A regenerative braking system for a vehicle includes a means 13 for storing details of one or more deceleration profiles for the vehicle; means for comparing 13, arranged to compare a current braking manoeuvre with the or a selected stored deceleration profile which generates an output signal, during the manoeuvre, representative of any deviation of the deceleration profile of the current braking manoeuvre from the ideal deceleration profile with which it is compared. This output can be used to drive a display 14 to provide feedback to a driver as to the efficiency of a braking manoeuvre. Multiple ideal deceleration profiles may be stored and the system arranged to compare a current braking manoeuvre with the most relevant stored profile. Profiles may be stored in association with spatial, temporal and/or environmental information.