An electronic braking system (WBS) suitable for commercial vehicles which tow trailers, which has on the towing vehicle, braking control of all the axles and a device for setting the braking demand for the trailer which is so adjusted as to equalize the utilization of adhesion between said towing vehicle and trailer. The system includes two adaptive control loops (30a, 30b) which are adjusted sequentially in a co-ordinated manner in order to set respectively the towing vehicle and trailer braking to levels where overall train mean decelerations approximate closely to those corresponding levels demanded by the driver and at the same time set the distribution of braking to seek to achieve equal utilization of adhesion between the tractor and trailer. The system also uses deceleration errors to sequentially adjust the two adaptive control loops.