# Calculation of the interval between subway trains.

The braking time for a vehicle traveling at V = 30m / s (108km / h) is:

T = Vmax / G_frein = 22s
with G-Brake = 1.35 m / s²
The braking distance is D = 1/2 x v² / G-brake = 133 m.

This time or this distance is not essential for the calculation of the interval.

When the subways / trams are running and an accident happens, all trains must be able to stop urgently at the station, because travelers do not want the metro / tram to stop between 2 stations, otherwise the travelers panic and some travelers want to get off right away.

This is why the time interval between subways / trams is so long, 60-90s, while the braking time is 25s. This interval corresponds to the distance between 2 stations.

On the other hand, if 2 trainsets can stop in the same station one behind the other, this interval between trains is 2 times smaller, because 2 trainsets can enter a station one behind the other. The interval is then 30 to 45 s.

In addition, the average speed of these trains is 40% higher, resulting in an even smaller time interval.

## Contact : patrick.colsenet@gmail.com

Enseignant Lycée Touchard-Washington Le Mans

## Cause an accident on the line ....

Successive subways / trams will then stop at the next station