Bus replacement service will be instituted along the length of its SPRINTER route, which normally operates between Oceanside and Escondido, Calif.

Worn brake rotors are the direct cause of the service disruption. Local media reported that NCTD Executive Director Matthew Tuckersaid the rotors "don't meet the standards of compliance," even though the light rail vehicles "are still safe to operate."

California's Public Utilities Commission identified the faulty rotors earlier this month during an inspection, according to Tucker. "They don't have the authority to shut us down," said Tucker, but NCTD decided to do so in the interest of safety.

SPRINTER service, the second DLRT line to begin U.S. operations, began revenue service in March 2008; it carries roughly 7,800 passengers per day.