Every once in a while, someone asks me how long it will be before the buses are kicked out of the tunnel downtown. I bet we’ve talked about this before in the comments, but we could do with a discussion of frequency and routes.
At launch, peak train frequency will be 7.5 minutes. It’ll be listed as 7-8 minutes on the schedule – Metro’s scheduling system doesn’t handle 30 second increments. I was hoping for 6 minute peak headways, but we’ll get them eventually. As the first year of operation is only projected to average out with 20-25,000 on weekdays, I think we can wait a bit for 6 minute peaks.
I’ve been told that somewhere around 5 minute headways, there’s no longer safe time for buses to get through and load between trains, and at that point they’ll go back out to third avenue and elsewhere. That may happen when University Link opens, as ridership demand skyrockets. As we saw during the tunnel closure, surface congestion isn’t that bad with the extra buses, and a number of the tunnel routes will be replaced by rail soon after anyway. Perhaps at that point, we’ll consider further separating the bus corridor from cars.
When ST2 lines are built out, the expectation is that we’ll drop to 3 minute headways. The ST2 planning documents I’ve seen show three ‘lines’ – Lynnwood to Sea-Tac, Northgate to Federal Way, and Northgate to Redmond, each running on nine minute headways to combine to three between Northgate and ID Station. But we’d end up with headways of 3/6/3/6 minutes in the Rainier Valley, and I’m not sure 3 minute headways there would be feasible.
A little bird told me that a better option might be two six minute headway lines – one all the way from Lynnwood to Federal Way, and one from Lynnwood to Redmond. I like this better, it would cause far fewer passenger headaches. Oh, and wouldn’t it be awesome for the two lines to be Purple and Gold? It’s not my idea, but I like it.
Okay, how about the longer run? We should be able to get headways down to 2 minutes north of ID Station. At that point, in fifty years, we’re probably going to want to increase speed to Sea-Tac anyway. This is pure speculation, but I’ve mentioned in the past that it’s interesting that we leave and return to the Duwamish valley with Link. An elevated bypass along Marginal Way could save a couple of minutes for trains to the airport, serve SoDo better (with a stop near Georgetown), and allow us to add stations at Graham St. and S. 133rd without affecting longer distance users.
Consider this an open thread.