In a few days I’ll be interviewing Darlene Pahlman, senior engineer on SDOT’s MLK Signaling project. I’ll be talking through how signal priority is working for Link. If you have anything you’d like me to ask her, please offer it in the comments.

81 Replies to “Your MLK Questions!”

  1. My question is simple: Why do Link trains ever have to wait at a traffic signal, and what can we do to avoid these delays, both now and in a future with more new development and more frequent Link service?

    1. I have the same question – I’ve been on Link in the Rainier Valley on a few trains which have had to stop at some seemingly minor cross streets. I thought signal timing was supposed to take care of this. How to cars sometimes get priority?

      1. Agreed…it is so frustrating to be held up at a small intersection. I thought that the signal priority was supposed to make the at grade portion effectively work like grade separated without the actual barriers. It’s crap to make a Link train wait for one car making a left turn from some side street.

        Every time Link stops at a light midway between stations, I cringe. That is not how a world class rapid transit system should work. It turns the train into a bus for the duration of the delay.

  2. Is there any way, say if we put full fledged railroad crossing infrastructure at intersections and/or fenced off the line, that we could start running trains at 55mph on MLK way?

    1. Sound Transit has an official answer for this. They wanted the Link along MLK to be open and inviting. They and the community did not want a freight rail corridor running down the middle of the street as they have along SODO.

      1. Link doesn’t carry freight; nor does it run in the middle of the street in SoDo. The historic railway down the middle of Rainier did carry freight, however.

    2. If you raise the speed limit on MLK to 55 mph, the trains could travel that fast as well. Not that I’m recommending this.

      1. They need to put it underground like any other city worldwide would do. Having it underground, the noise is trapped, and it can travel twice the speed.

  3. Back in mid-November I spent some time taking photos at the intersection of MLK & South Dakota and observed that after a pedestrian signal request was triggered to cross MLK, there were delays of 5 to 10 minutes before the signal changed to permit east/west traffic on South Dakota and a pedestrian to cross MLK. Others I’ve talked to have told similar stories of long delays waiting for pedestrian phases at crossings of MLK away from the stations. What causes these delays, and is there a way to resolve them?

  4. I’ll repost my questions from this old post here, since I can’t remember those questions ever being answered.

    What is the cycle length on the signals?
    What is the average or typical coordinated phase length?

    Also would be interested to hear answers to Adam’s questions as well:

    – What is the maximum green extension and early green the system will give.
    – Is there TSP in both directions doing peak times. Only one? Or does the peak direction get longer green extension/early green than the off peak direction?
    – Are their a maximum number of priority request that will be granted per signal cycle/hour/etc
    – Does the cross street function class, volume or cycle failure, affect approval of priority request.
    – Are requests sent to a central control system or is it handled in the field. There is fiber along the corridor correct?
    – What is the tracking technology? Is it built into to the rail system or is it GPS based?
    – How will the system affect the side street pedestrian green.

  5. I rode Link back from the airport around 9PM recently and noticed that it stopped several times at what I assume were streetlights, something that didn’t happen when I have taken it during the daytime. Do they stop signal preemption at night? Why?

    1. I believe TSP for Link has longer early/extended greens in the peak in the peak periods. Given that there is less auto congestion during the off-peak periods, and therefore TSP impacts fewer autos, why are trains forced to stop more frequenty?

  6. I want this question out there as much as possible: Will there ever be a stop at ether Orcas or Graham. What can we do to get that to happen?

  7. This question is not about MLK Jr Way, but it is related.

    I have seen the Link crossing gates across Lander Street blocking traffic across the SODO bus lanes/Link tracks for over two minutes at a time, when two Link trains crossed Lander from opposite directions within a minute or so of each other. Just when the gates would be opening after the first train crossed Lander, the second train came along from the opposite direction, so the gates just remained down for both trains, which, in at least one case, was over two minutes straight.

    This caused east-bound traffic on Lander to back up a full block into the intersection of 4th and Lander.

    I find this unacceptable. Can something be done to make sure that those crossing gates never stay down for more than about one minute at a time, and there is at least two minutes of the gates being up between times when they are lowered?

    1. Martin,

      Thanks for doing this one. Friend of mine is a LINK motorman- he’ll comment when he gets off shift tonight. Evidently there’s a lot involved in MLK operations- both the signal setup and working with it.

