Event data recorder (car black box)

In plain English: an event data recorder, or EDR, is a device in most modern cars that saves a few seconds of driving data around a crash, such as speed, braking and whether seatbelts were buckled.

What it can record

• Vehicle speed in the seconds before impact
• Whether the brakes or accelerator were applied
• Steering input and engine speed
• Seatbelt use and airbag deployment timing
• The change in speed during the crash (delta-V), which helps show crash severity

In the US, federal rules standardize what's recorded if a manufacturer installs an EDR, and most new passenger vehicles have one. Heavy trucks often have separate engine modules and telematics that record even more.

Why it matters

EDR data can settle arguments about speed and braking that witnesses disagree on. It can also cut both ways: it may show you were speeding. That's a good reason to get advice before sharing it.

Who owns the data

In the US, the federal Driver Privacy Act of 2015 says EDR data generally belongs to the vehicle's owner or lessee, and others usually need consent or a court order to access it. Rules differ elsewhere, and insurers who take ownership of a written-off car may try to control the vehicle.

Related: accident reconstruction · dashcam footage.

Related terms