Most Ford and General Motors vehicles and two new Chrysler models are equipped with black boxes, which can give details about the way you drive.

BLACK BOX INFO Find out if your automobile has a black box at www.airbagcrash.com. (Note: Scroll to bottom of page to find your auto model after you click on link.)

Opponents don't like it, arguing it's akin to Big Brother spying on drivers. Still others think it's an invaluable tool in accident reconstructions.

Mohammad Bazzi and his cousin were racing down Interstate 75 when Bazzi's vehicle rear-ended a semi-truck killing a passenger in his car.

Accident investigators were able to better pinpoint the speed by using a little-known data storage unit on the vehicle called a CDR or Crash Data Recorder.

It's part of an automobile's air-bag system and documents the speed, braking, acceleration and other data five seconds before the accident. It showed the pair of cars were going 95 miles per hour and led to a conviction of a death caused by a drunken driver.

Prosecutors are finding the black box a valuable tool.

"All of this information aids us not only in whether to charge someone and with what crime, but it's an invaluable piece of scientific evidence that juries love to hear before they convict somebody," said Dave Gorcyca, Oakland County prosecutor.

But the technology is raising concerns about civil liberties.

"We're concerned about the fact consumers don't know the black box is there. California passed a disclosure law saying the black box has been installed," said Wendy Wagenheim of the American Civil Liberties Union.

Local 4 showed drivers where the black boxes were in their cars. Some had a negative reaction.

"That's the same as me putting a camera in your house. It's an invasion of privacy," said Anthony Tillman.

Others saw the black boxes as positive.

"I think it's a good thing. It's the truth," said Neil Carpenter.

Ford and General Motors now disclose the presence of the black box in the owner's manual, but does anyone read it?

Federal safety officials want to make Big Brother bigger by increasing the amount of data recorded.

Sometimes the Big Brother black box can be a driver's best friend. In 2002, a woman crossed a center line on Drake Road in West Bloomfield. She was facing two years in prison for negligent homicide until prosecutors downloaded her car's black box.

They found she was travelling below the posted speed and that there was no evidence of increased speed. The conclusion? She hit a patch of ice. Charges were reduced.

"I believe it saved her from being convicted of very serious charges," said defense attorney Harold Fried.

Many people ask about disconnecting the black box. General Motors said that would be a bad idea, because it could degrade the air bag's performance.

Government safety officials want black boxes in all vehicles by 2008 with the ability to record 42 different functions.