Photo by Oran

One of the minor disappointments as Central Link took shape was the lack of center platforms.  Of 13 stations, only Stadium, Beacon Hill, Rainier Beach, and Seatac have these center platforms.  The four DSTT stations share right-of-way with buses and so in effect must have outer platforms.

Center platforms are highly desirable at termini and at train-to-train transfer points, for obvious reasons.  As the only currently planned transfer point, I’m hopeful that Chinatown/ID Station will get a center platform between now and 2020 to facilitate transfers from South to East and vice versa.

More generally, though, it seems prudent to construct these wherever possible because you never know where a terminus or transfer might occur someday.  Rainier Beach is equipped to be a turnaround for trains because it has a switchover, so it’s fortunate it has a center platform.  To speculate a little more wildly, in the distant future Link may more or less follow the RapidRide F Line from Burien to Southcenter.  Tukwila Station would be an obvious place to switch between the lines.  Unfortunately, for no apparent reason this was built as an outer platform station.

The other bonus of center platforms is that it makes it easy to double back if you overshoot your stop.  Fortunately, Capitol Hill appears to be center-platform.  Here’s hoping Sound Transit finds more opportunities to use this approach.

76 Replies to “Center Platforms”

    1. In one respect, center platforms should be cheaper. The number of stairs, escalators and elevators to access the platform at an elevated or underground station should be reduced.

    2. There can be additional costs associated with center platforms. As the tracks enter and leave the station, they are more spread apart – by about 30 feet. This usually means more right-of-way is needed for a longer distance on both ends of the station, with more impacts to adjacent properties and roadways and potentially more property acquisition. For elevated structures this could mean separate structures for each track for a distance, like you see at SeaTac/Airport Station.

  1. The lack of center platforms in the DSTT is a major failure of the original Metro tunnel designers to think beyond their narrow, roads oriented paradigm.

    Yes, buses (almost) always have doors only on the RHS. And, yes, cars/buses in North America at least travel on the RHS of the road. So if you stick to that narrow line of thought then center platforms are not possible with a bus tunnel.

    But the drivers operating in the DSTT are professionals only and the tunnel is a managed operating environment, and it was always intended for conversion to rail anyhow. There is no reason that the buses couldn’t stop at each end of the tunnel and then switch lanes — with NB buses traveling on the LHS and vice versa.

    This would allow the use of center platforms which in turn would reduce the footprint of the station and reduce overall costs (smaller stations with only one set of escalators/elevators/etc per platform). All that is lost is the center passing lane, but this doesn’t get used much anyhow and is of dubious value.

    Consider it an opportunity missed.

      1. Apropos of designers not thinking beyond a paradigm, the Fed Way TC has something I’ve always considered an oddity that could have been avoided by better design: motorists approaching from the south on 23rd Ave are not allowed to turn into the east entrance, but have to drive all the way around the TC to enter on the west.

        It seems that this problem could have been avoided by designing the TC with a 5-way intersection, where two of the five legs are the transit and commuter entrance/exits, and the other three legs are the existing streets (23rd Ave to the north and south, and 317th St to the east). It’s as though the whole thing were designed by somebody from out of state who was unaware of Seattle’s tradition of 5-way intersections.

        Sorry if this is OT.

    1. I asked about center platforms in the DSTT three weeks ago and was told that “Buses used to pass pretty often in the tunnel”, so the center lane apparently wasn’t considered of dubious value when the tunnel was designed.

      1. It’s not used that often, and will never be used once the DSTT goes over to 100% rail. It’s nothing more than dead space — very expensive dead space.

    2. Well, since these are big downtown stations, it’s really nice to have two seperate platforms, each geographically orientated for specific routes. Having one center platform could lead to overcrowding and pedestrian congestion. Considering how crowded the DSTT platforms can get, its nice that there aren’t 4 sets of buses/trains serving one big platform. Imagine how wild it’s going to get down there when North Link opens.

      Also, its much easier to bore the tunnels under the city streets as nearly-arrow straight as possible.

    3. Yes, with 20/20 hindsight we now know the center lane in the DSTT wasn’t needed. Trouble is, we didn’t know that when the tunnel was being designed, did we?

      1. Transit vehicles were also high floor only at the time when the DSTT was being designed. There was discussion about using high platforms in the DSTT with a special doors on the left side of tunnel coaches. It was not an easy decision to stay with low platforms. But it would have made the Link Rail DSTT retrofit and the tunnel bus replacement much more complicated if high platforms were built.

