The two measures that get asked for, by operator and by four-weekly financial period — thirteen to a year, numbered from April, so Period 6 of 2026/27 is 16 August to 12 September 2026. The codes come from the same periods.csv the finance side uses. On-time performance is every recorded timing point along the route against the national window — 1 minute early to 5 minutes 59 late. Start time adherence is the same window applied only where a journey is timetabled to begin.
They are not the same question. OTP asks whether buses keep to the timetable along the route; STA asks whether they leave when they said they would. Early and late are reported separately because they are not the same failure: someone who arrives on time for a bus that has already gone has missed it, where a late bus is only late.
The terminus is excluded from on-time performance and reported on its own. A bus arriving early at the end of its journey is not a failure: the last leg carries padding, an interchange is where a bus is meant to wait, and nobody misses a bus that got there ahead of time. Counted in with the route it ran early on nearly three arrivals in ten against fewer than three in a hundred along it — a different measurement, not different driving — and it held First South Yorkshire 2.4 points below its route figure.
On-time observations against total, the shape the daily return takes.