I heard about this recently....there was a Nevada Highway Patrol officer that hit a car on the 15 freeway here in las Vegas. He killed 3 of the 4 people on board. The police dept took the black box out of his 2004 Crown Victoria and sent it to Detroit for analasis. The outcome was the black box said he was going 112 mph just before he hit the car, and therefore was speeding and he was at fault because he didnt have any emergency lights on or was going to any emergency. He was convicted of 3 counts of man slaughter and was sentenced to 5-20 years in prison. So, if this is true about the black boxes, it can give some info about how fast you were going just before an accident.