Trips by mass transit often contain frequent stops, which makes them slow, often slower than travelling by car. They also incur high costs to operators for the energy required to accelerate trains again after the stop and for the amount of rolling stock and staff needed. Furthermore the uneven loads of a train between different pairs of stops along its route increases costs, too, as the capacity of the train needs to be customized for the maximum load section. Eventually, the costs for building stations are increased by having to customize the length of its stopping bays to the maximum train length along the route, even if most passengers don’t board or alight there.
As all these costs are passed on to the passenger by ticket prices, trips by mass transit would not only be faster, but cheaper, too, if the number of intermediate stops could be reduced. On the other hand, as will be seen, different routing patterns often cause higher waiting times due to reduced departure frequency, or requires the passenger to change trains more often. Furthermore, different routing patterns may also require changes to the ROW, like passing lanes at stations or additional stopping bays.
In order to improve transit, one needs to look at different routing patterns. The most widespread concept is that every train stops at every stop along its route. This scheme has the above-mentioned disadvantages. Another concept is the skip-stop service pattern, by which trains skip certain alternating low-utilized stops along the route. The pattern is described here in more detail. It slightly reduces the line capacity on ROWs without passing lane by increasing the minimum headway.
Another service pattern is “zonal operation”, which is particularly suitable for operation between center and periphery. In this pattern all stations along the route are grouped into certain zones, depending on their distance from the center. Routes are then designed to serve a certain zone only, by traveling without stop between the center and the first stop within their zone, and then stopping at every station within their zone. Usually stations located at the border between different zones are assigned to both zones at once in order to allow interchange between different routes, thus allowing to travel between zones without having to connect at the center.
Further routing patterns are possible if trains are capable of splitting and joining during revenue operation. This enables trains to travel one section jointly, thus occupying only one timetable path, which is particularly useful where the capacity of the ROW is limited, and saving costs for staff, too, if trains are operated in human-driven mode, then to split at a certain station and from there onwards to serve different stops or even possibly different lines. If train units are capable of opening a passage way to coupled adjoining units, passengers could also change trains en route instead of at a station.
