Since the early 1990s, vehicle manufacturers have been developing internal computer networks for cars and trucks. Computers now control (or are able to control): the engine ignition, vehicular emissions, throttle operation, automatic transmission operation, the prevention of brakes locking, the prevention of drive wheels spinning, the minimisation of sideways sliding, the timing and deployment of airbags, and many other functions. Sometimes included on this linked network of computers is the "Event Data Recorder" (EDR). Some makes of vehicles can record certain variables associated with the last 5 s of driving prior to an airbag being deployed. In 2004/2005, the American Institute of Electrical and Electronic Engineers (IEEE) developed a new Standard (IEEE 1616 - a voluntary standard) that suggests that EDRs by 2008 collect up to 8 s of data prior to a crash occurring. The Standard also suggests that the computer network from which the data is collected possess some degree of "crashworthiness" - a characteristic that is currently not required. There has been extensive research on the reliability of pre-crash data using this technology. For example, comparing on-board EDR data with crash sled test data, comparing them with data from staged collisions, and finally, with output from forensically investigated "real world" crashes. The consensus from that research is that the EDR data are "mostly" correct - but are not necessarily so. The research emphasises that if such data are to be used for law enforcement purposes, a full forensic investigation be undertaken first - collecting friction measurements, skid mark lengths, crush damage and so on. After calculations are produced using these "manual" processes, then the EDR data can be downloaded and interrogated. The primary purpose of such a methodology is to ensure that any results of the crash analysis obey fundamental laws of Newtonian physics. The consensus of the research is that downloading the data first then undertaking the (more subjective) forensic analysis would bias any subsequent investigation.
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