Commercial maps often offer traffic awareness which is critical for many location based services. On the other hand free and open map services (such as government maps or OSM) are traffic oblivious and hence are of limited value for such services. In this paper we show that coarse information available from a commercial map routing API, can be dissected into fine-grained per-road-segment traffic information which can be reused in any application requiring traffic-Awareness. Our system MapReuse queries a commercial map for a (relatively small) number of routes, and uses the returned routes and expected travel times, to infer travel time on each individual edge of the road network. Such fine-grained travel time information can be used not only to infer travel time on any given route but also to compute complex spatial queries (such as traffic-Aware isochrone map) for free. We test our system on four representative metropolitan areas: Bogota, Doha, NYC and Rome, and report very encouraging results. Namely, we observe the median and mean percentage errors of MapReuse, measured against the travel times reported by the commercial map, to be in the range of 4% to 8%, implying that MapReuse is capable to accurately reconstruct the traffic conditions in all four studied cities.