An anomaly refers to an incident, usually a mechanical problem. By extension, we also use the term to refer to damage, which can be damage to a vehicle or even deterioration during transport.
Our trains are equipped with numerous safety devices in case of a technical failure. All it takes is for just one of these devices to be activated, and braking that brings the train to a halt will be triggered. Given RATP’s high level of preventative maintenance, such anomalies, while not impossible, are nonetheless extremely rare.
An anomaly can also concern fixed installations.
The most common incidents are linked to signalling. When a signal stays red for an unusually long time, it triggers the mandatory stopping of trains at that position. Safety procedures can be put into place to authorise the crossing of this signal point in complete safety, under certain conditions, while awaiting the arrival of the maintenance crew that will repair the anomaly.
Drivers and regulators are trained in these procedures, but they necessarily hamper operations, with traffic being slowed or even halted until authorisation is received to resume normal service once the repair work has been completed. There are numerous causes for this type of failure: an electrical problem, a fuse that has malfunctioned, a damaged switch, etc.