The public performance measure (PPM) measures the performance of individual trains advertised as passenger services against their planned timetable as agreed between the operator and Network Rail at 22:00 the night before. PPM is therefore the percentage of trains 'on time' compared to the total number of trains planned.

A train is defined as on time if it arrives at the destination within five minutes (ie 4 minutes 59 seconds or less) of the planned arrival time for London and South East or regional services, or 10 minutes (ie 9 minutes 59 seconds or less) for long distance services.

Where a train fails to run its entire planned route calling at all timetabled stations it will count as a PPM failure.