WASHINGTON — Have a happy Fourth of July – but drive carefully. Independence Day is the deadliest day of the year on the road.

Not only is July Fourth ranked No. 1 for overall traffic fatalities – with an average of about 140 road deaths each year – it’s also the deadliest day for teen drivers and their passengers.

Teens make up nearly 10 percent of July Fourth traffic deaths, according to the AAA, which called on parents to restrict their driving privileges.

The warning comes on the heels of congressional approval of a transportation bill that would provide financial incentives to states that establish graduated licensing programs. Such programs impose restrictions on teenagers’ driving privileges.

Chris Mullen, director of technology research at State Farm, said that strong graduated licensing laws “gradually and systematically expose teens to more complex driving situations, ultimately reducing their crash risk. Studies show that crashes among teen drivers have decreased by up to 38 percent in states with strong graduated licensing systems.”

But Jonathan Adkins of the Governors Highway Safety Association expressed concern that Congress has set such strict requirements that few states may qualify for the grants.

Preliminary figures for 2011 indicate that overall traffic deaths declined to their lowest level since record-keeping began in 1949. However, teen drivers are of concern because the number of teens dying in car crashes last year appears to have increased for the first time in eight years.

An Insurance Institute of Highway Safety study of crashes between 2006 and 2010 ranked Independence Day as the deadliest day, with an average of about 140 deaths, followed by Sept. 26, about 129 deaths, and Aug. 2, with 125 deaths.

On the Fourth of July holiday, schools are out, offices are closed and more people are on the road, an institute spokesman said. Further, a higher proportion of deaths are related to drinking and driving on July Fourth than on a typical day, he said.

On July 4, 2010, 39 percent of traffic fatalities involved a drunken driver, compared with 31 percent normally, according to Mothers Against Drunk Driving.

The organization praised a provision of the new transportation bill that would offer financial incentives to states that crack down on distracted driving and require ignition interlock devices for drunken-driving offenders.