An inexperienced driver who reaches for a cellphone increases the risk for a crash by more than 700 percent, a new study found.

Using accelerometers, cameras, global positioning devices and other sensors, researchers studied the driving habits of 42 newly licensed 16- and 17-year-old drivers and 167 adults with more experience. The machines recorded incidents of cellphone use, reaching for objects, sending text messages, adjusting radios and controls, and eating and drinking.

Among the teenagers, eating almost tripled the risk for a crash, and texting or looking at an object on the side of the road quadrupled it. Dialing a phone was the most dangerous activity of all, resulting in eight times the risk for a crash or near-crash.

For experienced drivers, only dialing a phone significantly increased the risk for an accident.

The study, published in The New England Journal of Medicine with an entertaining video, found that over all, drivers spent about 10 percent of the time looking at something other than the road in front of them.

“When young people engage in tasks that take their eyes away from the roadway, they’re increasing their risk dramatically,” said the lead author, Charlie Klauer, a research scientist at Virginia Tech University. “Kids need to have their eyes forward. To add any other distraction into this is really increasing the risk.”