1. A method comprising: receiving probe data from radar sensors of a plurality of vehicles at a road segment, the probe data comprising an identification of static objects in proximity to the respective vehicles at the road segment and geographic locations of the static objects; determining, using a processor, a first road boundary and a second road boundary at the road segment from the identified static objects received from the plurality of vehicles, the second road boundary being an opposite road boundary from the first road boundary; computing a width of the road segment from the identified first road boundary and the second road boundary by: determining, for each vehicle of the plurality of vehicles, a first distance between the first road boundary and the respective vehicle and a second distance between the second road boundary and the respective vehicle, combining, for each vehicle of the plurality of vehicles, the first distance and second distance to provide a determined width for each respective vehicle; and adding together the determined widths for each respective vehicle of the plurality of vehicles and dividing by a total number of vehicles; estimating a number of lanes at the road segment by dividing the computed width of the road segment by a predetermined average lane width; and updating a map database with the estimated number of lanes at the road segment.