LRT vs BRT: West Seattle Needs A Full And Unbiased Analysis


Bus rapid transit (BRT) proponents argue that dense population and growth centers of West Seattle are too spread out to be effectively served by one light rail line, and they’d say even a dual line wouldn’t cut it. It’s a worthy debate that has been extensively hashed out between light rail and BRT evangelists, but one piece of the debate has recently changed. In early December, conversations by Sound Transit staff and decision-makers began to consider a larger investment package for Sound Transit 3 expansion plan.

Instead of a mere $15 billion, the region may see a transit measure closer in size to $25 billion or $30 billion. Naturally, with more monetary resources comes more investment capabilities. At the same time, Sound Transit also released a comprehensive “Corridor Summary” that projected daily ridership as high as 50,000 for its “West Seattle Junction” elevated light rail option and as many as 40,000 daily riders for its Delridge Way at-grade light rail option. That’s as many as 90,000 riders combined for perhaps a $3 billion investment ($2 billion for Delridge and $1.8 billion for “West Seattle Junction” but the two lines share the cost of first three stops and the Duwamish rail bridge thereby reducing the overall cost). Of course you’d have to adjust for the first three shared stations so you couldn’t just add the numbers together. Still, these aren’t paltry ridership numbers when compared to other high performing alignments like Ballard to Downtown Seattle (up to 133,000 daily riders for a $4.7-$5.3 billion investment).

West Seattle Combo
The red line is a light rail routing that I previously suggested for West Seattle; it’s a combination of the 3-A and 3-C options in Sound Transit recent study. I estimated a cost of $3 billion to do both based on Sound Transit numbers.

The skeptics would have you know that several Sound Transit Boardmembers seem to favor light rail to West Seattle and have all but promised an alignment there. They would also suggest that Sound Transit is inventing these numbers out of thin air to ensure that outcome. So who cares what the numbers say?

They might be right. The ridership numbers seem inflated.

Sound Transit should take BRT seriously and appropriately evaluate it. How much ridership would a West Seattle BRT see? How would Sound Transit handle operations? Would they build it and then hand it over to Metro Transit? The key to clarity for high quality transit to West Seattle is Sound Transit studying both light rail and BRT options extensively and honestly so we can make an informed decision.

Buses In The Next Transit Tunnel?

The utility of West Seattle BRT hinges on access to a Downtown transit tunnel to speed trips through the core. Sound Transit recently studied a second transit tunnel, and it seems more and more likely they’ll build it. The big question for BRT fans is whether they will allow buses in the tunnel if built.

Bus and rail already share one transit tunnel in Downtown Seattle, but that relationship has been tenuous at best. Bus operations have always been relatively slow in the tunnel. Increasing Downtown bus trips and combination of new light rail service necessitated the permanent elimination of some routes from the Downtown Seattle Transit Tunnel early on. Then in 2012, the Ride Free Area was ended and threatened increased average boarding times for buses. Metro responded by platooning buses and hiring staff to load buses via the backdoor with mixed results. Subsequent rounds of service changes have kicked more and more buses out of the tunnel and onto city streets, but buses may hang on until the early 2020s before being fully eliminated from the tunnel. In the meantime, light rail service in the tunnel is regularly delayed by bus operations.

Sound Transit likely doesn’t want to unnecessarily recreate such poor service delivery. But if buses are denied access to a transit tunnel, we’d have to assess how rapid BRT to West Seattle could effectively work through Downtown Seattle.

Growth Potential

Much of West Seattle’s light rail long term viability hinges on growth. Skeptics say West Seattle simply won’t grow enough to justify light rail investment. Underlying this is the assumption homeowners and neighborhood activists will block changes in zoning and impede development. They might be right, but the irony is that the BRT crowd is perfectly willing to talk politics when it supports their point on land use (i.e., NIMBYism will prevent West Seattle from ever growing into a community large enough to support light rail). On transportation, however, they don’t want politics to factor into a sober assessment of transit quality. They say BRT could serve more of West Seattle and Delridge with one seat rides for much cheaper, so we should just dismiss some people’s stated preference for rail as a frivolity. At least in Sound Transit’s survey, West Seattle elevated light rail had strong support, getting more votes than any other listed project. If we think we can overcome rail preference to sell BRT to West Seattle, I expect we might be able to sell them on zoning changes too.

