13 Scheduling (transportation)

In public transport, bus bunching, clumping, convoying, piggybacking or platooning refers to a group of two or more transit vehicles, running along the same route, which were scheduled to be evenly spaced, but instead run in the same place at the same time. This occurs when at least one of the vehicles is unable to keep to its schedule and therefore ends up in the same location as one or more other vehicles which are supposed to be behind it.

A clock-face schedule or cyclic schedule is a timetable system under which public transport services run at consistent intervals, as opposed to a timetable that is purely driven by demand and has irregular headways. The name derives from the fact that departures take place at the same time or times during the day. For example, services with a half-hourly frequency might leave at 5:15, 5:45, 6:15, 6:45, 7:15, 7:45 etc.

Dead mileage, dead running, light running or deadheading in public transport and empty leg in air charter is when a revenue-gaining vehicle operates without carrying or accepting passengers, such as when coming from a garage to begin its first trip of the day. In this case, the vehicle is said to be deadheading.

In transportation, dwell time or terminal dwell time refers to the time a vehicle such as a public transit bus or train spends at a scheduled stop without moving. Typically, this time is spent boarding or deboarding passengers, but it may also be spent waiting for traffic ahead to clear, trying to merge into parallel traffic, or idling time in order to get back on schedule. Dwell time is one common measure of efficiency in public transport, with shorter dwell times being universally desirable.

The General Transit Feed Specification (GTFS) defines a common format for public transportation schedules and associated geographic information.

In public transport in the United Kingdom and Australia, hail and ride is boarding or alighting a mode of public transport by signalling the driver or conductor that one wishes to board or alight, rather than the more conventional system of using a designated stop. Hail and ride is used primarily in bus transport. The act of requesting a hackney carriage to stop is also termed 'hailing'.

A journey planner, trip planner, or route planner is a specialized search engine used to find an optimal means of travelling between two or more given locations, sometimes using more than one transport mode. Searches may be optimized on different criteria, for example fastest, shortest, fewest changes, cheapest. They may be constrained, for example, to leave or arrive at a certain time, to avoid certain waypoints, etc. A single journey may use a sequence of several modes of transport, meaning the system may know about public transport services as well as transport networks for private transportation. Trip planning or journey planning is sometimes distinguished from route planning, where route planning is typically thought of as using private modes of transportation such as cycling, driving, or walking, normally using a single mode at a time. Trip or journey planning, in contrast, would make use of at least one public transport mode which operates according to published schedules; given that public transport services only depart at specific times, an algorithm must therefore not only find a path to a destination, but seek to optimize it so as to minimize the waiting time incurred for each leg. In European Standards such as Transmodel, trip planning is used specifically to describe the planning of a route for a passenger, to avoid confusion with the completely separate process of planning the operational journeys to be made by public transport vehicles on which such trips are made.

In scheduled transportation, a layover is a point where a vehicle stops, with passengers possibly changing vehicles. In public transit, this typically takes a few minutes at a trip terminal. For air travel, where layovers are longer, passengers will exit the vehicle and wait in the terminal, often to board another vehicle traveling elsewhere.

A public transport timetable is a document setting out information on public transport service times, to assist passengers with planning a trip. Typically, the timetable will list the times when a service is scheduled to arrive at and depart from specified locations. It may show all movements at a particular location or all movements on a particular route or for a particular stop. Traditionally this information was provided in printed form, for example as a leaflet or poster. It is now also often available in a variety of electronic formats.

In public transport, a request stop, flag stop, or whistle stop is a stop or station at which buses or trains respectively stop only on request; that is, only if there are passengers or freight to be picked up or dropped off. In this way, stops with low passenger counts can be incorporated into a route without introducing unnecessary delay. Vehicles may also save fuel by continuing through a station when there is no need to stop.

Route capacity is the maximum number of vehicles, people, or amount of freight than can travel a given route in a given amount of time, usually an hour. It may be limited by the worst bottleneck in the system, such as a stretch of road with fewer lanes. Air traffic route capacity is affected by weather. For a metro or a light rail system, route capacity is generally the capacity of each vehicle, times the number of vehicles per train, times the number of trains per hour (tph). In this way, route capacity is highly dependent on headway. Beyond this mathematical theory, capacity may be influenced by other factors such as slow zones, single-tracked areas, and infrastructure limitations, e.g. to useful train lengths.

Schedule padding—sometimes called simply padding, or recovery time—is some amount of 'additional' time added to part or all of a schedule, in excess of the expected duration, that allows it to be resilient to anticipated delays and increase the chance that the published schedule will be met. In some cases, excessive padding may be intentionally added to make it unlikely that the schedule won't be met, or to prefabricate an earlier-than-scheduled completion. Padding may have only a temporary positive impact, and many clients perceive this as a deceptive strategy.

The symmetry minute is a significant time point in the clock face timetables used by many public transport operators. At this point in the cycle, a train in a clock-face timetable meets its counterpart travelling in the opposite direction on the same line. If this crossing time is constant across a network, connecting times between lines are kept consistent in both directions.