Legislation aimed at protecting California motorists from “black box” data went into effect on July 1. Black boxes, or event data recorders, are similar to those found in airplanes and have been installed in some cars as early as the ’70s, though only recently have crash investigators been able to retrieve and analyze the data. Now almost all new vehicles come installed with black boxes.The law, the first of its kind in the nation, prevents the recorded data from being obtained by police or others without the vehicle owner’s consent or a court order, except in cases of safety research in which the owner’s identity is protected. The law also requires automakers to disclose the presence of the devices in the owner’s manual.The devices measure five important factors in airbag deployment and near deployment events: vehicle speed, engine speed, brake status, throttle position, and the position of the driver’s seat belt switch (on or off). The data is stored from five seconds before a crash.Black box data has already been used as evidence in trial. A Florida man was sentenced to 30 years in prison for vehicular manslaughter after the black box in his 2002 Pontiac Trans Am said he was traveling between 104 and 114 mph before a deadly crash that killed two teens. But legislators and privacy advocates caution that the data isn’t infallible.Robert Breitenbach, the director of the Transportation Safety Training Center at Virginia Commonwealth University, knows this from firsthand experience. His team studied an accident involving a Cavalier in which the EDR data said that the brakes weren’t applied at all prior to the crash. But the physical evidence—hot shock was found in the brake lamp filament—clearly showed that the driver had braked. The conclusion was that the black box had either malfunctioned or the data was corrupted after the crash.