Punctuality Board

Key point

on-time performance

On time means nothing until someone states how late is too late, so GMT holds no default tolerance. A rate travels with its tolerance: the same six arrivals are 2 of 6 on time under one and 4 of 6 under another.

An arrival exactly on the late limit is late, and one exactly on the early limit is early: the limits themselves are outside the on-time band. Drag the band and watch each row change between early, on time and late.

Turn on the second tolerance to see both rates at once.

1. The arrivals and the tolerance

Six trains due at a London station on Friday 14 June 2024, against a 15-minute late tolerance. The 09:00 arrived at 09:15 exactly, on the late edge, which is late. With no early tolerance the two early arrivals are on time.

Late toleranceEarly tolerance optionalSecond late tolerance optional

ISO 8601 durations of exact time: PT15M, PT1H30M, P1D. A day is 24 hours.

Compare

Early toleranceA second late tolerance

2. Late, early or on time

Tolerance

3. What the calls return

 

Worth trying: a 10-minute early tolerance turns the 12-minute early arrival from on time to early. Then the fall-back night, where the station clock shows no delay and the train was an hour late. Then 60 and 120 minutes side by side.

Reference: scheduleDeviation, classifyPunctuality and punctualityRate are the three calls behind every reading here. See the guide’s tolerance section and its rate section.