      Interview and comments should be really valuable.

      Mark Dublin

    2. there is at least two minutes of the gates being up between times when they are lowered?

      But then the second Link train would have to wait two minutes… and the train probably has more people on it than people that would be on Lander. Also, 4th is only about 300 feet from the tracks, so it’s really not that far.

      1. 300 feet is one city block. You are correct. The Link tracks, and SODO bus lanes are where 5th Ave would be, whick is one block east of 4th Ave. That is why traffic backs up to 4th Ave, so people wanting to turn onto Lander from 4th are not able to do so. So, in reality, traffic is backed up further than just to the intersection of 4th and Lander — it backs up in both directions on Lander also, in the lanes where people want to turn east onto Lander.

        Why don’t they schedule the trains so that this does not happen?

      2. Trains have priority over auto traffic there. It may have been different in the 20th Century, but for the 21st Century, at that and many other locations in coming years, cars will be playing “second fiddle” to trains, and none too soon. Some of us waited 4 decades for a train – drivers can certainly wait 2 minutes for the train to clear the crossing.

      3. Yup — a two minute wait there occasionally is really no big deal at all, unlike the waits further west on Lander for freight trains that can take 10 minutes to go by! I have to drive east on Lander relatively often and I haven’t found Link delays to be any particular big deal.

      4. I keep hearing rumors there might eventually be a grade separation done on Lander for the BNSF tracks.

      7. Norman said: “But 2 minutes is too long for a light rail train to wait occasionally? Why is that?”

        Because the train has the right kind of people on it and the cars, well, not so much.

        There, someone said it to your face.

      8. Not to mention that many times transfers are necessary when taking public transit so it is very important trains be on time. The nature of auto transport is much more fluid.

      9. So people in cars and buses are never trying to make it somewhere “on time”? Their time is not important, compared to the VIP’s on light rail trains?

        Anandakos: I assume you were being sarcastic. If not, please let me know.

      11. Not being sarcastic at all. I drive sometimes, but I do my best to let buses and other public transit vehicles have absolute right of way.

        I’m expect you’ve conveniently overlooked the yield signs painted on all Washington State transit vehicles.

      12. Apparently you’ve never been stuck waiting in SoDo for a freight train to pass through. One or two minutes to wait there is NOTHING.

      13. I have been stuck waiting for a freight train. That was before they built the Edgar Martinez Way overpass over all the railroad tracks. Now I use that overpass always, and never get stuck waiting for a freight train.

        You should try that overpass. Works every time.

  8. Similar to some of DJStorky’s, as ridership increases can we expect to see increases in the level of priority/preemption such as increase in early/extended green times? Will this be adjusted in the future or have does LINK currently operate at the planned level of priority?

  9. I would like to know if maintaining consitent headways through the signals has been a challenge for ST? Also does getting the timing right have anything to do with why they haven’t turned on realtime arrival?

    It seems to me that they have the ability to turn on and display realtime arrival but have been reluctant to do so. My theory is that they want the trains to be running as on-time as possible before displaying the realtime arrival info to the public.

  10. Why are there some cycles where pedestrians are not allowed to cross? At Alaska, after a train has crossed, there is an immediate change for the traffic on Alaska to go through, but pedestrians not given walk signals until the next full cycle.

    My general frustration, as expressed by those above, is why trains would have to wait at all. If we’re going to have 4-5 minute cycles, it had better be because trains are zipping on by. They aren’t.

    1. My question is related … Would it be possible to have a quick pedestrian phase for crossing MLK immediately before and after a train passes through a station? When the “train priority cycle” is triggered, there would also be quick red light phases along MLK between the longer “train passing through” green phase.

      I have had interminable waits to cross MLK to access a station, and while waiting a train approached. If I hadn’t jaywalked, I would have been waiting another 10-15 minutes to take the next train.

  11. Can there be a signal indication to the train operator upon arriving at stations on MLK when the signal for the intersection ahead has or is about to “time out”? This would allow us to wait to request the train signal until we knew the train would not be delayed.

    Would “demand signal phasing” (is this the proper term?) (currently used after midnight and all day on Sundays) during early evenings (maybe mid day and Saturdays) ease the complaints of perceived long waits by auto traffic? Most of the close calls I experience are cars that turn against a signal when there is light automobile traffic – presumably out of frustration.

