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 locat

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.