Train connections

A major concern for SBB dispatchers and operators is connections between trains. If trains operate out of their normal order, passengers may be unable to make a scheduled connection. The dispatcher thus must often decide whether to have a train - or bus - wait for a train that is late.

The dispatcher has several bases for this kind of decision. In some cases, the dispatcher can follow rules set during creation of the national schedule. The usual form of such a rule is that if a train is more than a fixed number of minutes late, the connecting train - or bus - does not wait. For each train, the rulebook defines:

• how long - typically between 5 and 15 minutes - the train can wait for a late connection,

• under what circumstances a train must make unscheduled stops along its route for people who have missed their normal connection, and

• if a train is very late, when an extra train must be put into service to transport the people who are waiting for the late train. (An extra train may also be put into service to supplement a train that is very full.)

In many cases, however, the dispatcher must also apply his own judgement. In the Zurich dispatching center, a screen shows the dispatcher the trains arriving and departing at each station, in two parallel columns, with the train numbers on a vertical time axis.

The screen points out with a connecting line the connections that are in danger, given the lateness of the incoming train and the minimal time in which passengers are expected to be able to change trains. (This is 4 minutes in Winterthur, and 5 minutes in Zurich main station.)

On the screen, the dispatcher can give a command to "create" the connection and thus delay the departure of the outbound train accordingly. The decision on whether to do so depends on both the number of people expected to be making the connection and how long they would have to wait for the next train.

Altstetten: decision on whether to wait for connections

One task of a operator in the Altstetten control center is to monitor trains on the narrow-gauge Bremgarten-Dietikon railway.

If a train on that line is approaching Dietikon, but is running late, the operator can see exactly where the train is and judge whether to have the connecting suburban (S-Bahn) train at Dietikon wait or not. (Normally, the S-Bahn can wait for up to two minutes past its normal departure time.)