A method of generating flow data indicative of speeds of travel within a navigable network in an area covered by an electronic map, the electronic map comprising a plurality of segments representing navigable elements of the navigable network, the method comprising a server performing the steps of: obtaining data indicative of the average speed of travel for the current time with respect to distance along a link of the navigable network, wherein the link is predefined by reference to the electronic map and comprises at least a portion of one or more navigable segments of the electronic map, and wherein obtaining the data comprises: obtaining positional data relating to movement of a plurality of devices in the navigable network, matching positional data relating to the movement of the plurality of devices in the navigable network to the at least a portion of one or more navigable segments of the electronic map that define the link, and filtering the positional data to obtain positional data relating to the movement of a plurality of devices along the link; sectioning the link to provide a plurality of sections (12, 14) along the length thereof, wherein the link is sectioned based on the data indicative of the current average speed of travel with respect to distance along the link by: analysing the data indicative of the current average speed of travel with respect to distance along the link, and sectioning the link when a current average speed differential along the length of the link is detected that exceeds a threshold; and generating data indicative of the average speed of travel for the current time in respect of each one of the plurality of sections (12, 14) of the link; and storing data indicative of the location of the link for transmittal together with data indicative of each determined section of the link, the data indicative of each determined section of the link being associated with data indicative of the average speed of travel for the current time for the section. obtaining data indicative of the average speed of travel for the current time with respect to distance along a link of the navigable network, wherein the link is predefined by reference to the electronic map and comprises at least a portion of one or more navigable segments of the electronic map, and wherein obtaining the data comprises: obtaining positional data relating to movement of a plurality of devices in the navigable network, matching positional data relating to the movement of the plurality of devices in the navigable network to the at least a portion of one or more navigable segments of the electronic map that define the link, and filtering the positional data to obtain positional data relating to the movement of a plurality of devices along the link; obtaining positional data relating to movement of a plurality of devices in the navigable network, matching positional data relating to the movement of the plurality of devices in the navigable network to the at least a portion of one or more navigable segments of the electronic map that define the link, and filtering the positional data to obtain positional data relating to the movement of a plurality of devices along the link; sectioning the link to provide a plurality of sections (12, 14) along the length thereof, wherein the link is sectioned based on the data indicative of the current average speed of travel with respect to distance along the link by: analysing the data indicative of the current average speed of travel with respect to distance along the link, and sectioning the link when a current average speed differential along the length of the link is detected that exceeds a threshold; and analysing the data indicative of the current average speed of travel with respect to distance along the link, and sectioning the link when a current average speed differential along the length of the link is detected that exceeds a threshold; and generating data indicative of the average speed of travel for the current time in respect of each one of the plurality of sections (12, 14) of the link; and storing data indicative of the location of the link for transmittal together with data indicative of each determined section of the link, the data indicative of each determined section of the link being associated with data indicative of the average speed of travel for the current time for the section.