scope:

GENERAL DESCRIPTION.

These crossings are protected by colour light signals or motor worked semaphores that are capable of reverting to danger automatically behind a train. These signals shall be interlocked with the barriers so that it is not possible to clear the signals unless the road is fully closed by the barriers and a "Crossing Clear" is confirmed by the obstacle detector.

These crossings normally use four barriers, but on smaller roads where considerable widening would be needed to make four barriers practical, then provided there are no more than two tracks across the crossing, two barriers may be used.

The optimum distance between the crossing and the protecting signals is standard overlap distance, but is often varied as a result of taking into account other factors:-

• If signal spacing is better as a result, the protecting signals may be in the range 50m to 600m without further consideration.

• If the crossing is closed to road a significant time in any hour, then reducing to 50m minimises road closure time.

• Where two crossings are sited in the same signal section, then the distance to the second crossing is often unavoidably more than 600m. This can be minimised by moving the protecting signal at the first crossing to or towards 50m.

• Protecting signals may be within 50m if some appropriate SPAD mitigation is provided.

Where more than one MCB-OD is supervised from the same point, similar controls and operating arrangements shall be used for each crossing.

It shall not be possible to raise the barriers unless the signals are replaced to Red, and are free of approach locking, or the train has passed the signals and traversed the crossing.

The road approaches are protected by road traffic light signals and barriers on both sides of the railway. Audible warnings to pedestrians are provided.

The barriers shall normally be kept raised unless required to be lowered for the passage of trains.

The crossing is normally worked automatically and proved clear of obstructions during the closing phase by an obstacle detector system.

When lowered the barriers shall cover the whole width of the carriageway and footpaths. There shall be no space unfenced greater than 150mm width through which a pedestrian might gain entry to the crossing. On four barrier crossings, opposing boom tips shall be aligned within 50mm, and there shall be no gap between the tips greater than 65mm.

A scaled ground plan shall be produced showing the road and rail layout and all equipment sited at the level crossing.

Where there are four barriers, the entrance barriers shall be arranged to lower before the exit barriers. When the entrance barriers have fully lowered, then if an obstacle detector is reporting the crossing is clear, the exit barriers shall lower. (Details of obstacle detector operation and interaction with the barriers are given later.)

When all barriers have fully lowered, then if the obstacle detector system reports the crossing is clear, (and no other interlocking prevents it), the protecting signals shall be allowed to clear.

A minimum of two audible warning devices are provided. They shall be normally sited at the diagonally opposite nearside corners of the crossing facing onto the crossing area. Larger crossings may use more warning devices. See the audible warning section for more details.

Telephones for public use shall be provided.

All crossings shall be provided with a Datalogger that monitors and records the crossing operation.