RESEARCH TRIANGLE PARK — Work crews have reduced I-40 east at Davis Drive to two lanes again while they work on the temporary construction barriers that were damaged in an early morning accident that slowed traffic for hours.

A tractor-trailer was traveling on the interstate around 4 a.m. when it veered into the concrete guards.

Highway Patrol officials say the vehicle bounced off the barriers, and witnesses later saw the trailer flipped on its side.

The single vehicle accident left the driver shaken, but not injured.

Traffic was reduced to one lane at the Davis Drive merge for much of the morning.

At one point, cars were backed up about 13 miles west of the Davis Drive exit, to the Durham-Orange County line.

Frustrated drivers wonder why it took so long to reopen the lanes.

DOT officials say crews had to wait for a wrecker from Greensboro that was big enough to move the rig.

"It's one of those things you have to learn in life, it's one of the unfortunate things that happen. But when you've got so many commuters driving on one road, and everybody's got but so much room and so many lanes to go on, this is what happens," said DOT engineer Jerry Linder.

"You've just got to be patient and handle it," Linder said.

Linder also encouraged commuters to watch for reports and take alternate routes as possible.