Some of the strongest wind -induced lateral perturbations of the vehicle -driver system on bridges are observed when passing the towers. Occupants may feel uncomfortable or unsafe as a result. The aims of this work are to characterise the wind velocity profile observed in the wakes of bridge towers and understand the mechanisms through which the vehicle -driver system responds. A test vehicle was repeatedly driven across 5 cable -supported bridges with towers, of which 4 have been studied. Observed changes in wind speed were between 7 and 20 m/s with reference wind speeds of 14 to 25 m/s. The spatial periods of the wind profiles varied between 1.0 and 3.5 vehicle lengths giving disturbances at frequencies of 0.7 to 3.2 Hz at 60 to 80 km/h. The results show that the driver overcompensates for the changes in aerodynamic loading at the towers and the handling response of the vehicle is dominated by steering input - rather than aerodynamic input - once the driver initiates steering compensation. It is also shown, in agreement with an existing conceptual model, that the amplitude of the driver's steering response is linearly related to the change in the vehicle's yaw rate immediately preceding the compensation attempt.