Much of the morning rush hour was slow for thousands of commuters yesterday after a semitrailer truck jackknifed on the Capital Beltway near the American Legion Bridge, closing the Beltway's inner loop for about three hours.

Although it occurred about 3:30 a.m., the accident illustrated how a single accident can foul up rush-hour traffic on the Beltway. All lanes were reopened by about 6:45 a.m., authorities said.

Maryland State Police said a semitrailer truck carrying furniture was heading into Maryland on the Beltway near the George Washington Memorial Parkway, where a construction project has narrowed the Beltway to a single lane at that time of the day.

The driver, Robby Mills, 36, of Mississippi, apparently saw a construction worker on the road, police said. After Mills swerved, the truck hit a construction crane, a parked car and a concrete barrier. Diesel fuel spilled from a ruptured fuel tank.

Mills was charged with failure to stay in a single lane.

While the inner loop was closed, a car heading into Virginia on the outer loop slammed into a fire truck that had responded to the accident. That contributed to the delay, authorities said. There were no serious injuries in either accident.