The cost of HOV-2 on I-405

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Any regular transit rider coming home from Bellevue, in a bus, in an HOV lane on I-405 southbound, knows well the feeling of moving 0-5 mph. Granted, it's not always like this. There are certainly some days where it zips by traffic at nearly 60, while some other days it takes over 20 minutes just to get to I-90.

While unreliable HOV travel times are already quite frustrating, very often traffic flow in the HOV lane ends up being as bad or worse than in the general purpose lanes! Why is this tolerated by WSDOT, when the whole point of an HOV lane is to flow faster as an incentive for people to carpool or take transit? Why would anyone want to do this if they are just going to get stuck in the same traffic as if they drove alone?

I-405 south of Bellevue is getting the same type of express-toll lanes as to the north, but not until 2024. You would think that making the current HOV lanes HOV3+ would be a natural precursor to the eventual ETL extension, but WSDOT would not agree.

But how many service hours might be saved if HOV3+ were in place on I-405, in particular from Renton to Bellevue? In this calculation, I'll assume that traffic in the HOV3+ lanes always moves at 45 miles per hour or better. That is the standard which WSDOT attempts to maintain for the express-toll lanes generally, and is also the point at which WSDOT says it will consider upgrading HOV2+ lanes to HOV3+ (though clearly that doesn't seem to mean anything in practice).

This calculation is going to be extremely rough for many reasons. Not only are actual vehicle speeds variable, but it's also hard to figure out how much of the time buses use the HOV lane, since (on I-405 in particular), it often varies not just by route, but by driver. 560 operators often pop into the HOV lane between Kennydale and Newport Hills freeway stations (possible because each direction is only 3 lanes wide), while on other routes (select 566 trips and Metro routes) operators tend to stay in the right lane, not wanting to risk missing the next exit.

My analysis assumes trips serving these freeway stations do not utilize the HOV lane until north of Newport Hills freeway station. It also only calculates based on two major congestion cases (I-405 south from NE 6^th to Newport Hills in the afternoon, and I-405 north from Southport Drive to NE 6^th in the morning), to approximate time savings for the most consistent slowdowns (southbound from NE 6th to I-90, and northbound from SR 167 to Coal Creek Parkway SE). Outside these scenarios, the HOV lane tends to be effective. I am most likely to underestimate the savings, since I only count cases where the time savings is reasonably clear. As such, certain routes are excluded from the analysis. Route 342 only operates in the reverse-peak direction. Routes 111 and 114 make relatively closely-spaced right-hand exits on the freeway. And in the northbound direction, routes 560, 167, and 952 are also excluded since the northbound analysis considers only congestion south of Coal Creek Pkwy. Though the latter will list savings for these routes as "0," there is nearly certainly some non-quantifiable time savings on these trips from HOV3.

Below are the approximate minutes saved per route, per direction, per day. These come from scheduled stops on ST 560 SB and ST 566 NB, and the number of minutes saved if traffic on I-405 moved at 45 miles per hour. ST 560 from Bellevue Transit Center to Newport Hills Freeway Station would take no longer than 9 minutes, and ST 566 from Southport Drive to Bellevue TC would take no longer than 18 minutes:

	560	566	567	167	952	ST Total	Metro Total	Total
SB	39	63*	45*	29*	28*	147	57	204
NB	0**	29	25*	0**	0**	54	0**	54
Total	39	92	70	29	28	201 mins	57 mins	258

*Extrapolated from nearby 560/566 trips **Not able to quantify HOV3+ time savings

Converting minutes per weekday to hours per year (assuming approximately 255 business days per year), then Sound Transit saves 854 annual service hours, and King County Metro saves 230 annual service hours. While only adding up to about $150,000 in annual savings, this is likely to be a signficant underestimate.