1. A computer implemented method of generating and using an electronic horizon for use with an advanced driver assistance system (ADAS) of a vehicle, comprising: accessing, by a processor, a probability matrix stored in a memory having, in respect of each of one or more decision points of a road network, data indicative of a historic relative probability that each of a plurality of possible outgoing paths at the decision point will be taken by a vehicle for each of one or more possible incoming paths, wherein the data indicative of the historic relative probability that a given possible outgoing path will be taken is based upon positional data relating to the movements of a plurality of devices associated with vehicles with respect to time on the road network; using, by the processor, the probability matrix to determine data indicative of a relative probability that each of a plurality of possible outgoing paths associated with a decision point will be taken by the vehicle when confronted with the decision point; generating, by the processor, the electronic horizon from the determined data, wherein the electronic horizon defines at least a most probable outgoing path to be taken by the vehicle from the decision point; and providing, by the processor, data to the ADAS of the vehicle determined using the electronic horizon to provide assistance to a driver of the vehicle.