    What if anything are we as train operators doing that exacerbate signal issues? What could we do to minimize signal priority loss and train delays?

  12. Fun technical questions:

    This stems from me noticing that the signals on the MLK crossovers are (at least in the freight world) absolute signals and are set well in advanced of others along the corridor. So…

    Can the dispatcher manually control each individual intermediate/intersection Link signal at each street crossing/intersection or is it all automated?

    Are the MLK intermediate/intersection signals visible to dispatchers or are they similar to freight rail signal systems where intermediate signals between absolute signals are invisible to dispatch and their control?

    Since the only absolute signals appear to be at MTB, Othello, and Rainier crossovers, how does this effect headways along MLK? Or how many blocks of separation have to be between trains on MLK?

    Have pedestrians running across the trackway been an issue?

  13. (1) The signal at Webster/Renton and MLK appears to be broken. Well at least I often sit at the light waiting to turn for 5 minutes and once sat there for 7 minutes. I have begun timing this phenomenon. It occurs both when traffic on MLK is heavy and light.
    (2) When will the stations start announcing the time of the next train. You had previously reported Dick Burkhart’s report from ST that this would start in December with the Airport Link. Thoughts?

    1. On Sunday an announcement (loud speaker) was made at the Pioneer Square station to the effect that the next northbound train would “arrive in two minutes”. Only thing is that the train arrived mere seconds after this announcement was made :(

      1. Yesterday evening at University Street there was an announcement that the train would be arriving in 2 minutes, but it came 5 minutes later. This morning however, at Mt Baker I heard “The train is now arriving, please stay behind the yellow textured strip.”, and it did indeed arrive about 20 seconds later.

  14. Yes to the traffic light holdup question and the long crosswalk wait time question. I’ve experienced both.

    My understanding is that Link gets green lights only within a narrow time window, and if it’s a minute delayed or the trains around it have reached a certain pattern, it misses the window and gets red lights.

  15. Here’s my question. Please explain and clarify the differences for the following terms that people seem to be confused with:

    • signal priority
    • signal preemption
    • signal coordination

    I may already know the answer to this but I want their interpretation.

  16. Question: Is there an agreement in place that limits the headways of trains, or the level of signal priority given for future service along SODO or MLK?
    Note: Trains are only 2 cars long, and 7-8 minutes apart. ST2 and beyond calls for twice as long trains, running at least twice as frequently.
    Will the trains still be given priority, even if intersections go to LOS E or F?

    1. As a follow up, you might pose the question of this:
      What’s to keep a ‘Rogue’ Mayor and Council from ordering signal priority turned off, to relieve traffic congestion around light rail lines?
      Did ST get the ROW priority ‘etched in stone’?

    2. The answer to this could transfer to thinking about Bellevue at-grade options, which isn’t a far fetched conclusion.

    3. I think the standard is that at-grade rail should never have headways under six minutes, or cross traffic would be seriously messed up. As I posted above, even with suupposedly 7.5-minute headways, there are fairly often two trains going through an intersection within one minute of each other (in opposite directions), which already causes big backups and delays for crossing traffic on Lander Street during peak traffic hours.

      This likely also happens at Holgate and Royal Brougham Way crossings, but I have not witnessed it at those intersections. I have heard that those intersections can have very bad backups due to light rail trains before and after Mariners home games when many vehicles are trying to use those two streets to get to or from an M’s game. But I can’t say I have actually seen that for myself, since I avoid that area whenever there is an M’s home game. This baseball season, I think I will wander around down there before and after some M’s games just to see if Link trains really cause traffic problems on Holgate and Royal Brougham Way, or not.

      4. I’ve noticed that the delay to traffic in SODO is longer than along MLK. I attribute this to the time required to lower, then raise the crossing arms. Also note that at the freight crossing when the lights stop flashing and the arms go up cars begin crossing. At the busway, the flashing lights are also coordinated with the traffic light which seems to stay red after the crossing lights stop flashing.

      5. The lights sometime stay red to allow buses on the busway to move through the intersection. Buses have always had signal priority along the busway and were impacting cross traffic a long time before Link came along.

