A flatbed truck carrying construction equipment struck the underside of the Capital Beltway while traveling on Rte. 50 in Fairfax County yesterday afternoon, causing an estimated $250,000 damage and forcing the closure of a Beltway access lane for at least 30 days, officials said.

The accident, which caused no serious injuries, occurred about 2 p.m. in an eastbound lane of Rte. 50 when a crane on the flatbed failed to clear an elevated portion of the outer loop near Merrifield. After surveying the damage, highway engineers closed off the outer lane of the Beltway access road and issued an emergency appeal to area contractors for bids on repairing the bridge, according to a spokeswoman for the Virginia Department of Transportation.

The driver, identified as Steven James McNab, 27, of Falls Church, will be charged with carrying a load in excess of height restrictions, according to Virginia Trooper Marc Quince. He said the crane exceeded the 14-foot, five-inch bridge clearance by at least a foot.

McNab was taken to Fairfax General Hospital with minor injuries, according to Quince.

The truck and construction equipment belong to a McLean rental company and were on the way to a construction site in Falls Church when the accident occurred, Quince said.

The impact cracked a concrete bridge support, twisted a steel I-beam and cracked the bridge surface, according to Marianne Pastor of the Transportation Department. She said, however, that structural damage was confined to the access road and would not affect traffic on the Beltway.

At Rte. 50, the outer loop of the Beltway is served by a two-lane access road for cars entering and leaving the highway. Motorists will have to make do with one lane until the damage is repaired, Pastor said.

"We hope to have the repairs completed within 30 days, although it could take longer," she said.

The accident tied up traffic on eastbound lanes of Rte. 50 for more than three hours yesterday.