4 ms·

Neat. I had a similar idea a few years ago to make NextBus times more accurate... but fell down a rabbit hole trying to implement it as a cross-platform HTML ap

by eli 10y ago

Neat. I had a similar idea a few years ago to make NextBus times more accurate... but fell down a rabbit hole trying to implement it as a cross-platform HTML app and never actually launched. If anyone wants my idea: My perception of NextBus's arrival times are that they're based on a very naive algorithm. I think it might literally be assuming that all buses always move at an average 15 mph. Lots of ways to make that more accurate with collecting just a teensy bit of actual arrival time data.

stuckagain 10y ago
I don't know about other systems but I've spent time in the field analyzing NextMuni's predictions and they have no predictive power whatsoever. The first arrival time is weakly correlated with actual arrival, and the 2nd and 3rd times are not even correlated. It's useless, essentially.
- danaliv 10y ago
  I learned early on to discard the units when using NextMuni. The J will arrive in three. Three what? Nobody knows, but there will be three of them.
skuhn 10y ago
Back when NextMuni was only 99% worthless, Transit had a method of actually getting reasonable arrival times out of it. Since each bus has a published GPS location (in addition to the NextMuni time), you can use that with driving direction data to loosely get travel time. When the app did this you would initially see Next Muni times -- 2 minutes away! -- which would update a few seconds later for lines you were particularly looking at -- oh wait 20 minutes away! Apparently NextMuni either just displays the schedule (which is literally never right) or does some kind of extremely basic estimation like you said. Many times I have seen a bus arrival time listed that was physically impossible -- a bus a mile away arriving in 1 minute, for instance. Transit's method still fell down in the case of buses which appear on the route but are just sitting at the beginning of the line. It treats that as a bus that's en route, but in my experience they just hang out for as long as they feel like it. I learned to look up the locations on the map and discard those, just annoyance #475 of public transportation.

by eli 10y ago

stuckagain 10y ago

I don't know about other systems but I've spent time in the field analyzing NextMuni's predictions and they have no predictive power whatsoever. The first arrival time is weakly correlated with actual arrival, and the 2nd and 3rd times are not even correlated. It's useless, essentially.

danaliv 10y ago
I learned early on to discard the units when using NextMuni. The J will arrive in three. Three what? Nobody knows, but there will be three of them.

skuhn 10y ago

Back when NextMuni was only 99% worthless, Transit had a method of actually getting reasonable arrival times out of it. Since each bus has a published GPS location (in addition to the NextMuni time), you can use that with driving direction data to loosely get travel time. When the app did this you would initially see Next Muni times -- 2 minutes away! -- which would update a few seconds later for lines you were particularly looking at -- oh wait 20 minutes away! Apparently NextMuni either just displays the schedule (which is literally never right) or does some kind of extremely basic estimation like you said. Many times I have seen a bus arrival time listed that was physically impossible -- a bus a mile away arriving in 1 minute, for instance. Transit's method still fell down in the case of buses which appear on the route but are just sitting at the beginning of the line. It treats that as a bus that's en route, but in my experience they just hang out for as long as they feel like it. I learned to look up the locations on the map and discard those, just annoyance #475 of public transportation.