Eight out of 10 crashes in the United States involve drivers who are drowsy, chatting on a cell phone, applying makeup or otherwise distracted from the road ahead, according to a government study released Thursday that videotaped people behind the wheel.

Reviewing thousands of hours of video and data from sensor monitors linked to more than 200 drivers, researchers found that a wide range of distractions can lead to crashes or near-crashes.

Reaching for a moving object while driving increased the risk of a crash by nine times, while reading or applying makeup from behind the wheel enhanced the risk by three times. Dialing a cell phone, meanwhile, increased the risk of a crash by nearly three times, researchers found.

The project helped show what happens in the fractions of a second before a crash or near miss. Researchers said it showed the first links between crash risks and popular multi-tasking activities — from eating and talking to receiving e-mail in the driver's seat.

"All of these activities are much more dangerous than we thought before," said Dr. Charlie Klauer, a senior research associate at the Virginia Tech Transportation Institute.

For more than a year, researchers with the National Highway Traffic Safety Administration and the Virginia Tech Transportation Institute studied the behavior of the drivers of 100 vehicles in northern Virginia and metropolitan Washington, D.C., equipped with video and sensors. They tracked 241 drivers, who were involved in 82 crashes of various degrees of seriousness — 15 were reported to police — and 761 near-crashes.

Called the 100-Car Study, the massive research project analyzed nearly 2 million miles driven and more than 43,300 hours of data.

Drowsy driving increased the driver's risk of a crash or near-crash by four to six times, the study said. But the study's authors noted drowsy driving is frequently underreported in police crash investigations.

When drivers took long glances away from the road ahead of them at the wrong moment, they were twice as likely to get into a crash, the report said.

Some safety organizations cautioned that the study was among a growing body of research and worried that it might set off reactionary laws across the states.

"I urge legislators not to interpret these results as a need for new legislative initiatives. It is simply not good public policy to pass laws addressing every type of driver behavior," said Lt. Col. Jim Champagne, chairman of the Governors Highway Safety Association.