field trials of load-sensing valves fitted to articulated vehicles are described. the valves were fitted to the rear tractor axle and modified the braking on that axle, more nearly balancing the braking distribution to the load distribution in both the laden and unladen vehicle condition. the trials concerned over 250 british road service vehicles fitted with valves, with a similar number without valves acting as controls. two classes of vehicle were used: "maximum capacity" (30-32 ton gross vehicle weight) and "medium capacity" (22-24 ton gross vehicle weight). during a period of three years, records of accidents involving all these vehicles were examined, and those which occurred on public roads, totalling 757, were analysed in detail. the evidence showed that load sensing valves reduced (but did not eliminate) jack-knifing accidents for both sizes of vehicles but the overall accident results were disappointing. the trials emphasised the need for the vehicle braking parameters to be carefully chosen and for an in-service means of checking that the valves were still functioning as intended. (a)

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