Braking Questions - Comprehensive report on handbrake issues on freight wagons equipped with composite brake blocks

Wagons fitted with composite brake blocks can no longer be immobilised with the currently prevalent handbrake design on gradients of 40 ‰ due to the static friction coefficient of K and LL blocks, which is significantly lower than that of cast iron brake blocks. Current practice consisting in marking on the vehicle the maximum gradient on which it can be immobilised with a handbrake only represents an emergency solution and is wholly unsatisfactory from an operational point of view, as it does not allow a value to be deduced for a heterogeneous train consist. Moreover, the low proportion of vehicles in the fleet equipped with handbrakes could also signify insufficient holding forces with other friction pairings.

The present report provides a solution to the problem on a technical/physical basis, including the amendments to leaflets required as a result of the report, considerations regarding the impact on operations and transitional rules.

The holding force is introduced as a harmonised dimension for all rules on immobilising vehicles and trains in the future. It replaces the handbraked weight, which is still in use in some countries. It is also applicable when alternative means of immobilisation (e.g. drag shoes) are used in lieu of handbrakes. The holding force is used independently of the friction pairing and the location at which the vehicles are immobilised (station or open track). During a transition period, the handbraked weight can be converted into a holding force using conversion factors.

The report contains recommendations for future safety margins when immobilising vehicles and proposals for improving the effectiveness of handbrakes.