Schedule delay


Schedule delay is a term in transport modelling which refers to a difference between a desired time of arrival or departure and the actual time. Despite the use of "delay", it can refer to a difference in either the early or late direction.
The most common example is that of having a fixed work start time: if someone starts work at 0900 but actually arrives at 0850, they are incurring a schedule delay of 10 minutes. Alternative examples might include public transport - if a bus is scheduled to depart from a stop at 20-minute intervals and a person wishes to begin their journey between those intervals, they incur a schedule delay through having to retime their departure from the desired 0815 point to the bus departure time of 0820.
Schedule delay can be measured as a utility. The Small model of scheduling has the disutility of schedule delay decrease linearly towards zero as the actual arrival time approaches the desired time. The disutility of schedule delay for a late arrival or departure also increase linearly, but Small hypothesises that there can also be a fixed penalty component of schedule delay on the "late" side - e.g. arriving late for work is always bad, even if it is only slightly late.