This paper proposes a combined approach of shock wave analysis and rule-based model to determine the time and location of freeway crashes using loop detector data. The model enables theoretical consistency with the underlying effects of freeway crashes on traffic flow patterns which are revealed through the real-time traffic data. The rule-based model captures the progression of the crash shock waves from the crash site by determining the arrival times of the backward forming and forward recovery shock waves at nearby loop detector stations. The experiment results highlight the appropriateness of the combined approach to estimate the crash location and time under various crash scenarios.