The additional time buffer provided by systematically delaying trains at some
stops will have an especially strong effect on energy efficiency if the original
timetable is close to minimum running time. This may be seen in the following
diagram showing minimum energy demand against running time. Although the diagram
refers to a specific Swiss line, the characteristics of the plot is general.
Figure 1: Minimum energy demand against running time for a specific Swiss
line
Source: IZT based on Meyer et al. 2000
In the situation illustrated in the diagram a shortest time driving strategy
will lead to a running time of ~ 16,5 minutes. While between 16,75 and 17,75
minutes the energy difference will be of about 3 Wh/tkm, the one between 17,75
and 18,75 will be of 0,5 Wh/tkm only.
This illustrates that a general estimate of energy savings through
systematically delayed train is not possible and that the biggest effect will be
achieved for timetables that are originally very tight (small time buffers).
Even in these cases it has to be kept in mind that the energy savings can only
be realised for a small portion of the trips if no (additional) train delays
occur and rapid passenger boarding allows for short stops at
stations. |