Almost all formal transportation systems have timetables, which describe when vehicles are to arrive at scheduled stops.
The ability of different transport modes to meet on time performance statistics depends on the degree to which they are affected by external factors.
For example, rail services often operate on a separated right of way, and so are not affected by road congestion.
When the comparison is made between the timetable, and the actual arrival or departure time, a rule is applied to determine how much of a deviation is permitted.
Numerous websites exist for reporting on punctuality for airlines, often operated by government departments.
[1] Iraqi Airways, an airline, uses a rule that aircraft that depart within 15 minutes of scheduled departure are on time.
[2] The 15 minutes rules for on time performance is commonly applied throughout the airline industry.
[4] OAG and Cirium regularly publish airline on time performance rankings and data.
But another method that saves resources is to calculate on time performance for only the start and end of the bus route, which can produce meaningful statistics.
One problem with this method is where very large stops or interchanges are not at the start and end of the bus journey, but in the middle, and the start and end of the route are bus depots or other small stops for which on time performance statistics are not as important.
This results in 76 percent of schools in Ontario and Quebec to have late departures by chance not choice.
Where on time performance is poor, passengers or goods may miss a connection, and so be forced to wait.
In some cases, the transit time allowed from one transport mode to another may be very small, and so any lateness can result in services being missed.
Transport systems that exist to deliver passengers and services to interchanges should be particularly concerned with achieving a good on time performance.
The economic cost of a large transport vehicle being delayed is much greater than a service that is almost empty.
Transit agencies often take the following measures in attempts to improve schedule adherence on their routes: The following chart shows some examples of real-world on-time performance.