A fleet of natural gas-fueled shuttle buses that ferried travelers at Baltimore-Washington International Airport for nearly eight years has been pulled from service after the fourth bus fire in nine months.
In two of the incidents, drivers and passengers on the buses escaped injury, but more than a dozen vehicles parked nearby were damaged or destroyed.
The most recent incident occurred at BWI's lower-level passenger pickup area on May 8, when an emergency brake system failed and caused a minor fire, BWI officials said. Investigators concluded that the fire was unrelated to the others. But shuttle operator Hudson General LLC was concerned enough to suggest replacing the buses, officials said.
"We concurred," said Jennifer Cassidy of the Maryland Aviation Administration. "There were four instances, and we just decided it was in the interest of safety until we could have more information."
The 18 shuttles, fueled by compressed natural gas, were pulled the same day. Standard buses have replaced them, and Cassidy said she doubts the original fleet will be put back in service. The switch did not interfere with service, she said.
Officials at Hudson General did not return several phone calls requesting interviews yesterday.
The first fire, in the B parking lot on Aug. 10, forced the driver and five passengers to bolt from the bus, which was consumed by flames within two minutes. The fire destroyed the bus and three cars parked nearby, and damaged eight other vehicles.
On Dec. 23, another fire broke out in the same lot, with similar results: passengers fleeing and eight cars damaged or destroyed. Both fires appeared to have begun in the engine, but damage to the buses was so extensive that investigators were unable to pinpoint the cause.
They concluded, however, that the natural gas did not contribute to the start of the fire.
"The cause was some sort of mechanical failure, but that's our only information," said Allen Gosnell of the state fire marshal's office.
A small electrical fire broke out in a bus on Nov. 2, causing minor damage. No passengers were on the bus, and the driver managed to get it safely back to the garage.
After the December incident, Hudson designed a new fuel delivery system and fit each vehicle with a fire suppression system.
"There was no compressed natural gas involved in the latest fire," Cassidy said. "The retro systems they put in worked fine."