A method of adaptively controlling a traction control system

A method of adaptively controlling a traction control system comprises the following steps, in step 50 it is determined if the traction control system has been activated, in step 54 reference speed and wheel speeds are determined, in step 56 it is ascertained if the wheel speeds are above a threshold, if yes step 58 determines if signals are noisy (e.g. if a high frequency content of the signals is significant or above a noise threshold), if the signals are not noisy then step 60 determines an instant ratio of driven to non-driven wheels, in step 62 a difference between the instant ratio and a dual rate filtered ratio is established, if the difference is greater than a threshold step 66 uses a fast adaptation, if the difference is less than a threshold step 68 uses a slow adaptation, step 70 applies a chosen constant for speed ratio adaptation to step 71 which applies an output adaptation speed ratio to step 72 that controls the system. The control method prevents false activation when, for example, a spare tyre or different final dive has been fitted. In another embodiment the system may be operated in response to short and long term wheel ratio.