Where is My Ride?

Sorry for the long delay in reporting from the technology fronts. We have been extremely busy getting ready for the rail startup in just a few weeks (working on all of the technology at the stations and behind the scenes that you can’t see) and in pushing the Automatic Vehicle Location project forward to fruition (as I started to talk about here).

One of the exciting things we are working on is enhancing the trip planner and website to provide better information about where the vehicle you care about is and when it will arrive. The latter problem while not trivial is actually the easier of the two to report on. In fact we have recently enhanced our website to give predicted arrival times for the next 3 buses at any given stop (link). Please take a look at it and let us know what you think. Currently this information is based on scheduled arrival time, but as we turn on the Automatic Vehicle Location system we will start replacing scheduled time with estimated time (based on the present location of the vehicle and its latest speed).

The trickier bit is if we should, and how we should display the real-time location of our vehicles once the AVL system is installed. The advantage to displaying the latest location of all of our fixed route vehicles is that individual riders can figure out which vehicle will best meet their needs and it greatly improves the transparency of the system. The down side to displaying this information is that people will count on the data being precise and as everyone should be aware of by now, technology is not always as accurate as we would like (think airplane arrival times or medical billing :-)). What we don’t want to happen is to put information out there that a specific bus is 3 blocks away when it is really 1 block away. People will act on the information in front of them and may miss a bus they wanted. This is not what we want to accomplish with AVL.

I think the key is to display the information in a way that quickly indicates how precise and how reliable it really is. All AVL systems have to pick a frequency of vehicle location updates. For bandwidth and communication cost reasons it is impossible to query the bus and train vehicle every second to know where it is. Practically there is little value in querying a bus every second for its location when it is moving at 5 miles per hour. Conversely it is bad to query a train at 5 minute intervals when it is moving at 60 miles per hour (the stated location will be up to 5 miles away from the true location of the train). For this reason our system will attempt to balance the frequency with the velocity of the vehicles and find a happy medium. But as with all things used by many people, it will not be possible to please everyone with the compromise we reach.

Given this challenge of frequency and real-time accuracy we are left with the issue of how to display the information in a meaningful and non-misleading manner. I pose this challenge to the Austin community as I have yet to find any transit agencies with AVL systems that seem to have solved this conundrum perfectly. For your consideration, here are some of the agencies we have found with AVL that are attempting to visually display the most recent location of their bus fleets. You be the judge and let us know what you think works best.
King County Washington Note: Shows last time the vehicle was querried
Chicago Transit Authority Note: Nice display of Google base map and option to pick routes
Next Bus Note: This is a private company that integrates the approach for many agencies

There may be others, and we would love to hear about them, but we would really like to hear your thoughts on this matter.

15 thoughts on “Where is My Ride?

  1. Grant

    I have to say, I like the CTA interface w/ the Google map best. The Washington County Java applet is slick, but it’s not as easy to connect with and harder to get the information I would want quickly.

  2. scottw

    I also prefer the CTA/google website. The interface is familiar (to anyone who’s used Google Maps), fast, and polished — and JavaScript is a lower bar to entry than full-fledged Java.

  3. Ben

    The most awesome, web 2.0-ey thing I can think of is this (I’m a web developer, so I realize this isn’t a trivial thing to implement): Google map, with an icon of the last poll with the relative time of the last poll (“2m ago” or “less than a minute ago” etc.). This icon is bold and opaque, fading from green to red depending on how old the data is for further indication on reliability. THEN, project a ghostly icon ahead of this with an estimated actual position… make this about 50% transparency and only white. Tag it with the word “estimate” and as it gets further from the last polling, it should reduce even further in opacity until it just entirely fades. Do it all with JavaScript.

  4. Scott

    As a bus rider, I don’t really care where the bus is now, I care how long it is until the bus arrives at my stop. I’d like to see just the minutes to arrival interface with times made accurate with location data and the average speed of this bus at this time of day.

  5. Kirk Talbott

    Scott and Tom, I am glad you brought this up. I think when will the bus arrive (which we plan to deliver through as many means as possible) is the most important piece of information the AVL system can deliver, but that is the hardest piece of information to deliver correctly. When the vehicle will arrive assumes knowledge about where the vehicle is, how fast it is traveling, but most importantly what will happen between now and when the vehicle arrives. That last piece requiring a crystal ball.

    So by telling you where the vehicle was last spotted and how fast it is moving (which I can do pretty accurately) you can guess as well as I can when it will arrive. If you are wrong you can plan your wait according to your personality. If you count on the system to tell you when the bus will arrive you don’t know how accurate it will be and you can’t adjust your behavior based on your personal style of travel. Hence the question of whether to give the public all of the facts and let them derive their own conclusions, or tell the public when we think it will arrive and have the public ridicule us for being wrong at our guess. After all, the rider already knows the scheduled arrival time which is the goal for any given vehicle.

  6. Kirk Talbott

    By the way, thanks for all of the other feedback on styles and other features in a best of breed where is my bus.

  7. Tom

    No system is perfect. Instead of hesitating for fear of the errors (that will always exist) I encourage you to try to calculate the next arrival time and measure your errors. If the AVL is working you’ll eventually get the actual time and location from the bus that can be compared to your crystal-ball estimate.

    In addition to the location and speed of the bus I’m waiting for you have the time it took the last few buses to get from that location to my stop. Including this information makes it a more difficult problem but hopefully you can measure the impact it has on the error in your estimates.

  8. Don Dickson

    I’m happy just to see another blog post about buses. Y’all have been spending an inordinate amount of time playing with your new train set. 🙂

    I once had a train set. I can relate.

    I liked the interface.

  9. markchacon

    I agree that the most important use of GPS to a transit rider is for the projected arrival time at a stop. This is followed by automated stop announcements inside the bus, which requires an on-board computer to be able to calculate the vehicle’s current location along the route.

    While it is difficult to exactly determine arrival time, I do not understand why this is such a challenge for Capital Metro. Many other transit agencies in the United States already have this technology. Some use private systems such as NextBus (which I felt performed poorly during a trial by Denver’s RTD a few years ago). Other cities have developed their own algorithms, and I am sure that some of these peer transit agencies can give Capital Metro advice on which systems work best. In general, I don’t believe the public needs the system to be exact (up to the second); as simply the knowledge that a bus is 5 minutes late would be a huge improvement over the current situation.

  10. yawnmoth

    Something that could be done would be to have some sort of subscription service for when a bus is at a particular bus stop.

    ie. if the bus is two stops away from the one you normally catch the bus at, you get a text message or something alerting you to that fact. You then proceed to the bus stop and enjoy the ride.

  11. dwilson

    I created an iPhone web application that supports Capital Metro that does a great job of telling you when your next bus is. Once you enter in your route information, it shows the timetable on the front page whenever you visit the site. This makes it a one click operation to see when your next bus leaves. Check it out: Transitly.

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