An event data recorder or EDR is a device installed in some automobiles to record information related to vehicle crashes or accidents. In modern diesel trucks, EDRs are triggered by electronically sensed problems in the engine (often called faults), or a sudden change in wheel speed. One or more of these conditions may occur because of an accident. Information from these devices can be collected after a crash and analyzed to help determine what the vehicles were doing before, during and after the crash or event. The term generally refers to a simple, tamper-proof, read-write memory device.