SACEM (railway system)

The name means "Driver Assistance, Operation, and Maintenance System".

[5] The SACEM system enables a train to receive signals from devices under the tracks.

[6] A receiver in the train cabin interprets the signal, and sends data to the console so the driver can see it.

If the system determines that the speed might be unsafe, and the driver does not change it within a few seconds, SACEM engages the emergency brake.

SACEM also allows for a reduction in potential train bunching and easier recovery from delays, therefore safely increasing operating frequencies as much as possible especially during rush hour.

SACEM cab signalling (far left) on the MI 09 , showing a speed limit of 100 km/h (62 mph)
A situation authorized by SACEM, an MI 84 trainset enters Auber station while an Altéo trainset has not completely cleared the platform.
Lineside signal on RER A taken over by SACEM, as indicated by a St. Andrew's Cross (⨯)
SACEM cab signalling on the MI 2N Altéo , showing a speed limit of 30 km/h (19 mph)