A computerised method of creating data for a map from position data derived from the positions of a plurality of vehicles traversing a road network over a period of time in an area covered by the map, the map comprising a plurality of segments, each segment representing a portion of the road network, and each segment having a length and an associated speed profile indicative of average speeds of travel of vehicles along the portion of the road network represented by the segment at a plurality of time periods, the map further comprising intersections between segments representing intersections in the road network, each intersection having a plurality of manoeuvres associated therewith, the method comprising using a processing circuitry to: use a classification scheme to classify each manoeuvre at a plurality of intersections into a one of a plurality of categories, each category representing manoeuvres at intersections having similar characteristics; and determine a transit time for manoeuvres in each category by: analysing the position data to determine a real transit time for a plurality of vehicle trips on the road network; determining, for each of the vehicle trips, the plurality of segments and the plurality of manoeuvres forming the route through the map; defining an equation, for each of the vehicle trips, giving a predicted transit time for the vehicle trip, the equation being the sum of the travel time along the plurality of segments and the transit time for the plurality of manoeuvres, wherein the travel time for a segment is determined using the length of the segment and the average speed from the speed profile for the respective time period, and wherein the transit time for manoeuvres in each category form unknown parameters in the equation; and using the real transit time and the defined equation for each of the plurality of vehicle trips to determine the transit time for manoeuvres in each category. use a classification scheme to classify each manoeuvre at a plurality of intersections into a one of a plurality of categories, each category representing manoeuvres at intersections having similar characteristics; and determine a transit time for manoeuvres in each category by: analysing the position data to determine a real transit time for a plurality of vehicle trips on the road network; determining, for each of the vehicle trips, the plurality of segments and the plurality of manoeuvres forming the route through the map; defining an equation, for each of the vehicle trips, giving a predicted transit time for the vehicle trip, the equation being the sum of the travel time along the plurality of segments and the transit time for the plurality of manoeuvres, wherein the travel time for a segment is determined using the length of the segment and the average speed from the speed profile for the respective time period, and wherein the transit time for manoeuvres in each category form unknown parameters in the equation; and using the real transit time and the defined equation for each of the plurality of vehicle trips to determine the transit time for manoeuvres in each category. analysing the position data to determine a real transit time for a plurality of vehicle trips on the road network; determining, for each of the vehicle trips, the plurality of segments and the plurality of manoeuvres forming the route through the map; defining an equation, for each of the vehicle trips, giving a predicted transit time for the vehicle trip, the equation being the sum of the travel time along the plurality of segments and the transit time for the plurality of manoeuvres, wherein the travel time for a segment is determined using the length of the segment and the average speed from the speed profile for the respective time period, and wherein the transit time for manoeuvres in each category form unknown parameters in the equation; and using the real transit time and the defined equation for each of the plurality of vehicle trips to determine the transit time for manoeuvres in each category.