      2. What do you mean the center lane wasn’t needed? Before the tunnel retrofit, the Breda’s where allowed to pass in the station, with each station having a passing wire as the Breda’s were electric. This was great if a coach had a wheelchair or it broke down for some reason.

        Now we aren’t allowed to pass for two reasons. The trains. And the other reson, even before the trains. We are trained to operate the coach within a certain distance of the platform, about 6 inches. Because the curbs are high, the bus can be damaged if we touch the platform. When passing a coach, you have to turn out into the center lane. By doing this from the position of 6 inches from the curb, you can easily touch the platform with the coach because of tail swing.

        The center lane is needed to pass a coach or train that may be disabled in the station, but only with permission form Link Control. Also, if a center platform existed, the ablility to access the tube (oppostie direction) if the tube in your direction was blocked by a bus or train. When we tunnel trained, this was presented as an option that obviously only the buses could do, under direction of Link control and supervisors, if a tube segment was blocked.

        So yes, the the center lane was needed and was often used prior to the ST retrofit, but is still needed when the situation arrises, that a bus or train becomes disabled.

    1. If they did not want to spend much money, they could put a platform in the currently empty center area just for transferring.

      1. Good idea. Still, they would need some stairs and an elevator in case people got off on the wrong side.

      2. Why not just let pax walk from one side to the other? Forget the expensive elevators/escalators. Pax cross the tracks at grade in many of the stations anyways.

      3. You probably have to have a permanent ADA way off in case the system shuts down in an emergency.

      4. Also, people are not supposed to cross anywhere besides marked crossing locations on MLK and in SoDo. Once buses leave the DSTT, it is planned that Link trains will move much faster in there. There are limited lines of sight from the tubes leading from Pioneer Square to IDS. Safety and/or speed would be reduced in the tunnel if there was a crossing between platforms in the DSTT.

      5. like the Boston Red Line @ Park Street- has platforms in center and on the external sides fo both tracks.

  2. Central platforms are nice when transferring from train to train, but side platforms work well to for transferring from a train to a bus.

    1. Center platforms wouldn’t work any differently for transferring from a train to a bus. Sure, you might have to *gasp* cross the platform.

      1. The center platform wouldn’t be helpful if you wanted to cross from a northbound Link train to an eastbound bus. You could get off on the center platform but then the bus would pull up beside you and you’d have no way of getting on.

  3. the likelihood of a center platform at any of the DSTT stations will be slim to none for a simple reason – If a train were to break down at any of the given stations (IDS for example) a truck would need to either do the following

    A: Be dispatched from the O&M to IDS. The only way to get into IDS with a truck would be to temporarily shut down the Southbound traffic while the Northbound train is rescued. It’ll

    B: Be dispatched from Convention Place to the train and pulled to Pine Street then backed to the O&M causing a huge disruption.

    C: Hold all NB trains at SODO station to allow the tow truck to recuse the train and cross over at Stadium Station…

    Whichever option, it will be at least a 20-60 minute delay to services. Now if and when we get up to 4 car trains, that may change things but since I have yet to see a 4 car train in the tunnel to figure out if a truck could even get in between the ends, is hard to say.

    Right now though, I highly doubt we’ll ever see center platforms at any of the DSTT

    1. Plus the conversion costs would be high, not to mention the disruption. This is something cities all over the world have lived with, and we should too. Use the money to expand service not redesign stations, please.

    2. One advantage with multiple powered cars is that the other functioning cars can push/pull out a non-working car. Other transit agencies do this and put the train out of service until they can get to a yard. The odds of all 2/3/4 LRV’s crapping out at once is rather low so a truck might not even be necessary.

    3. Those are fair points, but why is the DSTT any different than say, Beacon Hill or Seatac station? Neither of these are truck-accessible …

    4. if a LRV gets disabled … they would just couple a working one to the end of the disabled car and tow the whole bunch out of the way … of course with 2+ cars … the likelyhood that all fail is small (that would be a system outage affecting everything) …

      1. Yeah, that kind of thing can happen to Beacon Hill as well, so I don’t see it as a big requirement for a vehicle to get around a train at those platforms. We’ll have to have the buses out first, though.

  4. Sorry for a double post, but it might be a good idea to put a track down the middle lane and turn it into a crossover with room to tuck a 1-car train in the middle.

