Integration of data sources on traffic accidents

General interest geographic information is routinely produced by several public agencies. In cities, the use of smartphones and other mobile devices generates an increasing amount of unofficial georeferenced data. Although official data have usually higher reliability, it takes longer to be updated and made available, while the opposite occurs with unofficial data. This work explores the potential for integrating data from both official and unofficial sources. We present a case study with two traffic accident datasets in the city of Belo Horizonte, Brazil. We compare official traffic accident data to unofficial data collected from the mobile app Waze. We found that 7% of accidents reported by official sources have also been reported by users of Waze. Accidents reported only by official sources are concentrated in the central region, while those recorded by Waze are mostly on some major roads all over the city.