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November 24, 2010 at 9:57 AM

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Snow routes hamper bus tracker site; developer hoping to make changes

Posted by Katherine Long

Tech-savvy Metro bus riders who have come to rely on, an application and website that lets you know when the next bus is due to arrive at your stop, were dismayed to find this week that the service didn’t work during the snowstorm.

The reason: Metro stopped feeding the datastream that OneBusAway uses to update passengers about the progress of their bus. The information was out-of-kilter, and therefore not useful, when the buses went off their regular routes and on snow routes, Metro said. The approximately 40,000 unique visitors that use OneBusAway every week just saw the published route times, not real-time information.

We probably won’t see a fix to the system over this winter, said Brian Ferris, a University of Washington graduate student and developer of OneBusAway. In an interview via email, Ferris described how he is hoping to make some changes to OneBusAway so it can deliver reroute, cancellation and service alert information through its various interfaces.

“Updating OneBusAway is actually the easy part,” Ferris said. “The hard part involves converting the information published at King County Metro's alerts site into a form that OneBusAway can understand for automatic delivery so you just see the pieces that affect you when you are waiting at a stop. This won't tell you when your bus is coming, but at least you'll have a better idea of if it's coming at all or where it might be rerouted.”

Next year, all of Metro’s buses will be equipped with GPS systems, which is one important piece of the puzzle, Ferris said. But that won’t solve all the issues: “The next big challenge is being able to communicate specific details about detours, cancellations, and delays in real-time to the mobile device in a rider's hand when they are waiting outside at a stop,” Ferris wrote.

“King County Metro's service alert page, the emails, the Twitter account: these are all important tools for communicating to the rider, but they are a fire hose approach that tend to overwhelm riders with information and miss them where they need it most: at the stop.”

You might wonder how OneBusAway works without GPS. Ferris explains: "Vehicles are tracked using a combination of odometer readings from the bus and radio synchronization beacons installed throughout the county. Generally, the odometer reading tells us how far a bus traveled. If we know the path of the bus, we can track the progress of the bus along the route. In practice, the odometer reading becomes inaccurate over time, so the agency uses a series of some 300+ radios beacons installed throughout the county as synchronization points. Every time a bus passes a beacon, it re-zeros the odometer and future position updates are relative to that last known beacon. A bus might typically pass 5-10 beacons over the course of its route."

Ferris points out that Metro was one of the first agencies in the country to have real-time bus tracking, “and they did it before GPS was cheap and ubiquitous,” he said. “The downside is that while agencies who came later to the game have GPS-based systems, KCM (Metro) now has to upgrade and like any government agency, resources are thin and the pace isexcruciatingly slow. “

Ferris has a generals exam/thesis proposal due in three weeks that he should probably be working on, “but my thesis is on OneBusAway and the way it changes riders' use of public transit (positively, as you might imagine).

“So while I'm sure my advisors might prefer I spend more time writing research papers and less time hacking on OneBusAway, I find time to improve on the site when I can,” he said.

OneBusAway is open-source software, and Ferris said he welcomes help from the community in adding new features. In addition to the site itself, Ferris also writes a blog about OneBusAway at

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