Schedule padding
In transportation, schedule padding, sometimes called padding,[1] is some amount of 'extra' time added to a schedule that allows it to be resilient to unpredictable delays. Schedule padding is, naturally enough, required only for transportation that operates on a fixed, published schedule, including public transport and airlines,[2]or if timed connections are important, like in many areas of passenger and freight transportation in which things that are being carried need to be transferred to another vehicle. It is not right, therefore, to think of something like a taxi as operating with schedule padding.
For simple trips, schedule padding may be relatively negligible. If a vehicle encounters little delay, it may simply arrive at its destination early and either transact its business or wait until the scheduled time for some rendezvous. In public transport, however, a number of timed stops may be strung together into a route, and some amount of schedule padding may be needed for each part of the trip. A transit vehicle must not pass a timed stop before it is scheduled to do so, and a conservatively-padded schedule, with much padding, can substantially reduce overall speeds and increase travel times beyond what might have been necessary. It is important, therefore, to think about the probability and distribution of certain types of delay events and the desired degree of on-time performance when padding in public transport timetables is established.
