[Important note: this is not an editorial advocating anything. It is an attempt to quickly analyze some planning tradeoffs.]
When Central Link opened, Metro eliminated some redundant lines (194, 42X), but the bulk of I-5 routes from South King County continue to run into Downtown Seattle, at great cost and with a parallel Link line able to carry those people at nearly zero marginal cost. The best place to make a transfer from I-5 is at Rainier Beach Station, although that location has serious problems. What are the tradeoffs?
First, Google Maps pegs the driving time from Exit 157 (MLK) to Sodo Station as 10 minutes, vs. 3 minutes to MLK & Henderson. Link takes 15 minutes from there to Sodo, meaning that in the baseline scenario the transfer is 8 minutes slower. If you like, subtract a minute for buses being slower than cars.
To this time loss, one must add walking time. If Metro did the user-friendly thing and put the stop on the south side of Henderson, there’s a crossing of two not-crowded lanes. Experience at other stations suggest an easy jaywalk that might take a minute, more for those that insist on a signal. Moreover, there will be wait time: for bus to train, the average varies from 4 to 8 minutes depending on time of day; train to bus, typically 8 to 15 minutes.
On the other hand, the Rainier Beach run is essentially uncongested, while I-5 is often not. The gap shrinks with any delay on I-5. Also, the further north the destination, the smaller the gap is. Going north from Sodo, trains have signal priority and limited-stop advantages over buses, and in some cases a tunnel advantage as well. This adds up to between zero and 6 minutes savings to Westlake in the schedules.
Although in some cases time may be a wash, in general trips with this transfer will be slower and this will cost riders. Unlike the 194/Link tradeoff, all of these trips will still require a bus and won’t attract those that refuse to get on one.
On the other hand, by my count Metro runs 295 trips every weekday via I-5 and the busway, plus 179 on Saturday and 117 on Sunday. With a half-hour of savings per trip, that comes out to around 44,000 service hours, of which 26,000 are charged to the South subarea. For comparison, a draft service cut plan last year took about 45,000 service hours out of the South, and that’s before union concessions saved another 20% of threatened service hours. Alternatively, those hours could be redeployed elsewhere, even by roughly halving headways on routes like the 150.
Other fringe benefits include much improved connectivity between Southcenter and its transit-dependent customers in the Rainier Valley. At some operating cost, buses may terminate at Rainier and Henderson, where there is more bus layover space.
Restored service on the low-ridership southern end of MLK is canceled out by reduced connectivity at the Spokane St. busway stop.
Such a shift also frees up capacity in the busway and DSTT, which can provide a new route to West Seattle post-viaduct and improve reliability on Link.
There are also 198 weekday and 68 weekend trips on Sound Transit buses on the busway, all of which are charged to the Pierce County subarea. Sound Transit and Metro also run 84 and 6 weekday trips, respectively, and 62 weekend ST trips, that bypass the busway to go right into Downtown Seattle. I’ve omitted those from the analysis above.
Whether this kind of service change is worthwhile depends ultimately on how you comparatively value intra-South County service with respect to the quickest possible connections to downtown. Everything has an opportunity cost, and resources can be spent on expresses into Seattle or into reducing headways between suburbs. High capacity transit services like Link provide an option, albeit imperfectly, to avoid gutting one to emphasize the other.