Skip-stop

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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.

[edit] Rail Operation

When skip stops are used in rail transit, the transit operator designates stations as either major or minor, typically by ridership. All vehicles stop at the major stations, but only half stop at the minor ones, which are given different designations such as "A" and "B".

Since one rail vehicle can only pass another by using an additional track, skip-stop reduces overall travel times without any additional investment in infrastructure. Express services, where trains skip many stops along a route, require either careful scheduling or places for faster services to pass slower ones. Rapid transit systems normally run too frequently for scheduling to offer a solution, and in some systems there is no place for the slower train to pull aside for the faster train to pass. Skip-stop reduces some of the increased travel time resulting from more passengers boarding and leaving vehicles. Rail skip-stop is normally employed during busier travel hours; trains make all stops during off-peak hours, such as evenings and weekends.

In some systems, such as the New York City Subway, these are considered as two separate services (J/Z and the former 1/9), 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, 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 CTA 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.

[edit] Helsinki commuter rail

Helsinki commuter rail uses extensively skip-stop services. Below there is a chart to demonstrate the skip-stop system in use.

 v • d • e Helsinki commuter rail network map

	Y							M
Karjaa	●							●	Vantaankoski					T	H	R		Z
Inkoo	●							●	Martinlaakso					●	●	●	Riihimäki	●	Lahti
Siuntio	●	S	U	L				●	Louhela					●	●	●	Hyvinkää	｜
Kirkkonummi	●	●	●	●				●	Myyrmäki					●	●	●	Jokela	｜
Tolsa	｜	｜	●	●				●	Malminkartano					●	●	｜	Nuppulinna	｜
Jorvas	｜	｜	●	●				●	Kannelmäki				G	●	●	｜	Purola	●	Mäntsälä
Masala	●	●	●	●				●	Pohjois-Haaga				●	●	●	｜	Saunakallio	｜
Luoma	｜	｜	●	●				｜					●	●	●	●	Järvenpää	●	Haarajoki
Mankki	｜	｜	●	●	E			｜			K	N	●	●	●	｜	Kyrölä	｜
Kauklahti	｜	●	●	●	●			｜			●	●	｜	●	●	●	––––––––––	●	Kerava
Espoo	｜	●	●	●	●			｜			●	●	｜	●	｜	｜		｜	Savio
Tuomarila	｜	●	●	●	●			｜			●	●	｜	●	｜	｜		｜	Korso
Koivuhovi	｜	●	●	●	●			｜			●	●	｜	●	｜	｜		｜	Rekola
Kauniainen	｜	●	●	●	●			｜			●	●	｜	●	｜	｜		｜	Koivukylä
Kera	｜	●	●	●	●			｜		I	●	●	｜	●	｜	｜		｜	Hiekkaharju
Kilo	｜	●	●	●	●	A		｜		●	●	●	｜	●	●	●	––––––––––	●	Tikkurila
Leppävaara	●	●	●	●	●	●		｜		●	●	●	｜	●	｜	｜		｜	Puistola
Mäkkylä	｜	｜	｜	●	｜	●		｜		●	｜	●	｜	●	｜	｜		｜	Tapanila
Pitäjänmäki	｜	｜	｜	●	｜	●		｜		●	●	●	｜	●	｜	｜		｜	Malmi
Valimo	｜	｜	｜	●	｜	●		｜		●	｜	●	｜	●	｜	｜		｜	Pukinmäki
Huopalahti	｜	●	●	●	●	●	––	●		●	●	●	｜	●	｜	｜		｜	Oulunkylä
Ilmala	｜	｜	｜	●	｜	●	––	●		●	｜	●	｜	●	｜	｜		｜	Käpylä
Pasila	●	●	●	●	●	●	––	●	––––––	●	●	●	●	●	●	●	––––––––––	●	Pasila
Helsinki	●	●	●	●	●	●	––	●	––––––	●	●	●	●	●	●	●	––––––––––	●	Helsinki
	Y	S	U	L	E	A	x	M	xx	I	K	N	G	T	H	R		Z

[edit] Bus Operation

In bus operations, skip-stop refers to a stopping pattern where buses do not stop at every block or at every designated bus stop, typically in a central business district. Skip-stop operation reduces travel time and increases the number of buses that the streets and bus stops are able to accommodate. With skip-stop operations, bus routes are typically grouped together by geographic area in order to provide a common stop for areas that are served by multiple routes. The skip-stop groups are sometimes identified by color or letter so that passengers and bus operators can easily identify their desired stop. A disadvantage with skip-stops is that passengers may have to walk farther or change buses to catch their intended bus, which increases travel time. Passengers may also be unsure about which bus stop to walk towards to catch their intended bus.

Skip-stops work best when buses are able to easily pass each other at bus stops, such as on a low-traffic street, street with bus stop pockets or dedicated busway with at least two lanes in each direction. If there is a large amount of other traffic on the street or only a single bus lane is provided, then buses have difficulty passing each other and much of the benefit of using skip-stops is not realized.

In Seattle, WA, which has an extensive local and regional bus system operated by three different transit agencies, skip-stops are used on 2nd, 3rd, and 4th Avenues in the downtown area. Bus routes on 3rd Avenue are grouped into Blue and Yellow stops, while bus routes on 2nd and 4th Avenue are grouped into Red and White stops.

In Portland, OR, Trimet and C-Tran buses use skip stops on the Bus Mall in Downtown Portland. The Bus Mall is under construction through May 2009. During construction, these buses are temporarily re-routed to 3rd and 4th Avenues, and grouped into skip-stops identified by letters A, B, C for southbound on 3rd Avenue and X, Y, Z for northbound on 4th Avenue.