A method of operating a vehicle comprising at least a first vehicle retarding subsystem controllable to retard the vehicle, and processing circuitry coupled to the at least first vehicle retarding subsystem, the method comprising the steps of: acquiring, by the processing circuitry from the first vehicle retarding subsystem, at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; and determining, by the processing circuitry, a measure indicative of a retardation energy capacity currently available for retardation of the vehicle, based on: the acquired at least one value indicative of current energy accumulation by the first vehicle retarding subsystem; a predefined model of retardation energy accumulation by the first vehicle retarding subsystem; and a predefined limit indicative of a maximum allowed energy accumulation by the first vehicle retarding subsystem.