Skip-stop

Skip-stop is a public transit service pattern which reduces travel times and increases capacity by not having all vehicles make all designated stops along a route. Skip-stops are used in both rail transit and bus transit operations. It is also used to describe elevators that stop at alternating floors and hence also used to describe building designs that exploit this design and avoid corridors on alternating floors.

When skip stops are used in rail transit, the transit operator designates stations as either major or minor, typically by ridership. Usually, all vehicles stop at the major stations, but only some vehicles stop at the minor ones.

Since one rail vehicle can only pass another by using an additional track, skip-stop may require additional investment in infrastructure if express services, where trains skip many stops along a route, are employed simultaneously with vehicles making stops on every station.

In systems that have no extra track for a faster train to pass a slower train, skip-stop may be employed either during busier travel hours to reduce travel time of a particular train, or during off-peak hours to raise efficiency by not stopping on "unpopular" stations.

In some systems, such as the New York City Subway, these are considered as two separate services (J/Z, the former 1/9; and formerly the D/Q—the latter of which were in fact two separate services), as if the two services were separate lines instead of two different stopping patterns on the same line. On other systems, such as Philadelphia's SEPTA Market-Frankford Line, they are distinguished by lights on the train, and stations skipped by half the trains are designated "A" and "B" stations depending on which trains stop there.

Chicago's elevated system used skip-stop service from the 1940s until the early 1990s, at which point all-stop service patterns replaced skip-stop service. This was done to reduce waiting times for passengers riding to or from "A" and "B" stations who could only take half of the trains. It also eliminated the need for a train transfer for passengers riding from an "A" station to a "B" station which required a transfer at an "AB" (all trains stop) station to complete their trip. Further, the system was simpler to use for new riders and visitors.

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