In transportation schedule adherence or on-time performance refers to the level of success of the service (such as a bus

Bus

A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...

 or train

Train

A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...

) remaining on the published schedule.

There are many factors that can have an impact on on-time performance. Depending on the situation, the service may face regular delays or a service that usually performs on time may be occasionally behind schedule. Some of these factors include:

• Traffic
  Traffic
  Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel...
  
  :
  • Bus transport: The volume of automobile traffic on the bus's route can impact the bus's ability to keep on the schedule. While a route that is free of obstruction can remain on schedule or even move ahead of schedule, heavy traffic
    Traffic congestion
    Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...
    
     can slow down the bus behind its schedule. This can be due to regular conditions at the time of day, or an occasional or one-time event, such as a sports game or festival
    Festival
    A festival or gala is an event, usually and ordinarily staged by a local community, which centers on and celebrates some unique aspect of that community and the Festival....
    
     that draws a large crowd.
  • Rail transport: The volume of traffic on the route can cause even more delays for rail vehicles, because of tight scheduling at sidings and other meet points. On passenger railroads, freight traffic is especially problematic because of the length and slow acceleration of the freight train
    Freight train
    A freight train or goods train is a group of freight cars or goods wagons hauled by one or more locomotives on a railway, ultimately transporting cargo between two points as part of the logistics chain...
    
    s.
• Accident
  Car accident
  A traffic collision, also known as a traffic accident, motor vehicle collision, motor vehicle accident, car accident, automobile accident, Road Traffic Collision or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction,...
  
  : A collision that obstructs traffic flow can also tie up vehicles on the route until the accident is cleared and therefore cause them to be behind schedule.
• Detour
  Detour (road)
  A detour or diversion route is a route around a planned area of prohibited or reduced access, such as a construction site.Standard operating procedure for many road departments is to route any detour over roads within the same jurisdiction as the road with the obstructed area.On multi-lane highways...
  
  : A road closure that forces the bus to temporarily deviate from its regular route may cause it take more time than planned to reach its destination.
• Weather
  Weather
  Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
  
  : Inclement weather may cause a bus that usually remains on schedule to be behind as a result of precautions that must be taken by the vehicle's operator and other vehicles on the road. Trains might have to operate slower as a result of slippery rail
  Slippery rail
  Slippery rail is a condition of railways caused by fallen moist leaves that lie on and cling to the top surface of the rails of railway tracks. The condition results in significant loss of friction between train wheels and rails, and in extreme cases can render the track temporarily unusable...
  
   during the autumn season, and high wind can affect signal systems
  Railway signal
  A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train/engine drivers. The driver interprets the signal's indication and acts accordingly...
  
  .
• Increased ridership: When a special event takes place, the service may experience higher ridership levels than usual, leading to more time the bus or train may have to spend allowing passengers to board and depart.
• Breakdown
  Breakdown (vehicle)
  A vehicle breakdown is the operational failure of a motor vehicle in such a way that the underlying problem prevents the vehicle from being operated at all, or impedes the vehicle's operation so much, that it is very difficult or nearly impossible, or dangerous to operate, or else at risk of...
  
  : A disabled bus or train, besides being unable to complete its own route, may slow down others that follow on the schedule. As riders scramble to board a subsequent bus or train on the schedule, the higher ridership levels on that run may slow it down. Additionally, on a rail line, a disabled train may block other trains from passing, or may require track-sharing with opposing trains, thereby slowing service in both directions.
• Unrealistic scheduling: Many public transportation agencies are tax-subsidized, and therefore are often cash-strapped while attempting to maximize service provided to customers. In such cases, schedules that are written do not provide enough time for operators to travel along the route in the time allotted, and layover
  Layover
  In transportation, a layover, also known as lays over or stopover, is some form of a break between parts of a single trip.-In mass transit:...
  
  s are too short to allow enough recovery time, thereby seriously delaying the service on a regular basis.
• Clumping: On some bus lines with more frequent service, while one bus falls behind schedule while it is busy picking up and dropping off a large volume of passengers, one or more subsequent buses on the published schedule that pass these already cleared stops may have a nearly empty run, and may actually jump ahead of its scheduled time to the point that two or more buses are within close sight of one another, or in some cases, one bus is able to pass another. This phenomenon is sometimes known as clumping or bunching . When this occurs, the even spacing of buses on the schedule may be severely disrupted, leading to extremely long waits for those attempting to catch a bus with a more frequent schedule, and multiple buses arriving at once.

