If you have complaints about the current service provided by RapidRide C or RapidRide D, just be glad you didn’t try to commute from West Seattle or Ballard to downtown 30 years ago using Metro routes 15 or 18.
The maps for the 15 and 18 show that their 1985 routings hadn’t changed much from 1941 when those routes were established as part of the original electric trolley network. Both routes added service north of NW 85th Street when they were dieselized in 1963, but those are the only obvious service additions I can see. The 1941-63 trolley version of route 18 did have 2 branches south of Morgan Street in West Seattle: the 18 Fauntleroy as pictured in the link above and the 18 Gatewood which is today mostly covered by route 22. The 15 West Seattle also had 2 branches in West Seattle: the branch to Alki that is shown in the 1985 map and another branch that was routed through the Admiral District/Genesee Hill area (similar to the current route 57). The bifurcated versions of the 15 and 18 in West Seattle continued to be operated by diesel coaches until 1978 when the Genesee Hill and Gatewood segments of the 15 and 18 were combined into a new route (the 49).
In 1985, the 15 and 18 followed identical routes from approximately Harbor Island to just north of the Ballard Bridge. Together, they provided local service on 1st Avenue South in SODO and operated through downtown Seattle on 1st Avenue to the Seattle Center and Ballard. Midday headways on both routes was 40 minutes, which provided service every 20 minutes for Interbay, downtown and SODO; but Alki, Fauntleroy, 15th Avenue NW and 24th Avenue NW only saw a bus every 40 minutes. Today, most of those corridors get headways of 15 minutes or less.
At night, service on route 18 improved to 30 minute headways, but route 15 was served by the always unpopular Night Shuttle service. On the north end, the 15 operated only from Blue Ridge to the Ballard Bridge on a schedule that created a timed meet with the 18. The riders on route 15 would then transfer to the 18 to complete their trips to Interbay, Seattle Center or downtown. Going from downtown to 15th Avenue NW required catching the 18 in downtown Seattle and transferring to the 15 Night Shuttle by the Ballard Bridge. On the south end, a similar transfer point was established near Harbor Island. The 15 shuttle buses were supposed to always wait for the 18 before leaving the transfer point, but I can testify that there were plenty of times when the Night Shuttle bus left without waiting for its transfer load.
Today, 30 years later, the 15 and 18 network has been replaced by a number of frequent service routes. RapidRide C, RapidRide D, the 40 and partial service from the 21 have all replaced segments of the service provided by routes 15 and 18 in 1985. Plus, we’re seriously entertaining plans to build frequent light rail lines to both Ballard and West Seattle. I wonder how much progress will be made in the next 30 years.