To increase police officer awareness of incident locations, the Dutch police developed and implemented a location-based notification system (LBNS). This mobile service notifies police officers proactively to warrants, agreements and police focal points in their current vicinity. To assess the accuracy, efficiency, effectiveness and user experience of this service, a longitudinal field evaluation was conducted with thirty police officers over four months. The results show that using the LBNS, police officers were better informed of relevant information in their environment and this led to positive operational results. Users considered the interface clear and easy to use. However, users indicated that the system presented too many or non-relevant notifications and that the system is overly complex. Recommendations for further development of the LBNS are to mitigate unwanted interruption by intelligent filtering of notifications and integration of system components. © 2008 ACM.