  5. Capitol Hill, UW, Brooklyn, Roosevelt, and Northgate will be center-platform stations.

    In the case of underground stations, center platforms are MUCH cheaper. The station box doesn’t need to be as wide. For example: 2x 10′ wide tracks and a 15′ wide platform is narrower than 2x 10′ wide platforms and 2x 10′ wide tracks. That addtional 5′ can cost $10 million.

    I really fail to see how Tukwila’s platform position matters. Its forever an intermediate stop. Speculating, it probably has outside platforms due to the heavy grade and crossover coming up from the east. The scissor crossover has to be on fairly level ground and there isn’t a huge amount of room to have the two tracks zip apart for a center platform. Note how much distance it takes to go from double trackes though the #10 scissor crossover at SeaTac to the platform.

    1. Re: Tukwila forever an intermediate stop.

      I believe ST2 includes a planning study for a Burien-Renton line. How this would perform remains to be seen, but I presume any such line would include some kind of transfer at TIB and the Tukwila Sounder station.

      1. if they do this … they would just join the new elevated ROW to the existing one. if you want to change trains you’d have to go down and back up onto the other platform

  6. I don’t foresee the West-Seattle/Burien line or the Renton/Tukwila line stopping at Tukwila International Boulevard Station. I would think they would all stop at Seatac/Airport Station instead, since, unlike TIBS, it is a major regional destination.

    1. No, all the planning centers around Burien-Renton intersecting the main line at Tukwila. If you look at a map you will see that SeaTac station would require a considerable jog south, which would be more expensive and would slow travel times from Burien or Renton to downtown. In addition, the new routing of MT 140 (and the future routing of RapidRide F), which are the lines that Burien-Renton link would replace, stops at Tukwila, not SeaTac.

    2. Stopping at Sea-Tac would be nice, but either a detour or a bored tunnel through all that runway fill (Do’h! Shoulda thought of that when they dumped it all there…) would be necessary.

  7. Center platforms are even more important for streetcar lines. When streetcars use the outer lane, they share right-of-way with emergency vehicles. When an emergency vehicle stops in the emergency zone, the streetcar is blocked.

  8. Center platforms on surface streets like MLK consume more real estate, due to having to widen the track for a considerable distance on either side of each station. I remember riding the Blue Line in LA which is all center platforms. Big curves on each end of each station. Track engineers like to build straight track; simpler and less wear and tear on the works.

  9. Most Paris Metro stops are side platforms, from the very old to the very new. Someone pointed out something about track engineering, and that’s probably it. The sections where the tracks diverge for a center stop have to be relatively sharply curved, or else the tunneling would require more space.

    This probably works better with crowd control, and trains can cover track faster without navigating curves. In rush hour, trains may be a minute apart, and platforms chocked full of people. There are also no co-linear transfers in Paris. Each line is on a separate track. For these types of transfers, platforms can be built parallel, so in one transfer direction, one can simply walk across the platform to another line.

    For our system, it may be nice to have a middle transfer at ID station. Someone suggested that we just build a center transfer platform and leave the other side platforms.

    1. When East Link line eventually opens, is it going to have its own dedicated track, separate from the Central Link in the DSTT? If so, this means there would need to be build another platform dedicated for East Link only at the Chinatown station. Then center platforms for the both East Link line and Central Link line would be easier for transfers to SeaTac station from the eastside.

      1. You’ve got to be kidding… Between the buses, Central link trains, and East Link Trains, it will be utter chaos! This is going to result in frequent collisions and delays!

        When will Sound Transit get a ‘friggin brain?!

      2. There won’t be busses in the DSTT by the time East Link opens. Central Link and East Link trains will merge at the ID Station (as the trains and busses do now) and probably at Northgate Station (maybe further north).

  10. Just don’t pretend Center Platforms with streetcar lines is a good idea. Many people won’t like waiting in the middle of traffic. Some will opt to wait on the sidewalk until the streetcar is spotted and then risk dodging through traffic to reach the platform. Sorry to have to be contrary, but someone has to consider this reality, you know, just trying to prevent pedestrian fatalities.

    1. Some will opt to wait on the sidewalk until the streetcar is spotted and then risk dodging through traffic to reach the platform.

      I don’t think you need to worry about Trolley Dodgers much in a American League city ;-)

    2. I use the center platform at Yale and Fairview all the time to catch the South Lake Union Streetcar. Never once have I seen someone wait on the sidewalk instead of the platform. The platform is well protected from traffic and probably safer than the bus stops in the curb lane. Traffic speeds past the sidewalk in the curb lane just as fast as it speeds past the center platform, so I don’t really see a difference. And the center platform doesn’t get splashed from cars and buses driving though the pooled water in the gutter like the bus stops on Fairview do.

