An axle counter is a device on a railway that detects the passing of a train in lieu of the more common track circuit. A counting head is installed at each and of the section, and as each axle passes a head at the start of the section, a counter increments. As the train passes a similar counting head at the finish of the section, that counter decrements. If the net count is zero, the section is presumed to be clear for a second train.

Advantages

Axle counters are used in places such as wet tunnels, like the Severn Tunnel, where ordinary track circuits are unreliable. Axle counters are also useful where there are uninsulated steel sleepers which prevent the operation of track circuits. Axle counters are also useful on long sections where several intermediate track circuits may be saved.

Disadvantages

Axle counters may forget how many axles are in a section, due to say a power failure. A manual override is therefore necessary to reset the system. This manual override introduces the human element which may be unreliable too. An accident occurred in the Severn Tunnel due to improper resetting of the axle counters.

Rail technologies