A method for controlling traffic signals to give signal priority to a vehicle travelling along a planned route, which is divided into sections. The method comprises the steps of receiving a report from the vehicle which comprises at least the next few sections along the planned route, determining whether the reports contain at least one section on both sides of an intersection, and, if this is the case, controlling the traffic light at the intersection to give priority to the route through the intersection, for the vehicle to enjoy signal priority treatment. According to the invention, a signal priority method is provided which allows the planned route of the vehicle to be predicted well in advance. The possibility of advance planning is obtained by describing the planned route of the vehicle in terms of predefined sections of the route.