Black box 101: Understanding event data recorders

All new cars have some form of EDR

Published: January 2014

Popularly known as "black boxes," event data recorders (EDRs) have helped investigators solve the mysteries of airplane crashes for decades. Now they’ve become standard in almost every new car sold.

Event data recorders track vehicle data such as speed, acceleration, braking, steering, and air-bag deployment before, during, and after a crash.

First introduced by General Motors in basic form on air-bag-equipped models in the mid-1970s, EDRs were being used by various manufacturers in 64 percent of all new models by the 2005 model year, according to the National Highway Traffic Safety Administration (NHTSA). The Insurance Institute for Highway Safety (IIHS) says more recent data shows all new cars have some form of EDR. But the specific information gathered varies by auto manufacturer, and some companies make it easier to retrieve data than others.

Despite their presence in cars since the mid-1990s, they haven't fulfilled their potential, because automakers collect different data and use dissimilar systems to retrieve it. Now that will change, following a rule by the National Highway Traffic Safety Administration (NHTSA) that took effect Sept. 1, 2012.

The rule standardizes the data collected by the black boxes and how it can be retrieved. An issue prompting this rule came to light during the Toyota unintended acceleration crisis when Congressional hearings revealed that the company had only one computer in the United States that could read data from these recorders.

A new NHTSA proposed rule would require these EDRs in all light-passenger vehicles, starting September 1, 2014.  NHTSA estimates that approximately 96 percent of model year 2013 passenger cars and light-duty vehicles were already equipped with EDR capability.

The significance of this measure is in the specifics of what data it requires such devices to collect and its guidelines for how the data should be accessed.

The data must include:

  • The forward and lateral crash force.
  • The crash event duration.
  • Indicated vehicle speed.
  • Accelerator position.
  • Engine rpm.
  • Brake application and antilock brake activation.
  • Steering wheel angle.
  • Stability control engagement.
  • Vehicle roll angle, in case of a rollover.
  • Number of times the vehicle has been started.
  • Driver and front-passenger safety belt engagement, and pretensioner or force limiter engagement.
  • Air bag deployment, speed, and faults for all air bags.
  • Front seat positions.
  • Occupant size.
  • Number of crashes (one or more impacts during the final crash event).

Privacy experts have expressed concern over the release of such data, which can be used in court cases to prove fault in an accident. States have different laws governing the release of the data.

According to NHTSA, captured data is the property of the vehicle owner. But even on vehicles where it is accessible, special tools are required to get it. The IIHS says police or investigators can access the data with the owner's consent, or can obtain a court order to gain access if the owner refuses.

NHTSA says field studies have shown that the devices can increase driver safety by helping modify driver behavior, and the agency cites studies showing commercial fleets have seen crash reductions of as much as 30 percent in vehicles so equipped.

A study by the agency determined: "The results of the engineering analysis show that EDR data can objectively report real-world crash data and therefore be a powerful investigative and research tool, by providing very useful information to crash reconstruction experts and vehicle safety researchers. Due to significant limitations however, EDR data should always be used in conjunction with other data sources."

NHTSA estimates manufacturer cost to comply with the regulations will be about 17 cents per car. (Read Consumers Union calls for changes to strengthen U.S. car-safety net.)

Consumers Union, the advocacy arm of Consumer Reports, has supported standardizing black-box data, so accident investigators can use it to improve the safety of future vehicles and crashes. We've spoken to trauma centers that say that the data, in individual cases, would be invaluable in diagnosing injuries of the accident victims.

But we also believe that the owners of the cars should own the data, and we have concerns over the privacy implications of its use.

Overall, the NHTSA rule is a strong step forward in improving auto safety, one in line with our recommendations for improving U.S. automotive safety.


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