A small electronic device built into many vehicles records brief, crash-related information such as speed, braking, seat belt use, throttle position, and changes in force just before, during, and sometimes after a collision.

Often called a vehicle "black box," an event data recorder does not capture everything that happens in a car and usually does not record long stretches of driving. Instead, it preserves a narrow snapshot that can help explain how a crash unfolded. For example, the data may show whether a driver braked hard before impact, whether the airbags deployed, or how fast the vehicle was traveling seconds earlier. In accident reconstruction, that information is compared with skid marks, vehicle damage, witness statements, and surveillance footage to test competing versions of events.

For an injury claim, recorder data can strongly affect questions of liability, comparative fault, and damages. In Hawaii, that matters because the state follows modified comparative fault with a 51 percent bar: under Hawaii Revised Statutes § 663-31 (2024), an injured person cannot recover damages if they are found more than 50 percent at fault. Data showing sudden braking, no braking, or rapid acceleration can shift that fault analysis. On congested roads such as the H-1 Freeway, where chain-reaction collisions are common, recorder evidence may help separate one driver's actions from another's and support or challenge an insurer's or expert's reconstruction.