Current Density

In 2010, the US Census Bureau found that the wider West Seattle community had a population just shy of 83,000; Southwest with 48,008 and Delridge with 34,904.

This is how the City of Seattle roughly delineates its neighborhood communities for statistical purposes, although the 2010 census data may represent a slightly different region. (City of Seattle)
This is how the City of Seattle roughly delineates its neighborhood communities for statistical purposes, although the 2010 census data may represent a slightly different region. (City of Seattle)

West Seattle and Delridge are growing steadily, although nowhere near as rapidly as the incredible rates achieved in Downtown and Lake Union. From 2000 to 2010, West Seattle grew by 4.6% while Delridge grew by 6%. Recent data from The Seattle Times, showed continuing growth concentrated most heavily around Avalon and Alaska Junction. Moreover, a quick glance at Seattle in Progress confirms that more than a dozen big projects are on the way.

Chad Newton at Build The City blog made this nifty density map based on 2010 census data. As you can see, West Seattle has only a few sections in the orange (10,000 to 25,000) density level. (Chad Newton)
Chad Newton at Build The City blog made this nifty density map based on 2010 census data. As you can see, West Seattle has only a few sections in the orange (10,000 to 25,000) density level. (Chad Newton)

BRT proponents say that even if West Seattle grows significantly, its transit demand still won’t catch up to denser areas in the central core of the city or the dense urban swath found from Ballard to the University District. That may be, but this doesn’t have to be an either/or proposition.

Hypothetically, West Seattle and Ballard both could get light rail. We could even build the Metro 8 Subway if we lobbied Sound Transit hard enough. Sound Transit could also help Metro upgrade its most successful RapidRide line — the E Line — to as close to full BRT as possible. The E Line (Aurora Village) reached 15,800 weekday rides in 2015 and leads the RapidRide pack by far; this seems an obvious place to invest further. Adding more BRT lines than just a hypothetical West Seattle line would also avoid accusations of favoritism, and it’d spread ST3 benefits across a wider area.

Maybe BRT will ultimately be the best solution for the West Seattle peninsula, too. But at this juncture, we need to study both light rail and BRT options further to evaluate their costs and benefits.

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Doug Trumm is The Urbanist's Executive Director. An Urbanist writer since 2015, he dreams of pedestrianizing streets, blanketing the city in bus lanes, and unleashing a mass timber building spree to end the affordable housing shortage and avert our coming climate catastrophe. He graduated from the Evans School of Public Policy and Governance at the University of Washington. He lives in East Fremont and loves to explore the city on his bike.


  1. Excellent article (I just discovered it). I completely agree. As someone who supports BRT, and has come up with a proposal (cited in your article) I think what we need to do is study this more.

    Sound Transit did study BRT, but they made certain assumptions. They left out any major infrastructure improvement. Those pushing for BRT have proposed some extensive fixes. These aren’t cheap, but they aren’t as expensive as light rail.

    Since Sound Transit proposed nothing in the way of infrastructure improvements, the results for BRT were as expected — disappointing. Without improvements to travel times, you get something similar to what we have now (RapidRide).

    I would split the studies. First I would assume that a bus tunnel could be built, and that fixes to the West Seattle freeway (such as the one I proposed as well as this) could be made. That means that you can assume that a bus will travel roughly as fast as a train. I would then study the potential corridors. How many buses can go into the tunnel at once? You can work from there. The folks who put together the proposal for the WSTT came up with a set of buses they think can easily fit in the tunnel. It is possible that you could get more. Not only from West Seattle, but from SR 99/509. Then figure out how many transit minutes are saved. Not just added ridership, but how many potential trips (whether they are taken by transit or not) would benefit if the rider took transit, and how much time would be saved. Include the time saved by buses that would not be BRT, and thus would not use the tunnel (e. g. the 50). Take those numbers and compare them to the light rail option. This would involve fairly extensive modeling (more extensive than has been done before) but we are talking about spending a relatively small amount of money (a few million) to determine how to spend a huge amount (billions). Measure twice, cut once.

