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Link light rail runs at grade on Martin Luther King Jr Way S with street traffic and pedestrians crossing the track at regular intervals. Coordinating signals to ensure that trains and cross traffic flow safely with minimal delays is an ongoing process that will continue after light rail opens for service.

Do you have questions about how traffic signals work together with Link light rail signals? If you do, please leave them in the comments. I will be meeting with an SDOT signal operations engineer this Thursday and will try to have your questions answered.

47 Replies to “Do You Have Link/Street Signaling Questions?”

  1. Here are a few of my questions.

    – 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.

    Hey Oran have you seen any more progress on MyBus tracking?

    1. What is the tracking technology? Is it built into to the rail system or is it GPS based?

      It’s SCADA. GPS wouldn’t work underground.

      1. “Windows based software” We’re doomed!

        Your traffic light has received an automatic update. Please wait while your traffic light reboots…

      2. The ticket machines also run Windows.

        Typically Windows software is just used as an interface to program the signal controller, which runs its own OS.

    2. Re: MyBus tracking

      I haven’t seen any more that I’m aware of. For those who don’t know, they can look at Link’s schedule in Metro’s Tracker system as Route 599 (overlapping the Tacoma-Lakewood Sounder shuttle route number). There is currently no real-time information, just scheduled times.

      1. I noticed the Route 599 thing too, and so I tried tripplanning a trip that would have to use the real 599 and it didn’t work…

      2. They also have Link (as ST 599) info in tripplanner, although it’s missing data for Beacon Hill Station.

  2. As a driver, if I miss a green turn signal, and there isn’t any oncoming traffic, but there is traffic going the same direction as me (eg I’m going east and want to make a left turn, and theres only east straight traffic, no straight west traffic), will the oncoming lanes get a red signal and the system give me a green? Currently, the system doesn’t seem to allow for any dynamic signal changes as conditions change.

    1. I don’t think so, as the change in cycle would put the timing out of whack for the next peak-direction train.

  3. Are there crosswalk buttons? If so, do they have priority over cars (I assume they don’t over rail)? Will half street crosses be allowed when a train is coming (green walk sign to cross car part of street, but red for train part)?

    1. From my observations: Crosswalk buttons exist on both sides of the street and in the refuge island between the tracks or platform edge for stations. It is possible to cross halfway. The train will sound its horn to alert you.

      I’ve seen countdown timers on ped signals at some crossings. It really helps with judging crossing time.

      I will ask about priority.

      1. How about the sections were half street crosses are forced at some stations? IE you must cross half of the street, press the crosswalk button again in the middle and wait another cycle to fully cross the street. This is pretty annoying if you’re trying to get across and not just to the station!

      2. Are you talking about at Othello Station? When I was down there you could cross the whole way in one cycle. It was close but you could do it walking at a normal pace. I know that they have made revisions to the signal timing since I was down there though.

      3. I have this problem at Cloverdale, where the pedestrian signal only changes to allow you halfway across. I just ignore it, because the light length is just as long, but that doesn’t seem safe.

      4. At Cloverdale, the actual walk signal (steady white walking person) doesn’t last very long (I haven’t timed it but it must be less than five seconds), but the countdown (flashing red hand with timer) lasts for 24 seconds. I would think that this is long enough for most people to cross the whole way. They will have needed to push the walk signal button of course to get a signal at all.

      5. Thel, were you given the walk signal only halfway? That is, the signal halfway gives you a walk signal but the one across the street remains a steady red hand. Or did the walking person appeared on all signal heads but turned into a flashing hand by the time you have crossed halfway?

        The flashing red hand doesn’t mean stop crossing, it means do not begin crossing if you have not already, you won’t have enough time. 29 seconds is a long time to give for crossing only half way, even for slow walkers.

        Engineers assume a walking speed of 4.0 ft/s when calculating the time given to pedestrians to clear the crosswalk. Edge curb-to-edge curb, it’s about 120 ft so it comes to 30 seconds which seems to be what was set.

    2. Along the SODO trail paralleling Link in SODO, the crosswalk buttons give a near immediate signal about half the time. I assume the rest of the time they’re some decision made that it was too recently a red light for cross traffic.

  4. Will I be able to drive right along with Link at 55, knowing I’ll have a constant stream of green lights?

    1. In theory, yes but the timing is not perfect. I’ve observed Link stopped at lights and missing its green wave a few times. And don’t forget that Link stops at stations and drivers don’t. Link on MLK follows the posted speed limit of 35 mph. I’ll ask them anyway.

      1. There were some changes made to signal software and timing several weeks ago after which Link trains started to get delayed or stopped at pedestrian only signals causing us to miss the signal cascade ahead of that crossing. This wastes a TSP ahead of these crossings and requires the train to request another after stopping again at the next signal.

        We never saw this problem before the timing/sofware changes were made.

        This is very puzzling since there is never a pedestrian cycle occuring – no indication of a walk request and traffic signal stays green. It is also unpredictable. Losing TSP at full intersections is predictable, infrequent and managable from the cab. It is the loss of TSP at these pedestrian only signals that makes no sense – and must be fixed to ensure smooth operation.

        Internally this issue has brought on a lot of finger pointing but no solution so far.

        Maybe SDOT can shed some light!

      2. Any chance they could post the control programming? Most control code is a variant of BASIC, and I bet our combined resources can solve the problem for free!

    2. You have to pull over and wait while it’s at a station. I’ve driven from Mt. Baker station to Boeing Access Road with a Link train.

