Fast trips can identify problems with the input data or conversion process. This function returns trip_ids for trips that exceed `maxspeed`.
gtfs_fast_trips(gtfs, maxspeed = 83, routes = TRUE)
The function looks a straight line distance between each stop and detects the fastest segment of the journey. A common cause of errors is that a stop is in the wrong location so a bus can appear to teleport across the country in seconds.