Wheel slide protection

This may be initiated automatically when the Wheel Slide Protection system senses loss of adhesion, or the driver can operate it manually.

Wheel flats on railway vehicles are very evident by a distinct “bang-bang” noise made in time with the speed of the train.

[citation needed] The controlled slip has the effect of conditioning the contamination layer on the rail (scrubbing action) thereby improving the level of friction and enhancing the ability of the train to stop.

Failing to recognize and respond correctly to railhead contamination or environmental conditions which cause low adhesion can lead to safety incidents and accidents such as a signal passed at danger, collision or station overrun.

Using lineside markers each driver gets his train up to speed and then makes a Full Service brake under normal adhesion conditions.

On the second run the driver will experience the sound and sensation of the WSP activating and operating blowdown valves on the brake cylinders, and the stopping distance will be considerably greater.

Although this only provides an approximation of how a train will behave during low adhesion, it does ensure that the driver can recognize the onset of wheelslide and will know the correct actions to take when it occurs.

Examples of this kind of equipment are manufactured by Knorr Bremse (EP compact, EP2002) Faiveley Transport (EPAC) and POLI Wabtec (ATHENA).

Manufacturers of WSP equipment include Faiveley Transport, Knorr-Bremse, Wabtec, DAKO, KES & Co GmbH, Mitsubishi, Siemens, Selectron Systems AG, ABB and LCA Ballauri.

In the UK, British Rail Research adopted two approaches including a laboratory simulation method to all WSP approvals from around 1992, and track testing using carefully conditioned paper tape adhered to the railhead.

The paper tape method used in the UK is believed to offer a realistic representation of the challenging very low adhesion conditions encountered during the autumn leaf fall.