Some embodiments provide a method for a mapping service. For a set of road segments that intersect at a junction in a map region, the method generates an initial set of geometries for use in generating downloadable map information for the map region. For each corner formed by the geometries at the junction, the method determines whether to perform a smoothing operation. When a particular corner meets a set of criteria, the method modifies the geometries of at least one road segment to smooth the corner.