A timetable is a promise about time and distance. Divide one by the other and you get a speed, and some feeds promise speeds no vehicle has ever reached.
The patron saint of this crime is Lbo: a stop in Amtrak's feed, served by a Thruway Connecting Service bus between Merced and Gilroy, California. Its coordinates put it in northern Manitoba. The bus leaves Lbo and reaches Gilroy 2,479 km later, four hours on: 620 km/h, by road coach.
The law
A hop between two consecutive timed stops of a trip is too fast when it beats everything its mode can do:
| Mode | Limit |
|---|---|
| Bus, trolleybus, coach | 250 km/h |
| Tram, metro, monorail | 200 km/h |
| Rail | 450 km/h, above any scheduled high speed average |
| Ferry | 150 km/h |
| Cable car, gondola, funicular | 100 km/h |
| Anything else, air included | 1,235 km/h, the speed of sound |
Times in GTFS are usually rounded to the minute, so every hop is given at least a minute, and hops shorter than 2 km are never counted.
Only trips whose service still runs are judged. A hop to or from a stop at 0,0, or with its latitude and longitude swapped, is left to Null Island.
When a trip reaches a stop at an impossible speed and leaves it at a similar one (within a factor of two), the evidence marks that stop as likely misplaced: the trip seems to go out to it and come straight back. It is a guess, not a finding.
How to get pardoned
Put the stop where the stop is. Then check that the times either side of it are the times the vehicle actually takes.