Among driver assistance systems recently applied to PTWs (ABS, CBS, etc.), the autonomous braking without input from the rider, named Active Braking (AB), is one of the most promising safety functions. The potential benefits of the AB are encouraging, although the improper activation of the AB is dangerous for the rider. Therefore the triggering must occur only when the vehicle is in stability conditions and the obstacle is no longer avoidable neither by braking nor by swerving.

In the present paper the last-second swerving maneuver is analyzed to identify the minimum swerving distance (Lsw) the rider requires to avoid the collision against an obstacle by turning, as an input for the triggering logic of the AB system. A physical model to define the minimum swerving distance is proposed. To validate the model, an experimental campaign was carried out using a scooter equipped with a prototype AB system and involving 12 test riders. The tests showed the good prediction capability of the Lsw algorithm for different riding styles and different scenarios with fixed obstacles.