Vehicle spacing control

A method of determining a safe distance (d safe ) between a first vehicle (1) and a second vehicle (2) moving ahead of the first vehicle, each vehicle having a state which comprises at least one of a position (s 1 , s 2 ), a speed and an acceleration of the respective vehicle, the method comprising the steps of: - collecting sensor data relating to the state of the vehicles (1, 2), - determining, using the sensor data and a time-dependent description of the state of the second vehicle (2), a state of the second vehicle (2) as a result of a maximum deceleration of said second vehicle, - determining, using a time-dependent model of the behaviour of the first vehicle (1) and said state of the second vehicle (2), a state of the first vehicle (1) as a result of said maximum deceleration of said second vehicle (2), and - determining, using said state of the second vehicle (2) and said state of the first vehicle (1), the safe distance (d safe ). Error margins of said sensor data are used to determine the safe distance, thus increasing the safety margin of the method.