Light Rail is Best for West Seattle
I ran Ross's Open BRT plan for West Seattle because it's a good analysis of the best the region could do with a budget roughly four times lower than what it takes to build light rail to West Seattle. There are many reasons Sound Transit may need to economize on the West Seattle segment, and in that case they could do worse than to follow Ross's blueprint.
But Ross's thesis is much stronger: that BRT would be better than light rail for most riders, largely because an open BRT system would avoid transfer penalties. This runs counter to a lot of work on STB that shows the merits of a transfer-oriented system, which largely involve the operating savings of not running downtown to enable other trips. This aspect doesn't appear in Ross's work because he completely punts the issue of operations. This is crucial, because it's in the operational details where claims of "rail-like" BRT collapse.
(1) One can only assume that Sound Transit 3 would pay for the excellent capital projects Ross proposes. But does ST actually take over operations on the C Line, 21, 120, 37, 55, 128, 116, and all the other buses duplicating each other on the bridge? If so, that's a lot of ST's taxing authority tied up in running buses forever. It also assumes an unprecedented level of ST bus service provision in this corner of the region, and other corners without light rail may wonder why they're not getting the same. Both problems would kneecap ST's ability to deliver big capital projects.
If Metro keeps running these buses, then that forfeits the opportunity to seriously increase the frequency of buses within West Seattle. This not only would cut headways to board the bus, thus eroding the putative time advantage of no transfer to light rail, but would also improve all intra-West Seattle trips.
(2) On a related note, Ross blithely asserts that his BRT system will have off-board payment. Off-board payment either requires turnstiles (and someone to monitor them) at all stops (which is not going to happen), or fare inspectors, which are one of the big cost differences between light rail and traditional buses. But this is an open BRT system! So are these routes fully equipped and staffed over their entire length, with machines at essentially every bus stop in West Seattle, or do the rules change when they enter the BRT zone? If the latter, then that will impair reliability of what feeds into the zone. Or is it, as I suspect, not really going to be 100% off-board payment?
(3) Headways will not be evenly distributed in the core West Seattle-to-downtown BRT corridor. Buses coming in from various points on the peninsula will inevitably bunch, creating platoons that are train-like except for their traffic separation and labor costs. These buses are not going to get the nearly-perfect signal priority that Link gets, simply because there are too many coming at too many arbitrary times to support that and maintain a decent traffic level-of-service.
(4) Ross relies on ramp metering to reduce bus lane congestion on the West Seattle bridge. But what about when things really go south there? Will cars line up across the bus lane from the Delridge on-ramp waiting to merge, or will the ramp-meter simply turn to solid red when the bridge simply can't take any more cars? I have my suspicions! A system that still relies on the single point of failure of the bridge isn't the gold standard for West Seattle.
(5) The plan also points out how cheap bus lanes are, and how they're being done elsewhere in the city. Bus lanes on all the feeder routes are an advantage over a baseline light rail scenario. But there are logically two possibilities here: bus lanes are cheap and politically easy, in which case they are in no way incompatible with a light rail scenario; or they're actually very difficult because of local opposition, in which case they're not so cheap and easy and may not materialize. In neither case are outlying bus lanes a discriminator between core BRT and core rail.
Sound Transit isn't immune to these problems either, but they overcame it by spending money. They didn't simply take two train-widths out of the MLK roadway; they rebuilt the entire road, on a wider footprint, to preserve general-purpose lanes. They also launched a community development fund to help businesses that suffered construction impacts. A cost of doing business in Seattle if you're building high-quality transit, this is baked into the cake of the light rail cost-per-mile but are usually omitted in theoretical BRT proposals.
On the path from Junction to bridge, those bus lanes compare to (at least) MLK-style Link, eating up more of thr transfer penalty.
(6) After Ross choreographs every detail of the Eastbound movement from the Junction to downtown, there is not a word about Westbound trips. I agree that these trips are a less serious problem than Eastbound. But this omission makes the plan neither futureproof nor robust. West Seattle is growing and the traffic will too. And the entire point of traffic-separated transit is to not melt down when the roads do! The problem, of course, is there are no quick fixes here and there's a need for substantial new right of way. Once the project scope grows that much, the cost advantages of BRT dwindle. Meanwhile the other benefits of rail, a comfortable ride, surge capacity, lack of driver distraction, and seamless wheelchair/bike/stroller boarding, come into scope.
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Many of these results are consistent with "BRT creep:" a line initially promised to be at rail quality gradually degrades into a mildly enhanced bus. A cursory look at the complexities of interagency cooperation and open BRT, the history of trying to win even minor bus reliability enhancements in West Seattle, and management of a freeway with less than total emphasis on transit suggests a bus line to West Seattle is particularly susceptible to many of these degradations.
It's completely reasonable, depending on your values, to decide that a rail project to the Junction simply isn't worth it. If you like low taxes more than transit projects, think lines to other areas should have other priority in the scope of a realistic budget, or have contempt for West Seattle as a transit market, then you'd prefer to economize on service there. But you get what you pay for, and the true gold standard to serve West Seattle is light rail.