Method and vehicle system for adjusting the speed of a vehicle before traffic signals

A method and vehicle system for adjusting the speed of a vehicle 1 leading up to traffic signals 2 comprising transmission by the signal 2 of signal-installation-specific information allowing determination of its position plus information of its switching state and time until a change thereof; receipt of this information by the vehicle 1 and determination of the distance to the signal 2 taking account of its own position; and on the basis of the determined distance, switching state, and time until a change thereof, a recommendation of a speed or speed range. Vehicle position may be determined by GPS via a vehicle navigation or information system. Signal position may be transmitted and/or signal identity may be transmitted to be combined with navigation data. A warning may be given if a stop is unavoidable of if a collision may be imminent and automatic braking action taken. The speed recommendation may link to a cruise control system. The system may consider actual or expected traffic queues.