Nice concept: each bus stop in London has a unique number on it. Text it or enter it onto a web page and get ostensibly realtime information on when buses will be swooping in to pick you up. Unlike
the system NYC is trialling, there is no realtime map information. Which would be useful. But ETAs all by themselves would be useful. Except they're not because they are way too inaccurate. So they can't be relied on to judge when you should leave your house or leave work or duck out of a shop and into the rain. The system kind of works as a comedic diversion. We've been trying it every day this week. One day I checked every minute or two between 07:11 and when the bus actually arrived. According to the estimated time remaining, we should have expected a bus at 07:21, then 07:20, then 07:25. It eventually arrived at 07:27. I was mystified as to what happened between the 7:20 and 7:25 estimated times of arrival, as within a span of 2 minutes the bus got 5 minutes farther away. Was it going backwards?
Today was arguably funnier. If you're not familiar with London transit you might not realize how ludicrous this is, but you'll have to trust me -- seven #26 buses arriving within a 25-minute window is about as likely as the Queen giving me a lift to work in her Rover.
Not to worry, a few minutes later, a couple of those buses had vanished. And no, not by virtue of having arrived and then departed from the stop in question. Sigh. I hope I never find out how much it all cost.
7 comments:
It would be interesting to see if they are using GPS (+/- 100s of feet), or iPhone-like cell tower triangulation (+/- about 15 feet), or the ubiquitous London Camera system (+/- human reaction, terribly inaccurate) or fixed road side sensors reading RFID tags (expensive infrastructure, but fairly robust IF the network can handle the data and the signal to noise ratio is low).
Position inaccuracy, and the messy irregularities of humans, traffic, and weather can combine to the variable ETAs you're getting, probably.
I wonder if they're using the same system as LA. "Nextbus" is next to useless.
Not sure exactly what system they're using, can't find much detail on the implementation yet.
Joe, showing buses that don't exist is worse problem than ETA inaccuracy. You should watch Rick's piece on the NY bus schemes if you haven't had a chance yet -- the combination of dead reckoning + gps locator in a relatively cheap device seems to work well. And, really, just show me the bus location on a map in a realtime and I'll make my own ETA guesstimate.
london impl sounds similar to chicago's. texting the stop # produces margins of error > bus frequency. so: useless.
however, if you go online to see calculated arrival times, it's actually quite accurate. (though there are both ghost buses, and untracked buses).
i wish i knew 1) if they're using two different systems, or 2) why the same system would produce two different outcomes.
That is very strange. We haven't tried texting to see if the results would be different, I just assumed they'd be the same.
I don't know what system TfL's using, but generally these use three elements: GPS, triangulation, and dead reckoning (useful when signals from satellites and towers are weak; generated from speedometer/odometer data and a gyroscope).
It's possible that what's really happening here is a bug in the software that's receiving the bus data. I suspect that's more likely than problems with the onboard systems.
Probably, yes. Bugs in data collection and also estimation. I think it is GPS-based. Although I'm not sure it uses any dead reckoning. Nor would I guess is it nearly as cheap as the system you covered being trialled in Brooklyn. Supporting the bug theory: my stop on the 26 in the morning is only 4 stops in from the initiation point. So all those improbable buses queued up between 15-25 minutes away would not even have left the lot. So faulty scheduling or confusion over data received (multiple buses fired up in the lot at the same time?) I also note the 425, at the same stop, seems generally much more accurate. It's a different company running that line, which shouldn't matter. More importantly, it's much more in the middle of the overall 425 route, rather than near an end point.
Really I just want to see a map that shows the location of each bus and I can judge ETA for myself.
Post a Comment