The number of teens and young adults talking on a cell phone while driving went up again last year, according to U.S. government research released on Tuesday.

A National Highway Traffic Safety Administration survey found that hand-held cell phone use among drivers between the ages of 16 and 24 increased to 8 percent in 2004 from 5 percent in 2002. The rate had stood at 3 percent in 2000.

The rate of cell phone use for drivers of all ages was the same 8 percent. At any given moment in the United States last year, an estimated 8 percent of all motorists, or about 1.2 million drivers, were talking on cell phones while behind the wheel, the survey found.

That compared to 6 percent in 2002 and 4 percent in 2000.

The study was conducted at 1,200 sites last June and July and involved roadside observations and, in some cases, telephone surveys. The age ranges in many cases are estimates.

The National Transportation Safety Board has recommended that novice drivers be prohibited from using cell phones while at the wheel.

The recommendation followed the death of a young Maryland driver who was involved in a fatal crash while talking on her cell phone.

University of Utah researchers found last month that teenagers and young adults on the phone while operating a driving simulator reacted as slowly as elderly drivers who were not using a phone.

New York, New Jersey and Washington, D.C., prohibit drivers from using cell phones without hands-free technology. A law banning drivers 18 and younger from using any type of cell phone is working its way through the Virginia legislature.