An Arlington Transit bus suffered an apparent brake malfunction and rolled down a steep hill on N. Barton Street this morning, coming to a stop half-way down the hill after it ran into a car.

The crash closed N. Barton Street between Fairfax Drive and 14th Street N. in the Courthouse area for more than an hour, as a heavy-duty tow truck was brought in to haul away the bus.

According the driver of one of the vehicles damaged in the crash, the natural gas-powered ART 45 bus started rolling back toward Fairfax Drive as it neared the crest of the hill. It rolled at least 10 feet before slamming into a black Lexus, which in turn rolled back into a Volkswagen minivan and a Reston Limousine bus.

The driver of the Lexus was transported to the hospital for evaluation, we’re told. The driver of the ART bus was shaken but not hurt. So far, no other injuries have been reported.

The crash may have prevented an even more catastrophic incident; had the other vehicles not stopped it, the bus could have gained speed as it rolled all the way down the steep hill.

Police and ART officials are investigating the wreck. An Arlington County spokeswoman declined to comment, saying the county would be releasing a statement later this afternoon.