      6. The bad traffic on Royal Brougham for the last year was more likely due to construction of the new bridges than Link.

        Also, other cities also have at-grade light rail next to baseball stadiums (Minneapolis [where the new stadium itself is a transit station], Cleveland, Denver), and they seem to deal… we just have more people who like to complain, like you. Also, places like Minneapolis run trains with <3 minute headways after games get out.

  17. Why didn’t you place the light-rail underground with the cut-and-cover tunnel approach? Now, because of ST’s mistake in building it in the CENTER of the raod, the light-rail is traveling MLK Way at half the speed of what it could underground, their have been several injuries, and some fatalities, and the light-rail isn’t even a year old yet. And now you’re trying to do the same thing on the Green Line (East Link) What are you smoking?

    2. “Why didn’t you place the light-rail underground…”

      My arms got tired digging. Sorry, dude; I tried.

  18. When boarding at Columbia City Station I ALWAYS jay walk. There is no way I’m going to chance missing a train just to legally cross two lanes of traffic. In this way I’m glad they placed the tracks in the middle of the street as opposed to placing the tracks on one side and roadway on the other. Depending on which side of the station you were coming from you’d have to cross a 4-5 lane 2-way street.

    Waiting to drive across MLK, particularly near one of the stations, can be frustrating, as can waiting to turn left across MLK. I think the signaling/timing along this corridor must have been incredibly complicated and probably needs fairly regular care and tweaking. I don’t envy the engineers who have to do this. The thing to keep in mind is that the most important thing for this system is safety, so if they err on the side of caution when making timing decisions, it could mean extended waits. The other thing to keep in mind is the trains will have priority. When they have 7 minute headways there is no way they could justify delaying trains 1-2 minutes so a few cars could make it onto the roadway.

    As for the tunneling comments, if they had done a tunnel down this corridor it would have raised costs (both capital and operating) immensely. In the long term, a tunnel would have been preferable. But I don’t think the budget would have been politically palatable. Just my 2 cents.

    1. So, Link trains on MLK Way will likely result in accidents involving people jaywalking to Link stations to catch trains, as well as some accidents involving the trains themselves. Maybe ST will need to have security at every MLK Way Link station to prevent jaywalking, so people don’t get hit by vehicles while illegally crossing that street.

      As far as “justifying” having Link trains stop at red lights along MLK Way, I remember reading that on one street crossing MLK Way along the Link route, there are about 20,000 vehicles per day using that cross street. Since Link is averaging around 20,000 boardings per day, no more than half of which travel along MLK Jr Way, that means that there are only around 10,000 people riding Link trains along MLK Way, both directions combined, each day. Compared to about 30,000 people in vehicles crossing MLK Jr Way each day at that one cross street (at 1.5 people per vehicle, which is probably quite a bit lower than the actual number).

      So, why would you think that a light rail train carrying around 10,000 people per day should take priority at an intersection over a crossing street which carries around 30,000 people per day?

      1. In building Link and in routing it along MLK we as a region and a society decided that, at least along the MLK corridor, we VALUE transit over auto traffic. Compromises had to be made and one of those whether or not we wanted to pay for full grade separation. If there had been some source of funding or the political will to pay for full grade separation we wouldn’t be having this debate.

        Just as cars are supposed to yield to buses re-entering traffic, cars are basically yielding to Link. Do I think improvements are possible along MLK and even SODO? Yes, its possible that wait times could be reduced. I think there are people at SDOT (and Sound Transit) who have studied this problem and are probably aware of the compromises that have been made and are likely willing to re-visit some assumptions and decisions that have been made.

      2. First, your numbers are wrong. The city has traffic volume maps on their website (though they’re outdated, I’m citing more recent 2008 data). The highest volume cross street on MLK at grade segment is S Alaska St by Columbia City station at 15000 average daily vehicles. That section of MLK has 18000 vehicles plus Link’s riders and the No 8 bus’s. Second, you’re not counting MLK vehicles and their occupants which benefit from the signal cascade Link gets. At Othello, MLK volumes increase to 20000 vs cross street’s 8000 and near I-5, 25000. MLK carries far more people than any other cross street.

        So you should reverse your statement to the opposite.

        So far there has only been one incident on MLK involving peds and trains: a person walking into the side of a train. ST’s safety track record has been good so there’s no need to increase security.

