In the mid-1970’s General Motors introduced airbag technologies in a limited number of its vehicles. With the airbag technologies came event data recorders (EDRs), whose role at that time was primarily for the purpose of assisting in the triggering of deployment events, for diagnostic purposes, and for future research and development. Around that same time, interest was growing within governmental agencies, including the National Highway Traffic and Safety Administration (NHTSA) and the Office of Technology Assessment (OTA) in the use of automotive recording equipment to gather and study crash data to be used for safety research and development. Both NHTSA and OTA conducted studies that resulted in an increased level of interest in crash data collected not only through controlled tests, but also through alternative collection programs. EDR technology was an obvious alternative, offering in some cases, superior data by capturing real life crash data from real life events. Since then, NHTSA has been using EDRs to support its crash investigation programs.

An EDR device is defined by the NHTSA as “a device or function in a vehicle that records the vehicle’s dynamic, time-series data during the time period just prior to a crash event (e.g., vehicle speed vs. time) or during a crash event (e.g. delta-V vs. time), intended for retrieval after the crash event… the event data do not include audio and video data.”

All motor vehicles with airbag safety devices contain some form of an EDR device, but currently only General Motors and Ford offer commercially available tools for the downloading and/or retrieval of EDR data. In addition, the data currently being recorded varies from manufacturer, model and year, and in some case, from point of impact. While additional manufacturers have announced their intention to voluntarily provide tools that will allow for the commercial retrieval of EDR data, an August 2006 ruling by the NHTSA (set forth in 49 CFR Part 563) will require such commercial retrieval by the year 2011 on all models with EDR devices (most are required by 2010). In addition, the August 2006 NHTSA ruling requires manufacturers to meet minimum requirements on the EDR devices of all vehicles manufactured by 2011 (2010 for most vehicles), including requirements that the EDR devices record a specified minimum standard set of data elements, within a minimum specified degree of accuracy, and with a minimum standard for survivability of the EDR device following a collision.

While the data elements themselves do not on the surface, answer all questions of how a collision occurred, some of the elements will be instructive on specific issues regarding vehicle operation (such as speed and seat belt use), but more importantly, the data elements when used in conjunction with other accident reconstruction techniques will allow for a substantially more accurate picture of what actually occurred in any given collision.

Currently, data elements being recorded on many General Motors and Ford models may include some or all of the following: vehicle speed, engine speed (in RPMs), percent throttle, braking status, longitudinal or forward post crash velocity changes, lateral accelerations, and seat belt usage. Again, what is recorded varies according to make, model, year and in some cases, point of impact. However, with the August 2006 NHTSA ruling, the specified minimum data elements will be required to be recorded on all models manufactured in 2011 and beyond. The following tables, taken from the August 2006 NHTSA ruling, set forth the data elements required for minimum recording:

TABLE I – DATA ELEMENTS REQUIRED FOR ALL VEHICLES EQUIPPED WITH AN EDR

Data Element	Recording Interval/Time (Relative to time zero)	Data Sample Rate Sample per Second
Delta-V, longitudinal	0 to 250 ms	100
Maximum delta-V, longitudinal	0-300 ms	n.a.
Time, maximum delta-V	0-300 ms	n.a.
Speed, vehicle indicated	-5.0 to 0 sec.	2
Engine throttle, % full (or accelerator pedal, % full)	-5.0 to 0 sec.	2
Service brake, on/off	-5.0 to 0 sec.	2
Ignition cycle, crash	-1.0 sec.	n.a.
Ignition cycle, download	At time of download	n.a.
Safety belt status, driver	-1.0 sec.	n.a.
Frontal air bag warning lamp, on/off	-1.0 sec.	n.a.
Frontal air bag deployment, time to deploy, in the case of a single stage air bag, or time to first stage deployment, in the case of a multi-stage air bag, driver	Event	n.a.
Frontal air bag deployment, time to deploy, in the case of a single stage air bag, or time to first stage deployment, in the case of a multi-stage air bag, right front passenger	Event	n.a.
Multi-event, number of events (1,2)	Event	n.a.
Time from event 1 to 2	As needed	n.a.
Complete file recorded (yes, no)	Following other data	n.a.

TABLE II – DATA ELEMENTS REQUIRED FOR ALL VEHICLES UNDER SPECIFIC CIRCUMSTANCES

Data Element Name	Condition for Requirement	Recording Interval/Time (Relative to time zero)	Data Sample Rate (Per Second)
Lateral acceleration	If recorded	0-250 ms	500
Longitudinal acceleration	If recorded	0-250 ms	500
Normal acceleration	If recorded	0-250 ms	500
Delta-V, lateral	If recorded	0-250 ms	100
Maximum delta-V, lateral	If recorded	0-300 ms	n.a.
Time maximum delta-V, lateral	If recorded	0-300 ms	n.a.
Time for maximum delta-V, resultant	If recorded	0-300 ms	n.a.
Engine RPM	If recorded	-5.0 to 0 sec.	2
Vehicle roll angle	If recorded	-1.0 up to 5.0 sec.	10
ABS activity (engaged, non-engaged)	If recorded	-5.0 to 0 sec.	2
Stability control (on, off, engaged)	If recorded	-5.0 to 0 sec.	2
Steering input	If recorded	-5.0 to 0 sec.	2
Safety belt status, right front passenger (buckled, not buckled)	If recorded	-1.0 sec.	n.a.
Frontal air bag suppression switch status, right front passenger (on, off, auto)	If recorded	-1.0 sec.	n.a.
Frontal air bag deployment, time to nth stage, driver	If equipped with a driver's frontal air bag with a multi-stage inflator	Event	n.a.
Frontal air bag deployment, time to nth stage, right front passenger	If equipped with a right front passenger's frontal air bag with a multi-stage inflator	Event	n.a.
Frontal air bag deployment, nth stage disposal, driver, Y/N (whether the nth stage deployment was for occupant restraint or propellant disposal purposes)	If recorded	Event	n.a.
Frontal air bag deployment, nth stage disposal, right front passenger, Y/N (whether the nth stage deployment was for occupant restraint or propellant disposal purposes)	If recorded	Event	n.a.
Side air bag deployment, time to deploy, driver	If recorded	Event	n.a.
Side air bag deployment, time to deploy, right front passenger	If recorded	Event	n.a.
Side curtain/tube air bag deployment, time to deploy, driver side	If recorded	Event	n.a.
Side curtain/tube air bag deployment, time to deploy, right side	If recorded	Event	n.a.
Pretensioner deployment, time to fire, driver	If recorded	Event	n.a.
Pretensioner deployment, time to fire, right front passenger	If recorded	Event	n.a.
Seat track position, switch, foremost, status, driver	If recorded	-1.0 sec.	n.a.
Seat track position, switch, foremost, status, right front passenger	If recorded	-1.0 sec.	n.a.
Occupant size classification, driver	If recorded	-1.0 sec.	n.a.
Occupant size classification, right front passenger	If recorded	-1.0 sec.	n.a.
Occupant position classification, driver	If recorded	-1.0 sec.	n.a.
Occupant position classification, driver	If recorded	-1.0 sec.	n.a.

For more information on the August 2006 NHTSA ruling, go to our link for EDR Legal Updates/Administrative.