Link at Othello – SounderBruce (Flickr)

In welcome news for riders, Sound Transit (ST) announced this morning that real-time arrival information for Link is now available on OneBusAway, Transit, Google, and other 3rd-party apps. As we reported last month, the update is limited to riders’ personal devices, as no new real-time signage will be available on station platforms for the foreseeable future. Originally planned for “early 2014“, the update finally responds in part to long-standing frustration at lack of rider information on what should be the region’s premier transit product. For SeaTac, Tukwila, Rainier Valley, Becaon Hill, and Downtown riders, this is the first type of real-time arrival they will have ever enjoyed.

So why has it taken so long? Beyond customary bureaucratic delay and budgetary prioritization, the central problem has been technological conflicts between ST’s internal-facing Supervisory Control and Data Acquisition (SCADA) system and the very different demands of user-facing applications and 3rd-party accessible data.

Problems with merely reporting SCADA data are evident to anyone looking at the real-time signs in Capitol Hill and UW Stations. SCADA tracks Link trains in between-station segments rather than continuously along the line, leading to a “step function” type of predictive ability. If you’re standing southbound at Capitol Hill, for instance, the next train may disappear from the screen right before it enters service, leading to signs saying “10, 16, 22” minutes etc even though the next train is only 4 minutes away. Once the train leaves UW, the “4 minute” train abruptly returns, dropping quickly to 2 minutes right before arrival. And the visual display may often conflict with the audio announcements of “2 minutes”, because the audio message gets put into the queue at a lower priority than other announcements such as elevator/escalator outages.

ST says the data will be most accurate in the middle of the line, in the Rainier Valley, where operations are most consistent. Beyond the terminal problems described above – which will endure southbound at Capitol Hill and now northbound at SeaTac Airport – other operational quirks will occasionally produce data gaps. If you’re standing northbound at International District station just before the start of PM peak, for instance, the train you’re waiting for may be coming from the Sodo base instead of from Angle Lake, but it will show as “scheduled” until it’s actually active on the line.

There will still be small discrepancies between OneBusAway, the visual screens, and the audio announcements – they have different rounding rules, for instance – but they should all be within a minute of each other. Real-time data will be especially useful for showing train delays and bunching, something that has been blind to riders since Link launched in 2009.

A universal real-time arrival design and implementation will have to wait a few more years, likely until Sound Transit owns and operates a Link-only Downtown Seattle Transit Tunnel beginning in or around 2019. But with wifi and/or cell service in all underground stations by the end of this year, underground riders will no longer face an information vacuum, and all riders with smartphones can know when their next train will arrive. This is a big, if belated, step in the right direction.

25 Replies to “Link Real-Time Arrival Now on OneBusAway”

  1. so the SCADA system is a simple block-occupancy detector system … makes sense as that’s what they need to run the line(s) … however it should be rather easy (tho not inexpensive) to shorten the lengths of the blocks which would provide more accurate time which could then be displayed at the stations (even if still slightly off … still better than nothing) …

    alternatively … couldn’t they add RFID tracking to the vehicles themselves so they can report their position and then computers could relay the accurate next train info to the station displays? trains run on fixed guideways so the ability to site RFID detectors should be simple, just a matter of how wide the spacing would need to be (they could literally be installed on every catenary pole along the line(s)).

    This would also enable the system to indicate how many cars are in each train as it simply has to count the number of pinged RFID tags that pass each sensor … which again could then be relayed to the station signage et al

    Personally I would be happy if ST would use some of the $$$ they’ve managed to save in construction for the addition of such a system.

      1. No. SCADA isn’t a signaling system; it receives data from the the signal system which is fixed-block.

    1. Actually, they could also add Doppler effect sensors in the tunnel too. These are used to detect how fast trains are moving for crossing gate activation, so they may even have some if those in their parts inventory someplace. Not sure if those have an output that could be used for this type of thing though.

    2. Why doesn’t ST operate a private position reporting system similar APRS or the AIS system used by ships. Trains and buses send beacons every 30 seconds with their location and speed (and anything else interesting they care to)? The technology is simple, cheap and proven. ST would effectively have real time reporting for any anything in their transit network.

      1. Those types of position reporting systems (AIS/APRS) probably work poorly (or at least inefficiently) underground for at least two reasons: (1) because the vessels’ transmitted radio signals are usually received at high, tower-mounted antennas, and (2) the reported position is usually generated by GPS.

      2. In that case the exceptions are the bus/link and Beacon Hill tunnels. Solution, ground based GPS signal and some receivers placed in the tunnels.

        You could even do it with out the ground based GPS in the tunnels, the system can simply send a beacon as it enters and leaves each station and maybe again at the half way point as a known location, from that you can estimate how far away the next train or bus is.

        Surely thats far simpler than the string and tape system of interfacing with the SCADA data?