Improving schedule adherence

Transit agencies often take the following measures in attempts to improve schedule adherence on their routes:

• Modify schedules by adding running time, known as schedule padding. This is the most common solution, but agencies often add running time by cutting layover time, which adversely affects the ability to recover from unplanned incidents. If layover time is to remain the same, it may require an increased expenditure in the system's budget or a slight reduction in the number of trips.
• Cutting other under-performing services. The savings generated from eliminating or reducing other services may be used to improve service on other, higher-performing routes.
• Modifying routes to a route where buses can be less obstructed, when this does not interfere with the ability of riders to reach their buses.
• Splitting a long route into two or more shorter ones, as shorter routes are more likely to remain on schedule.
• Some cities have introduced bus rapid transit
  Bus rapid transit
  Bus rapid transit is a term applied to a variety of public transportation systems using buses to provide faster, more efficient service than an ordinary bus line. Often this is achieved by making improvements to existing infrastructure, vehicles and scheduling...
  
   services or limited stop lines on long, overcrowded routes. This involves the use of part of the route's budget to operate another line on the same route that stops only at key points. While the overall frequency of the original route is reduced, riders traveling over a longer distance have the option of obtaining a quicker trip on the limited-stop line.
• Some agencies and transport companies have installed GPS devices on their buses and trains to monitor the locations of the vehicles. By linking this real-time information with stop locations and predicted travel-times, the estimated time of arrival of the next service is then displayed at some stops.
• Customer interfaces: Some agencies and companies have made the GPS tracking data described above available to public transport users online, by a toll free number, or through the mobile web
  Mobile Web
  The Mobile Web refers to the use of Internet-connected applications, or browser-based access to the Internet from a mobile device, such as a smartphone or tablet computer, connected to a wireless network....
  
  .
• Accept the principle that A late journey always gets later. It is better for the majority that one journey is significantly delayed or canceled rather than delay many after because of knock-on effects such as clumping. This is more important for transportation such as railoads where vehicles are carefully scheduled to use limited infrastructure such as tracks.

Real-world examples

The following chart shows some examples of real-world on-time performance. The figures are always (unless stated otherwise) per vehicle, not per customer. This means that if 95 % of vehicles have less than 5 minutes of delay, one cannot conclude that 95 % of passengers experience less than 5 minutes of delay. Delays are usually greater during rush hour, therefore the delays per passenger are usually higher than per vehicle.

Operator	Mode of transport	Period	< 1'	< 2'	< 3'	< 5'	< 10'	< 15'	< 20'	< 30'	Comments	Source
SBB	All passenger rail	2010		84.3 %	90.7 %	95.6 %
DB	Intercity rail	September - October 2007	46 %		62 %	72 %	84 %		92 %	96 %	Figures disputed by DB AG, no official figures available
	Local rail		56 %		76 %	86 %	94 %		98 %	99 %
Amtrak Amtrak The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...	California Zephyr California Zephyr The California Zephyr is a long passenger train route operated by Amtrak in the midwestern and western United States.It runs from Chicago, Illinois, in the east to Emeryville, California, in the west, passing through the states of Illinois, Iowa, Nebraska, Colorado, Utah, Nevada, and California...	2010								47.7 %	> 550 miles, therefore on time is < 30' delay
	Capitol Corridor Capitol Corridor The Capitol Corridor is a 168-mile passenger train route operated by Amtrak in California. Because it is fully supported by the state, the Capitol Corridor operates under Amtrak California. It runs from the San Francisco Bay Area to Sacramento, roughly parallel to Interstate 80...						93.5 %				< 250 miles, therefore on time is < 10' delay
JR Central Central Japan Railway Company The is the main railway company operating in the Chūbu region of central Japan. It is officially abbreviated in English as JR Central and in Japanese as . Its headquarters are located in the JR Central Towers in Nakamura-ku, Nagoya, Aichi Prefecture.The company's operational hub is Nagoya Station...	All passenger rail	2010									Average delay 30 seconds (no distribution given)
Lufthansa Lufthansa Deutsche Lufthansa AG is the flag carrier of Germany and the largest airline in Europe in terms of overall passengers carried. The name of the company is derived from Luft , and Hansa .The airline is the world's fourth-largest airline in terms of overall passengers carried, operating...	Short/medium distance flights	November 2008 - March 2009						84.7 %			Arrivals
	Long distance flights							78.2 %