 Common ways include varying the tone of the background color, or by running a weak line along the zone boundaries.Many transit authorities publish multiple maps of their systems; this can be done by isolating one mode of transport, for instance only rapid transit or only bus, onto a single map, or instead the authorities publish maps covering only a limited area, but with greater detail.Another modification is to produce geographically accurate maps of the system, to allow users to better understand the routes.