Breaking the fourth wall of technology

[szasz]

The city buses fairly recently got scrolling signs and recorded announcements of upcoming stops, sourced from some kind of positioning data (which surprisingly does not appear to be GPS). It's all kind of neat to see the stops rolling by on the sign as the bus travels, but today the sign on my bus repeatedly interrupted itself with bright red

Comments

[jlindquist]

That smells like a loose power connection on an Alpha sign. I wonder what they're using for position data. Do the announcements come when you're within line-of-sight to the stop? Maybe a radio beacon in the stop's shelter?

(Or maybe I'm WAY overengineering this in my head? :-) )

[recursive]

Oh, hey, it's been a while since I played with on of those. (Vik K. had one.) But, it does seem familiar now that you mention it.

(I made a cruddy python script to spit text out on it.)

[szasz]

I didn't think about that they might have flaky power connections; I assumed they were crashing.

I thought they used GPS for position data, but they don't. They appear to just know the distance between stops and are programmed with the particular route they're on. Then they just read the odometer, or something. I suspect this because I was once on a #2 Red bus but the sign apparently thought it was the #5 Green route. The sign just nonsensically called out stops along the Green route as we drove along, completely independently of where we actually were. Clearly GPS would be far superior. Back in the old days they had LORAN, I believe, but that was in the early 80's and that wasn't too reliable either.

I find that really disappointing. I think it's the cause of most of the errors in the web site and SMS system they have where you can find out when your bus is due to arrive at your stop.

[struggler]

the buses if philly have those and I wanted to know how they work. once one of the scrolling signs told me it was january 14th 2027. this was some time over the summer.