SR-520 HOV lane designed by anti-transit conspirators

Previously posted on October 7 at:!1phaOgcvNsBxzvBN9Zpx1vbQ!213.entry

The SR-520 HOV lane design must have come from anti-transit conspirators. It’s all I can come up with, lacking any real background info on its design and implementation. Although, to be fair, it’s a pretty awful design for folks in cars too. Perhaps it was designed just to “prove” how ineffective HOV lanes can be?
Ok, let’s talk about HOV lanes. In a functional HOV lane design, you have perhaps 3 lanes going each direction on a highway. From the center outward, it might look like “Hov |  Reg  |  Reg” (where “Reg” is a lane open to any traffic and “Hov” is restricted to bus, motorcycle, and carpool of some sort). Periodically, there are on-ramps merging in from the right, and exits going off to the right. This works great, but it has two minor flaws:
  • If you have a left-exit (not all that common, but they exist) or a left-entrance (not very common at all, in my experience) – they end up having to pass through the HOV lane
  • In the right entrance/exit case, to get onto the highway and into the HOV lane (or out of the HOV lane to exit) requires passing through all other lanes of traffic.

I’ve not seen a solution to the 1st problem, as it’s not particularly common in well designed highways. The solution to the second problem is what is called a “flyover-lane”. Basically, special entrances/exits to the highway that take you straight in and out of the HOV lane. We have this here in Seattle on I-90 and I-405, and they work like a charm!

Ok, so what’s the problem with SR-520? Well, the HOV lanes are on the right. Yes. The right.

This means the highway looks like “Reg  |  Reg  |  Hov”. Can you guess what happens to traffic in the HOV lane? Exactly… every time there’s an on or off ramp, traffic to/from the regular lane has to pass right through the HOV lane, all but guaranteeing that the HOV lane has to slow or stop at every entrance/exit. And it also means that cars that merge on have to find a way to IMMEDIATELY merge (often in stopped traffic) into the regular lane to the left of the HOV lane. This means if you’re merging into 520, you will almost immediately be halfway into stopped traffic in the center-lane, with your car stopped at a crazy angle… and with a bus bearing down on you, the bus having to veer out onto the shoulder to get around you.

Yuck. Who designed this mess?!

I can come up with only three somewhat-reasonable explanations for why we don’t have HOV lanes in the center lane on SR-520:

  • There are no flyover lanes, and flyover lanes are expensive. Ok, this makes some sense. But in my opinion, it still makes more sense to have the HOV lanes in the center lane vs the outside lane… flyover entrance/exit lanes are just icing on the cake. Watching traffic as I travel on 520, it seems to me like there are basically two options for a car going westbound from Redmond to Seattle — no matter where you enter SR-520, it’s probably better than 90% chance you’re either going to stay on to I-405 or you’re going to go across the bridge and into Seattle. Perhaps we just build flyover lanes for I-405 interchange, and let the handful of other HOV drivers who want off between Redmond and the bridge fend for themselves in crossing traffic. It couldn’t possibly be a worse hassle or more dangerous than the current situation!
  • The bus (in the HOV lane) has to keep getting over to the right to get to the various bus stops along SR-520 (Yarrow Point, Evergreen  Point, etc). Ok, this is just a cop out. I’m sure we could figure out another way to do this, even with the total-lack-of-median we find along SR-520. Even something as simple (albeit irritating) as having the bus continually shift back and forth between the HOV lane and the stops would be better than having the HOV lane be totally useless for the whole route!
  • There is no HOV lane across the bridge, so it would have to end rather abruptly just before the bridge – perhaps they’re trying to avoid having the HOV lane back way up from the bridge by making it useless over the whole route? Hehe, whoops, that’s sarcasm. In any case, I don’t see how this is much different than what we’ve got today on I-90 going west. Where the express-lanes begin, the HOV lane abruptly ends and folks in that lane have to merge back into traffic to get into the Mercer Island tunnel.

So having run through all of that, I wonder what is the real reason. If you happen to be a Metro Transit planner or Seattle/DOT planner privy to the real reasons behind the SR-520 HOV lane design decisions, I’d love to hear from you!



  1. Evan Dodds - Non-work-related blog » Bus spacing said,

    January 7, 2006 at 6:33 am

    […] We’ve already been on the bus for ages, stuck in the terrible HOV lanes on 520, so I’ve probably already missed one or more 48 buses I might have caught if there had been no traffic. […]

  2. Evan Dodds - Non-work-related blog » Some bus drivers are not very good people said,

    February 10, 2006 at 6:15 pm

    […] I catch the SoundTransit 545 express bus home from work when I ride the bus. It’s generally a nice ride, apart from the fact that 520 is at a dead stop (even in the wonderfully designed HOV lane) most days so it’s hardly an express. […]

  3. Evan Dodds - Non-work-related blog » I’ll call it “Lousy Busride Tuesday” said,

    June 7, 2006 at 6:56 am

    […] The ride on 520 was garbage since the HOV lanes were stop and go the whole way. But eventually we got to Montlake. By this time it’d taken about 50 minutes to go the (according to Streets and Trips) 10.2 mile trip. […]

  4. Evan Dodds - Non-work-related blog » More Bus Adventures said,

    November 3, 2006 at 8:14 am

    […] But not yesterday… yesterday I had a seat and I was glad to have a bus-driver who drives the thing like a taxi. Everything but up-on-the-grass to go around stupid drivers who stopped in the defective 520 HOV lane while trying to merge in, etc. Good stuff! Excepting the 20+ minute slow start, we made it into the city even faster than we’d have made it on a lot of typical high-traffic days! Sweet! […]

  5. Evan Dodds - Non-work-related blog » We so desperately need rail transit here in Seattle said,

    January 13, 2007 at 7:48 am

    […] And that doesn’t even take the daily commute benefits of rail (overcoming traffic caused by traffic, not by bad weather) into consideration. Grade separated rail that can avoid the terrible HOV lanes on 520. Grade separated rail that can be FASTER and MORE RELIABLE than driving myself to work. I’d take that 5 days/week. […]

  6. Evan Dodds - Non-work-related blog » 520 Transit lanes NOT designed by anti-transit conspirators said,

    February 13, 2007 at 8:09 am

    […] Turns out I was wrong. I’d previously referred to the “right-hand-side-of-the-road” HOV lanes on SR-520 as having been designed by anti-transit conspirators. […]