The accident data recorder (ADR; frequently abbreviated in German as UDS; also known as accident (data) writer) is a standalone electronic device that records pertinent data before, during, and after a traffic collision; it is similar to a flight recorder in this regard.
It can be installed voluntarily in motor vehicles (including automobiles, trucks, buses, motorbikes, trams, and special vehicles) in order to gather more precise data regarding the incidents that led to an accident. There are laws requiring some automobiles to have certain installations in several nations. The accident data recorder continuously captures different vehicle data (such as speed, direction of travel, longitudinal and transverse vehicle acceleration, status of the lights, turn signals, and braking, etc.), and it stores these data for a period of time before automatically clearing them.
Certain intervals of time (often in the two-digit seconds range) remain permanently saved before and after an event in the case of an accident (this is identified by a strong acceleration of the vehicle as a result of an impulse). This makes it considerably simpler to reconstruct events following an accident, allowing for the clarification of fault if necessary.
Since it frequently results in collisions while driving with blues and twos about compliance with legislation, many government vehicles (such as police or ambulances) are outfitted with it. The use of UDS in vehicles has the unintended consequence of making drivers more careful on the road. A study by the EU Transport Commission found that UDS users noticed a 20 to 30 percent decline in traffic accidents.
In crash tests, the accident data recorder is frequently utilized as a measurement tool by professionals or organizations.
Around 770 euros are spent on the installation (including subsequently), which may be deducted from premiums for some insurance plans. An expert can read the accident data recorder using an interface connection. Older models of the accident data recorder have a switch that allows the driver to promptly delete the stored information following an accident so as to avoid later guilt-related concerns. For use in corporate vehicles, for instance, this capability may be disabled.
Accident data recorders use micromechanical sensors to measure accelerations in two or three spatial dimensions, depending on the equipment. To be able to record the driving dynamic processes on the one hand and the collision dynamics themselves on the other, numerous sensor systems with varied resolutions are frequently used. Higher-class systems also have the option of sensing rotational movements in addition to the speed of the vehicle. The latter can be determined, for instance, using the wheel speed sensor input from the car. Higher-class devices may detect a GPS signal to determine position and speed as well as record any signals that are available on the car's internal CAN bus.
Approximately 20–30 seconds are recorded prior to and 10–15 seconds following an occurrence, depending on the manufacturer.
Currently (as of 2018) among the German-speaking nations, only two are known to be appropriate for accident data recorder retrofitting. Blacktrack Ltd. provides an affordable option that is mostly used by the insurance sector (e.g. AXA Winterthur in Switzerland). The UDS-AT, on the other hand, was created by the business partnership between Kast GmbH and Peter Systemtechnik GmbH and offers expanded recording and vehicle integration options.
Relying on current on-board signals (distance, speed, operating states of status inputs), residual path recording devices (RAG) from Mobatime AG are external devices that store data in a ring buffer for at least the previous 12 km. They lack their own measurement sensors, in contrast to an accident data recorder.