Today is the last day where buses would operate in the Downtown Transit Tunnel in Seattle. Starting tomorrow the tunnel would be rail only with Sound Transit Link service to SeaTac and UW, but will eventually expand as multiple extension projects complete to Northgate/Lynnwood, Bellevue/Redmond, and Federal Way.

I had a chance to visit that tunnel in 2015, about a few months before the Link expanded to UW. I found this unique sharing arrangement between buses and transit to be very cool.

Most of us grow up with very distinct experiences between riding the bus and rail. With buses, you board the bus on the street, you pay as you board, and you ride along with car traffic stopping at every red light. With rail, we go to a dedicated station, buy tickets and go through fare gates, walk up or down to reach the platform and ride the train away from traffic. With this system, you may board a bus normally on the street on one end, but you would arrive in a downtown subway traffic free as if you’re riding on a subway train, but without the hassle of transferring systems like you would almost anywhere else, even the most transit oriented cities around the world.

Many transit systems have rail vehicles operate like buses on the surface (streetcar/tram), but running buses underground like a subway, especially where the tunnel is shared with rail, is truly one of a kind.

Some suggested that the tunnel should be built for rail to begin with, but I think that almost 30 years of bus use in the tunnel, with nearly 20 years of exclusive bus use, proved its worthiness as a bus facility. Under this arrangement, Seattle was able to build its rail system in an incremental basis, to build one of the most expensive and essential infrastructure early on, and to put it to daily use without having the rest of the rail system done. That 30 years of bus use meant two generations of bus fleets. The first generation was a fleet of diesel dual mode vehicles: operate with diesel engine on the surface and off trolley wires underground. The second generation is a fleet of hybrid buses. The trolley wires for the bus had to be removed because it would conflict with overhead lines for rail. Newer hybrid technology for the 2nd generation of bus fleet reduced bus emissions so they could operate safely underground.

Given that many transit systems are pursuing bus rapid transit (to operate buses more like rail with dedicated right of way and/or stations), not operating buses in tunnel is a set back to some degree. To accommodate the extra bus traffic on downtown streets, the city recently designated bus lanes on certain streets and the transit agency will be instituting all door boarding. However those on street traffic treatments are far from unique with varying degrees of success. Also picking up buses curbside on downtown streets will not be anything close to boarding buses inside a subway station.

I wished that Seattle somehow finds a way to continue tunnel bus operations, but we all know that it will come to an end as the region commits to more rail expansions.