At last week’s Sound Transit Board Meeting (video here), one of the more interesting reports was the staff analysis of the D2 roadway, which runs between I-90’s Rainier Freeway Station and the Downtown Seattle Transit Tunnel. There are also PowerPoint slides.
No matter what, these lanes will be closed to all traffic during track construction later in the decade. But afterwards, Sound Transit has always assumed that the 554 would terminate at either Mercer Island or South Bellevue Station. Metro has five peak-only routes that serve the I-90 corridor: the 212, 214, 215, 216, and 218, which together amount to about 18 trips per hour in the peak, that it might prefer to keep running into downtown. In 2010, these added up to about 1 million rides a year, or about 4,000 per day*. For these routes, there are four main options:
- Run joint operations on the roadway, as is currently done in the DSTT. This doesn’t necessarily mean buses would still run in the DSTT itself, but will create similar reliability and schedule impacts to both buses and trains. This is the baseline assumption in the ST budget.
- Run trains only on the roadway, forcing buses to access downtown via Rainier Avenue and S. Dearborn St. This speeds up the trains a bit but makes the buses slower and much less reliable. It saves on capital costs but Metro will pay more to operate buses.
- Terminate Metro buses at Mercer Island or South Bellevue. This creates at least some transfer penalty for bus riders, but keeps trains fast (carrying the bulk of the riders) and saves Metro about 15,000 service hours annually, or around $1.5m, that could be invested in more service on these or other routes.
- Squeeze the tracks on one side of the roadway, allowing a one-lane busway for peak-direction trips. ST staffer Ric Ilgenfritz testified that this is likely cheaper in capital expense than the joint operations option. See the illustration, along with some discussion, below the jump.
FTA requires an (apparently not very binding) “Record of Decision” next month, and Metro and Sound Transit have converged on specifying a rail-only roadway for now, with strong emphasis on further development of the busway option. At the moment, ST needs FHWA and WSDOT approval, as well as more engineering, to be sure that the busway is feasible. The busway is described as Metro’s “strong preference.”
The chart below captures the time impacts to both bus and rail riders for each alternative.
There are two important considerations missing from this chart. First, the number of riders on East Link is likely to be an order of magnitude greater**. Secondly, there’s no consideration of reliability. The joint use options introduce error bars for both modes; the surface option is great for rail but horrible for buses.
The “bus intercept” case is an interesting one. As Mayor McGinn noted in the meeting, the quality of the transfer at Mercer Island is very important to this calculation. The current 2030 operational plan is trains coming every 4 minutes from Northgate and splitting into two 8-minute headway lines. (In the peak, the 4 minute headways will go all the way to Lynnwood.) Even with a high quality transfer, the penalty would therefore be from zero to 8 minutes for buses coming in at random from points east. In the outbound direction, however, it’s practical to schedule buses to depart shortly after trains arrive, and to hold departure until they do.
Personally, I think the busway and bus intercept options are the most acceptable. Joint use will make Link interlining operations a nightmare, and the surface option is so horrific that smart riders will probably transfer to rail anyway, particularly in the afternoon. Between the two good options, it really comes down to the feasibility of the busway and as to whether the saved bus hours from intercept could be better deployed elsewhere. Personally, to encourage good land use and car-free lifestyles, I’m all for de-emphasizing peak expresses in favor of other service, so I’d favor the intercept. But reasonable people can disagree.
* Although some of these are contra-peak on the 212, and would not benefit from the busway option. I’m also not counting the 217, which is all contra-peak.
** East Link projects 50,000 a day in 2030, though I don’t know what share of that is on this segment. It’s likely to go down a bit as economic models adjust to current reality. The Metro routes added up to about 4,000 a day in 2010. So it’s hard to say what the precise ratio is.