Some embodiments provide a method for a mapping service. The method generates an initial set of geometries for a road graph defined for a map region. The road graph includes several road segments and junctions aggregated into roads. The method identifies an overlap between a first geometry of a first road segment and a second geometry of a second road segment. The first road segment and the second road segment are parts of different roads and do not meet at a junction. The method automatically modifies at least one of the first and second geometries in order to prevent the first geometry and second geometry from overlapping. In some embodiments each geometry is defined by a set of vertices that specify its boundaries. The method of some embodiments automatically modifies the vertices of at least one of the first and second geometries.