With University Link under construction and Sound Transit 2 to follow, service frequency has become a hot topic.
Today, Link operates at peak frequencies of 7-8 minutes, dropping to 10 and finally 15 minutes during off-peak periods and on weekends. With average October weekday ridership of 16,200, today’s peak frequencies meet demand and will likely continue to through the next few years, but U-Link will change that.
The North Link Final Supplemental EIS operating plan summary (PDF), which only covers S. 200th to Northgate, the extent planned for in Sound Move, calls for 6 minute peak headways end to end by 2015, with an eventual increase to 5 minute headways between Northgate and Rainier Beach (referred to as “Henderson” in the document) sometime prior to 2030.
With Sound Transit 2, we’ll essentially get a new line – running from Northgate or farther north to Bellevue. Currently, the East Link DEIS operating plan summary (PDF) suggests four car trains every 10 minutes in 2020, with headways down to every 9 minutes in 2030.
An overall Sound Transit 2 operating plan I saw on paper suggested three 9 minute headway lines – One from Lynnwood to SODO or Rainier Beach, one from Northgate to Bellevue/Redmond, and one from Northgate to Sea-Tac/Federal Way. This would cause three minute headways between every other train south of downtown, and could cause problems in at-grade portions.
There’s another possibility here, though. Sound Transit could operate two lines, one from Lynnwood to Federal Way, and another from Lynnwood to Bellevue. This would keep headways south of the International District more stable, and make Bellevue headways higher overall. Either way, frequency from Northgate to the International District will be down to four or even three minutes with Sound Transit 2.
The limiting factor is largely the uncertainty associated with the MLK portion of Link – missing a light can add a minute or two to a trip, making it impossible to really shoehorn more trains in without degrading quality of service significantly. If we want another line through downtown, it will need to either go on the surface, or in a new tunnel.