    But that is just for the ridership estimates. You would also have to do engineering studies. The tunnel is fairly straightforward, as much of the work has already been done. The buses themselves are not that expensive (relative to everything else). This just leaves the work on the West Seattle freeway, its on-ramps, and the Spokane Street Viaduct. How much would that cost? Could it actually produce the kind of speed suggested?

    I would be willing to bet that you would find that not only does the BRT system save money, but it saves more people more time. Just the WSTT by itself is probably a net winner. While commuter based traffic is terrible on the West Seattle freeway every work day, it isn’t as bad as the slog through downtown. It is also only a problem heading to downtown in the morning. This means that a very high percentage of the trips (evening, mid-day) would gain little from a train versus a bus tunnel. Quite the opposite. Anyone coming from South Seattle College or Alki would have a direct trip to downtown with a bus as opposed to being asked to make a transfer. Most of the day that would be faster (assuming the WSTT was built). Eliminate the outbound morning traffic on the West Seattle freeway, and you make the bus option faster for just about everyone.

  2. “The [light rail] ridership numbers seem inflated.”
    That’s a fairly bold statement with no further explanation. What makes you think that?

    Also, your addition of the 40,000 riders on Delridge to the 50,000 from West Seattle excludes a consideration of bus-rail integration that ST would have included in their ridership estimates. The project sheet for C-03a notes that there would be a transfer facility at Delridge, so wouldn’t Delridge’s ridership be at least partially included on the Junction line?

    • The numbers seem inflated because the lines and stations didn’t change as far I can tell from the more detailed corridor study to the corridor summary but the ridership went up by about 20,000 for each option. Junction went from a high-end of 29,000 to 50,000 and Delridge went from 22,000 to 40,000. It’s possible they factored in the new downtown transit tunnel for the first time like they did for the Ballard-Downtown Line but that isn’t specified.

      Another way to see how optimistic those numbers are is to look at current bus ridership. The RapidRide C got 8,300 average weekday ridership this year, which is a long way from 50,000. The 120 bus got ridership of 9,200 but you can’t assume a majority will want to get off the bus and on the light rail at the Delridge transfer station since the transfer penalty may actually make their trip longer.

      That said, the projections could ultimately be right. It’s possible good LRT service would lead to a major mode shift in West Seattle. Currently a high percentage of West Seattleites drive but that percentage much be much lower in 2040. That’s why I’m still not ruling out investing billions in LRT.

      You are absolutely right about Delridge and Junction. Junction numbers likely include transfers from the Delridge transfer station. You wouldn’t just add 40,000 and 50,000 together. One alternative would be adding the low-end estimates together: 34,000 + 39,000 = 73,000. Really though you’d need another study of the branching idea to get a good estimate. We could expect much higher ridership from full Delridge LRT than we can from a measly transfer station near the freeway with the inherent transfer penalty.

      • If light rail to West Seattle is constructed, the C reverts to local service (no more red buses) and the 120 ends at Spokane Street. Running buses from West Seattle to downtown will be duplicative, and the buses will be slower than rail even off-peak post viaduct demolition.

        • Yeah the viaduct demolition might throw another wrench in bus transit to West Seattle. Would the same be true of Delridge? At 10 minute headways the transfer penalty would average something like 5 minutes I guess. Would the light rail be 5 minutes faster from Delridge than a bus off peak? Ross is right to look at these things critically. The tranfer penalty is partially why I proposed a branching line allowing one seat rides from the Delridge corrdior. Ultimately I’m optimistic about the long-term viability of well designed West Seattle LRT granted that it’s a lower priority for me than other lines such as a Ballard-UW or the Metro 8 Subway (admitting the 8’s been completely overlooked so far).

        • Also Chad excellent work on the density map. It really helps put this in perspective. Thanks for delving though the census data and creating it.

    • Also Chad excellent work on the density map. It really helps put this in perspective. Thanks for delving though the census data and creating it.

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