When Timothy P. Murray crashed his Ford in 2011, he was fortunate. The lieutenant governor of Massachusetts was not seriously hurt, and he told police he was not speeding.
But a different story soon emerged. Murray was driving more than 100 miles an hour and was not wearing a seat belt, according to the computer in his car.
The case put Murray at the center of a debate over a piece of equipment: the event data recorder, or black box.
About 96 percent of vehicles sold in the United States have the boxes; if the National Highway Traffic Safety Administration has its way, all will.
The data identify safety problems and are used as evidence in accidents and crimes. But the trove of data has raised privacy concerns.