      3. I have no problem with MLK having longer green lights than the cross streets. However, if Link trains can’t be timed to hit the lights when they are green for MLK traffic, then keeping lights green for Link trains is not helping all other traffic on MLK Way, which would usually have green lights, anyway. And, don’t forget, that Link trains also hold up many vehicles on MLK Way which are turning left at intersections, across the LINK tracks. So, it is not just the traffic on crossing streets which is backed up by Link trains, it is also the many cars using MLK Way which are turning left at these intersections, and also have to wait for Link trains to get through the intersections before these vehicles can turn left.

        What I object to is interrupting the signal pattern for vehicles on MLK Way to give priority to Link trains. The lights for MLK Way should be timed for vehicles traveling about 30-35 mph, and should not be interrupted for Link trains which have to stop at stations along that street.

        When you alter the timing of lights at intersections, you don’t just hurt traffic on the cross street at that intersection, you also mess up timing of lights at subsequent intersections which are timed to assume the MLK intersection lights work on a set pattern. So that vehicles having to stop at extended red lights when crossing MLK way because of Link, then likely also have to stop at a red light at the next intersction because they were delayed in reaching that intersection by having to wait for Link at MLK Way.

      4. Did you have an actual question for SDOT, Norman? Or are you just using this as your personal soapbox again? I don’t understand why someone who is so anti-transit hangs out on a blog dedicated to transit.

      5. Norman wrote: “What I object to is interrupting the signal pattern for vehicles on MLK Way to give priority to Link trains.”

        Too bad. That ain’t changing.

        (Unless/until many years down the road demand merits tunneling or elevating the whole segment)

      6. Norman, sounds like you would also object to LA Metro Orange Line and Eugene EmX interrupting the signal pattern on their respective streets to give priority to BRT buses, am I correct? Or you just hate Link light rail and want to make it even slower?

        From my driving experience, MLK is already timed for 30-35 mph traffic.

      7. Yes. I do object to traffic lights being put out-of-sync for buses, as well as for trains. Having a significant number of miles of “bus-only” lanes, especially approaching intersections, allows buses to pass lines of cars stopped at red lights, and, that, in my opinion, is enough priority to give to buses.

        For one example, this works quite well very often on 1st Ave heading north, where it crosses Denny Way, and the light for traffic on 1st has a quite short green compared to that for Denny. This results in long lines of vehicles backed up from the Denny intersection on 1st Ave heading north. There is now a “bus-only” far-right lane from 4 to 7 pm (I believe) which allows buses to pass long lines of cars and make it across Denny Way unimpeded. So, buses have a big advantage at intersections such as this without having to mess with the timing of that traffic light.

        I have been in a long line of cars on 1st Ave at this intersection and had buses come screaming past me on my right to cross Denny on a green light, and that is fine with me. This gives buses a big advantage at intersections without messing with synchronization of traffic signals.

      8. By the way, the 1st and Denny transit lane is there because of the far-side bus stop just north of Denny. Due to the operational issues of that bus stop location (curve after a signal), there is only one northbound through lane for cars 24 hours a day. They just remove parking for 3 hours a day… which means that lane wasn’t taken away from cars… it’s just given to buses when bus volumes are high (~1 per minute). Also, the majority of those cars at that signal are waiting to turn west.

      9. Not true. Other than from 4 to 7 pm, cars can use that far right hand lane to cross Denny and continue on 1st Ave N. There are 3 north-bound lanes on 1st Ave approaching that intersection during those 21 hours.

        But the bus-only lane works during peak hours, and allows buses to pass long lines of cars and make it through that intersection without having to wait for more than one green light, which cars often have to do there.

        This sort of thing can be done at a lot of intersections on the RapidRide routes, which will help buses have shorter travel times without slowing down other traffic.

      10. No, Norman, AndrewN’s right. The right curb lane on NB 1st is paid parking. Just check Google Street View, you can see a parking pay station, signs and markings indicating parking in the two blocks of that bus lane before Denny.

      11. I think the Link signals and MLK signals are always timed together. If the train has a proceed signal, the cars on MLK always have a green in the same direction – that’s been my experience driving.

  19. I’m all for improvements in transit/auto/pedestrian/cycle interaction and in particular in minimizing dysfunction and maximizing safety. Truly, I don’t like to see silly situations like a crossing guard being down for 5 minutes because a train is sitting at a nearby station (such as happens in SODO) or it taking 10 minutes to get a walk signal across MLK.