      1. I’ve done this a couple of times too, and wished that I had someone else in the car with me to video the train as we rolled along side-by-side.

  5. With the addition of smoother lights for trains, east-west lights (particularly left turn lanes) have up to two cycles of wait times. Are they hoping to change that? East-west drivers are anxious!

  6. Somebody should invite Tim Eyman for a ride to see how real traffic synchronization works :)

  7. i am a moron who wants to make a u-turn against a red light, but there is a train in the way. what is SDOT doing to protect my right to t-bone light rail?

    1. They’re doing everything in their power to protect our rights as citizens. Don’t worry Jerry.

    2. You absolutely have that right! Once! Please drive a small vehicle at high speed.

      (not really. ;) )

  8. What is the highest practical frequency of trains using priority measures – more specifically, at what point are trains operating too frequently to allow priority without creating unacceptable backups on east-west crossings?

    1. I’ve heard that’s five minutes, which is probably fine for that corridor pretty much forever. North trains don’t have to go that far south – they can stop in SoDo. This is part of why I want my bypass in fifty years. :)

      1. I want the bypass in 30 years!…

        Actually sooner…20 years but that won’t happen… Next I want the run to West Seattle and points South with it looping back somewhere South of the Airport.

    2. What constitutes “unacceptable backups” would differ depending on whether you pose your question to SDOT or Sound Transit (in this case you’re asking SDOT, of course). SDOT is responsible for traffic signals and fielding complaints from drivers. ST (and Metro) are responsible for moving people to/from the airport. So there’s a bit of compromise in determining an acceptable car/train balance. The idea with the MLK signal software is that both autos and trains can generally run smoothly.

      This car/train compromise is interesting in light of the debate in Bellevue as to whether it’s possible to run their future light rail at grade through downtown. Here’s hoping to successful signal software!

  9. What’s the policy on the drivers using personal cellphones (voice/texting,etc) while the train in operation? How will it be enforced? (other than people youtubing drivers texting…)

    1. From the rulebook “R 1.12 USE OF ANY PERSONAL ELECTRONIC DEVICES – While operating any equiptment, the use of or appearance of such use of any electronic devices, accessories, and reading material is prohibited.” So, if you see any of us operators doing that, report us. It has been made clear to us by management.

  10. During early testing the two lights at Royal Brougham had a timing difference so that if you were moving slow (such as a bicycle coming out of the SODO trail headed west) you could easily get stuck between them. The first time this happened to me the police officer monitoring the intersection advised me to cross the tracks anyway.

    Has this timing issue been corrected?

    1. NB the trains have a speed limit of 10 mph because a security barrier must be lowered just north of Royal Brougham. If the operator goes any faster we get a forced safety stop until be get our proceed light. SB the barrier goes down further away from the train and speeds are higher – 25-30mph.

  11. I have a question about how the train stops if a car is broken down on the tracks. In other words, how automated is the Link train? Because here is a video of a Metrorail caught texting while operating a DC area Metrorail train. I hear they are fully automated. Is that true of Link, as well? If a Link operator is texting (Link operators will be completely hidden from passengers, as their door has a pull-down shade. Also, there will be no cameras in the operator compartment looking at the operator), and doesn’t see a car up ahead stalled on the tracks, will the train automatically stop?

    1. The Link LRV are all operator controlled, all the time. LRVs in Seattle (both Link and Slut) are just a modern streetcar or trolley. We are in control of the LRVs at all times.

      As to using a cell phone in the cab it would be hard to do while the train is moving. Your left hand is always on the master controler, the device that moves the train forward and applies the brake. If you remove it from the MC the deadman will stop the LRV. The right hand is used to ring the bell with the right thumb and to turn a switch on the dash to honk the horn. Both hands are in use at all times except at the stations, where a person just outside the cab could easily see the operator through the side windows and the windshield.

    2. So DC Metrorail is automated with operators controlling the doors with collisions and derailments yet Vancouver SkyTrain is automated and driverless and has had none of that in its history? Doesn’t mean that there were no fatalities or accidents though. There’s no way a driverless train can stop if someone decides to jump in front of it, unless some sensors are installed or emergency stop button is pushed (potential for false alarms and abuse) or is prevented by platform screen doors (people still can get trapped between the door sets).

  12. My question is how Link stopping and waiting at intersections along MLK impacts the schedule. Is it possible for the train to speed up in, say, the Beacon Hill Tunnel in order to stay on schedule, or would a train be delayed at that point?

    1. Right now the signals are not working on MLK as they should. Since May, both NB and SB bar signals are not cascading the entire route. Most of the time the trains are having to stop (and sometimes hard stops) because a light at a pedestrian crossing does not turn to “proceed” and the train has to stop and call the signal again over the call loop. Then once we get the proceed light, the train is already running behind the next light, and then will need to stop for that one, too. When you lose about three lights as we now average per trip, we start losing time from our schedules, and we usually get only 5 minutes to turn around at Pine Street.

      Speeding up in the Beacon Hill Tunnel trying to make up time is not possible. In the tunnel we have ATP (Automatic Train Protection) which sets a maximum speed the operator cannot exceed by more that 2 MPH, or the train shuts down. we will be going through it at between 35 and 40 MPH which is pleanty fast enough.

      1. It’s not fast enough if you’re behind schedule though. Too bad you don’t go 25 through Beacon Hill so you could go 40 if you get behind… none of the riders can tell how slow/fast a train is going in a tunnel anyway, can they?

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