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The use of Heavy Vehicle Event Data Recorders (HVEDRs) in collision analysis has been recognized in past research. Numerous publications have been presented illustrating data accuracy both in normal operating conditions as well as under emergency braking conditions [1,2,3]. To date, the bulk of this research has focused on HVEDRs incorporated into the Electronic Control Modules (ECMs) employed by various manufacturers to monitor and control engine operation. Oftentimes, data associated with engine diagnostic faults include vehicle speed and driver input parameters that are later used in a collision analysis. In addition to the ECM, other electronic control systems may store data associated with fault conditions. For example, the Antilock Braking System (ABS) Electronic Control Unit (ECU), which is tasked with electronically controlling brake application air pressure to reduce wheel lockup, is such a unit that has the ability to store diagnostic information.

The Electronic Control Modules (ECMs) aboard many on-highway commercial motor vehicles contain event data useful to the investigation and reconstruction of motor vehicle collisions [1,2,3,4]. Methods of extracting such event data include: connecting to the ECMs through the vehicle's Off-Board Diagnostics Connector (a 6 or 9 pin connector typically found inside the vehicle near the driver's seat); connecting directly to any ECMs while they are still connected to the engine; and connecting directly to the ECMs after they are removed from the engine (a method typically referred to as a Bench image). This research is an attempt to document the effects of these data-extraction methods on the retention of the event data contained in the ECMs of the on-highway commercial motor vehicle engines manufactured by Detroit Diesel and Mercedes-Benz.

Event Data Recorder (EDR) technology has been incorporated into the Electronic Control Modules (ECMs) of many on-highway heavy trucks. One benefit of this technology is its applicability to vehicle collision investigation and reconstruction ( Goebelbecker & Ferrone, 2000 ; van Nooten & Hrycay, 2005 ). However, collisions that cause extensive damage to the truck may cause a loss of electrical power to the ECM, which might interrupt the data storage process. This research is an attempt to determine the effects of power loss on heavy vehicle ECMs 1 , and the associated effects on data collected by the EDR function. Controlled testing was conducted with Detroit Diesel, Mercedes, Mack, Cummins, and Caterpillar engines, and power failures were created by artificially interrupting power between the vehicle's battery and ECM at predetermined intervals. EDR data from the test vehicles were extracted after each test, and the presence or absence of new data was examined.