    Beyond the issues of dysfunction and safety (i.e., issues of prioritization) this is a debate on values and what we think the future holds for transportation. My personal opinion (which I will argue but not force on others) is that transit should be a priority. Personal automobiles (even if they’re hybrid or electric) are not sustainable for urban transportation. I hope my community (the greater Seattle region) embraces this, and I think over the last decade or so this has begun to happen. Of course, the factors having the greatest impact on this are (a) the price of gasoline and (b) traffic levels.

    So, in the context of my opinions, I don’t have a lot of sympathy for complaints about transit being an inconvenience to auto traffic. When I’m riding the train or a bus, get those cars out of my way! And when I’m driving, trying to cross MLK, I’ll take a dose of my own medicine and be patient.

    1. C’mon my friend. What has been written in response to some of youre comments ought to be clear to you by now. Many of us LIKE Link and we appreciate that it is here and running fairly well for a brand new system. We are NOT wedded to the automobile nor to other internal combustion rubber tyred vehicles such as diesel/hybrid buses, though many of us accept that they will be with us for a generation or 2. Many of us believe that those who select or are required to use public transport ought to receive a fast prioritised trip, especially on rail, but on the bus too. If these concepts are difficult for you to comprehend, as they apparently are, perhaps you’ll find enjoyment on other blogs elsewhere – google Wendell Cox, just as an example.

      1. I comprehend this very well. I also disagree with it. If you don’t want anyone who disagrees with the primary view of most posters here to give their opinions, you can always just prevent me from posting.

        If all this site wants is people who agree with each other about transit, then it should be easy to limit people posting here to those that have the same opinion.

      2. Norman, NOT speaking as an STB blogger or moderator, I think I can safely say that nobody has a problem with the presence of someone “who disagrees with the primary view of most posters.” What bothers me and—based on many of the replies to your posts—many others are your ceaseless attempts to twist any interesting micro-level Link discussion (“how” does signal priority work, and how is it working?) to macro-level debate about (usually) settled political or policy issues (“Why” does Link have signal priority? What makes Link more special than cars and buses?). It’s tired and tiresome. Do you seriously just lack the restraint to hold off until Sunday?

        And your obsessive questioning of all things Link (ridership numbers, fare recovery rates, safety, traffic impacts, operating costs, headway frequency, on-time performance, etc.) compared to your utter lack of (expressed) interest in any of those same topics for traditional buses, BRT, commuter rail, or even automobiles makes it hard to believe that any of your comments are motivated by disinterested curiosity and not naked anti-rail ideology.

    2. Your post is off-topic. We’re talking about MLK signals. Next you’ll be asking “How about when you’re on a bus, and a bus gets in your way?” or “Why do cars have to stop for pedestrians in crosswalks, given that there are more cars?” Disagreements are fine… but we’re here to constructively criticize or compliment transit to make it better, not to continue the un-sustainable auto-centric culture of that last 65 years.

    3. Yeah dude. I was totally trying to find a seat on the bus and there was this huge train who got in my way and wouldn’t get up.

  21. How do the warning signals for the approaching train get triggered? The following has happened to me more than a few times:
    Waiting to cross MLK on my bicycle, I push the Ped Xing button. A train passes, and AFTER it has passed, the warning signals flash and the bell rings. After a very long wait, the Ped signal finally allows me to cross MLK legally.
    This most often occurs at S. Thistle St., which is a Ped X-ing only, not a cross street.

    You can also add S. Kenyon St. to the list of very long wait times to cross MLK. It’s really frustrating, especially when traffic is light. Why can’t you cross on demand when there’s no train within 1/2 mile? Surely the system knows where the trains are at any time, right?

    1. I believe this is related to my posting above. When a train requests signal priority SB at Othello Station and the signal has “timed out” it will delay the first signal that allows the train to leave the station – but the request is sent to the next several signals further south from Othello Station which give the train priority according to a set time from the request. These signals give the signal priority even though the train is delayed at the station. The priority is only for a set time period.

      The train is then stopped at the next signal when the Othello signal finally allows the train to leave – and then must re-request the priority from that point which probably looks like a phantom train to anyone waiting at Kenyon ST for example.

      If there was a way for train operators to know when the priority request would be delayed – we could wait to request it and avoid the incidents which you describe.

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