the other. Higher-class systems also offer a possibility for measuring the rotational movements as well as the vehicle speed. The latter can e.g. be calculated from the signal of the vehicle's wheel speed sensor. The recording of any signals that are available on the vehicle's own CAN bus, is possible with higher-class devices as well as the detection of a GPS signal for position and speed determination. Depending on the manufacturer, about 20 to 30 s are recorded before and 10 to 15 s after an event. Are known today (as of 2018) in the German-speaking countries essentially two suitable for retrofitting accident data recorder. Blacktrack Ltd. offers a low-cost solution, which is mainly used by the insurance industry (e.g. AXA Winterthur in Switzerland). By contrast, the UDS-AT developed by the company consortium Peter Systemtechnik GmbH and Kast GmbH offers extended possibilities of recording and integration into a vehicle. Residual path recording devices (RAG) from Mobatime AG are external devices that rely on existing on-board signals (distance, speed, operating states of status inputs) and store them in a ring buffer for at least the last 12 km. In contrast to an accident data recorder, they do not have their own measuring sensors. Evaluation Reading out the data of an accident data recorder requires special software. The evaluation and interpretation of measurement data of a traffic accident require special knowledge in the areas of vehicle dynamics, accident reconstruction, metrology and last but not least the accident data storage technology itself. For UDS there is a separate order area for expert witnesses in Germany. The picture on the right shows the (unprocessed) data curves of a real accident recorded with a UDS. The measured accelerations, the speed and various status channels are plotted over time. It can be seen, for example, that vehicle special signals were switched on prior to the collision and the driver was previously still applying the brake. History The nowadays known accident data recorder was invented by Mannesmann Kienzle GmbH, which applied for a patent in 1992. The development began in Germany in the early 1980s with the two companies MBB and Kienzle, who pursued different concepts. In general, the black box was taken as a model, which was developed in the early 1950s in Australia by David Warren. Already in 1973, General Motors applied for a patent for a "vehicle crash recorder". Mannesmann Kienzle delivered the first