      3. Suppose it _could_ work, but I can envision better, more reliable ways of handling the problem.

        I like the idea of many readers spaced along the tracks on poles and walls. Instead of a massive information gap caused by a single APRS receiver failing, you have numerous stationary readers for the passive markings (or perhaps RFIDs) on the trains. Since the readers always know where they are located, no GPS is required. A uniformly spaced pair of markers on each train would allow speed to be computed at each reader, and the system could also tell us how many train sets are in each consist. Even quite a few readers randomly being “down” would have very little impact on train data if they are installed densely enough.

  2. And if you have One Bus Away, please announce what it says to your fellow passengers. Then they won’t all have to look up the same thing on the monopolistically-priced data networks or remain in the dark if they don’t have a smartphone.

    1. I do better than that. I teach people how to access One Bus Away using SMS texting to 41411 and your stop number. The ID tunnel stop northbound is 621, southbound 624, the Pioneer Square northbound tunnel stop is 532, southbound 501.

      For example, if you are at the ID tunnel stop, and you want to see the 41s, you write this text Onebus 621, 41 and send to number 41411.

      No smartphone necessary. I’ve done it with a flip phone.

  3. Would appreciate it if someone who knows please tell me: I year 2017, why is it so hard for communications systems to communicate with each other? Or for everybody involved in any one endeavor to share the same one?

    This is literally a matter of life and death. How many people died needlessly at the World Trade Center over this matter? Every single emergency situation I’ve ever seen with the DSTT has always had massive communications problems. Though in fairness, far and away, not only the equipment’s fault.

    Is this a technical impossibility? Or how many people need their heads smacked together ’til their brains solidify enough to take care of this? Considering this last election, I wouldn’t be surprised if the United States of America is really the only country in the non-Third world that can’t get a handle on this.

    Where am I (pray to God) wrong?

    Mark Dublin

    1. New technology is often in the form of a new system or protocol. But instead of replacing older tech, they often just end up side by side. The larger the number incompatible systems, the more effort needed to get these systems to communicate with each other. Sometimes I think I should get out of computers and join a commune

    2. Computer philosophy: it’s a new system and better, so it should replace the old systems.

      Railroad philosophy: we’ll replace it when it breaks, so in 1981 we’ll still be sending out messages to freight trains on the branch lines in the Willamette Valley with the telegraph key that has been there for the past 100 years (and only put it out of service because construction near Union Station in Portland cut the wires to the power supply). It means everyone we put in that office will need to know the archaic communication protocol called Morse Code but that’s their problem.

      Notice anything incompatible with these two equipment philosophies?

      1. Well, in 1981, telegraph technology, Morse code, brass key and all, had been working more or less worldwide for 151 years.

        Variations developed using a cable running the width of the floor of the Atlantic Ocean, laid by a giant paddle-wheeled steamship called “The Great Eastern.” And when technology went wireless, Marconi still used code and a key.

        So my compatibility question is: Which philosophy chances the for worst incompatibility between networks of its own type?

        When the World Trade Center got hit, did first responders of different agencies have any better communications with each other than if the enough changes had been made so that a Marconi set still worked? And the whole world still used it?

        Because what gets to me are the intractable years’ long conflicts between individual modern systems. And seeming impossibility of choosing equipment that works for the particular job it was bought to do.
        Gut level, I wonder if the Morse telegraph engaged more trained human brains that knew without a video readout exactly what was going on along the whole section, and what needed to be done about it.

        But above all, I really think that the marketing of the 1880’s, however pompous and grandiose, never left the impression in the customer’s mind that one of those brass keys could let a wrong decision, by telegrapher or his bosses, the throw a switch in the right direction.

        Also wonder whether Old Number 97 really went off the bridge because the page froze up, and Steve Brody couldn’t hit the “Wait” button before he got “Killed.” Or just need some more machine oil for me “Logitech”. Or did a raccoon just fry himself in the wiring trying to get warm right at the crest of White Oak Mountain?

        “Lost his Airbrake” probably “scanned” better than “Page Became Unresponsive!” Do I make my point, Glenn?


      2. So sorry. Nobody will be able to drive to work on Tuesdays. That’s the day we do the software patches on all the self driving car systems.

  4. I guess now we know why they can’t tell when the train will arrive. The know nothing about its velocity and next to nothing about its location

  5. I know when my Sounder train is about 2 miles or roughly 2 minutes away, I can see it lights as it rounds the corner on approach from Tacoma to Puyallup :-) I then enjoy watching people take chances over 3 level crossings with lowering barrier arms. The fun ones are stopped on the crossing waiting for a traffic light to go green. The amusement never ceases

  6. I’m trying it out now. The experience is a bit interesting. If you click an actual station, you get blue and red numbers for actual arrival times. But, if you click “show route on map”, the trains are all gray with “position calculated by schedule”. What’s going on with the discrepancy here. It’s almost as if one piece of OneBusAway has the real-time arrival info and the other piece doesn’t.

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