDOT for $10 fee to 28 min for $15. The 27.7 GP and 16 min HOV travel times for 5.8-mile Lynnwood-to-Bothell gives 12.6 mph on GP lane and 21.7 mph on HOT lanes, less than half the 46 mph the Washington Transit Commission quoted. A clear indication the $5.00 increase did not reduce travel times.
A similar analysis for the 4:50 pm return times gives travel times and speed as 30 min and 18.8 mph on GP lane and 13 min and 44.8 mph on HOT lane from Bellevue to Bothell, increasing the 23 mph HOV advantage with $10 fee to 26 mph. However, the 12 min on GP lane and 7 min on HOT lane on the 7.1-mile return trip from Bothell to Lynnwood gives 35.5 mph GP and 60.8 mph HOT lane velocity, three times the inbound velocity. The reason being WSDOT added a GP lane of traffic along the route.
The bottom line is the three days of travel time data show reducing congestion on HOV lanes doesn’t assure increased velocity or reduced travel time. However, increasing congestion with additional traffic from those deterred by increased fees, significantly reduce velocity and increased travel times. That on the Bothell-to-Lynnwood segment adding a GP lane dramatically increased both GP and HOV lane velocity. A strong indication converting one of the two HOV lanes to a GP lane would reduce travel times between Bothell and Bellevue. And reaffirming the recommendation the added lanes along the rest of the route also be used for GP traffic not HOT.
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