      In Berlin almost all of the streetcar lines are center running. In a lot of locations they have signals above the adjacent traffic lanes that stop oncoming traffic when the streetcar is stopped. The streetcar can then unload passengers right into the street. I’ve yet to hear any stories of mass pedestrian carnage in Berlin, but maybe they’re just smarter than us.

    3. Wells, you’d really have to demonstrate that as a problem. There are a lot of benefits to center platforms for streetcars – like reducing the impact on bicyclists.

      1. Personally its a little unnerving standing in the middle of a 5-lane road. Portland has a couple center-road streetcar stations and drivers shoot by. The north end SLUT station does have that nice steel fence.

        How about the bicyclists reduce their impact on streetcars? Do 1,100 bicyclists use Westlake Ave daily? I doubt it. Or my bus? Or grow a pair?

  11. there is no reason why they couldn’t put in center platforms at all the DSTT stations. I think the only ones that would actually require major rejiggering would be the international district station (they’d have to cut out new elevator and stairs/escalator openings to the courtyard above and Westlake … where the Mezzanine level sits above the center of the tunnel … making access for stairs and escalators problematic.

    Pioneer SQ and University … they would just have to duplicate what they have done for the side platforms … with the addition of elevators

  12. Center platforms generally require more right-of-way, as the track spacing must be much wider as trains enter and exit the station. Also, while they facilitate X-platform transfer, they also can create more conflict as passengers waiting for trains in each direction and entering/exiting trains in opposite directions are in the same space. I like them for transfers when two or more line share the same tracks, but for a single line, side platforms are much cleaner for operations.

    1. Dude,

      What you’re saying is true of surface and elevated stations only. Bored tunnels are actually more stable if they’re separated by a couple of dozen feet. So it makes sense to use center platforms with them for the health of the tunnels between stations as well as for the lesser volume of earth to be mined for the station.

  13. I’m going to have to say that I really don’t see this as a big deal. There’s pros and cons about both, and the decision between the two is based on the environmental context of the station location more than anything else.

  14. If the U-Link and North Link station cross-section plans are representative those tunnel stations will all be center platform, which makes sense with the above-stated cost benefits for tunnel stations.

  15. When two light-rail lines intersect, there should be TWO stations. Once there is a vast network of subway/light-rail, the trains will be running too frequently to be sharing stations with other lines.

    AND… Get rid of the buses in the DSTT! Buses and Trains don’t mix!

    1. The busses will go away eventually. By U-Link will make the 71-74 mostly redundant in the tunnel, expanding to Northgate will get rid of 41. East Link will replace the 550. Those make up the majority of busses going through the tunnel.

      Having the line both run through the tunnel won’t be a disadvantage, it will enable a reduction of headways from Northgate to ID Station, maximizing capacity and user efficiency.

    2. I think trains and buses mix fine, except for the occasionally breakdown. And I know it can be a little slower at peak hours, but so many of us Metro drivers love it the tunnel. Delays in the tunnel aren’t too bad. I will be sad in 2016 when all tunnel routes will be back on the surface.

      Also, if you don’t like buses in the tunnel now, I hate to break the news to you, but more routes are going into the tunnel in February. Now that the 174 and soon to be 194 are gone, a little space has become avalible. So in February Shake-up, Routes: 76, 77, 216, 218 and 316 will be added.

      Here’s how I see it.
      In the PM Peak 3-7pm…..
      174 in the past operated :30min service…..8 N/B trips, 8 S/B trips
      194 currently operates at PM Peak………..15 N/B trips, 9 S/B trips.
      So combined deletion of 174/194 during PM peak is 23 N/B trips and 17 S/B trips.

      In February in the PM Peak 3-7pm(I’m going by current service levels on these routes)
      76 operates 9 trips (N/B)
      77 operates 9 trips (N/B)
      316 operates 8 trips (N/B)
      216 operates 6 trips (S/B)
      218 operates 14 trips (S/B)
      Total of 26 N/B trips, 20 S/B trips

      So over the length of the PM Peak (4 hrs) that is only 3 extra trips in each direction. Should not be an issue. So I’m glad they are putting more routes in the tunnel replace the 174/194.

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