The North Bay's largest transit agency plans to spend $900,000 to replace and upgrade its bus fleet's surveillance cameras, many of which may not work.

The Golden Gate Bridge, Highway and Transportation District's board of directors plans to vote Friday on a plan to install new cameras on 80 Golden Gate Transit buses where the devices are considered obsolete.

"They don't work reliably, unfortunately," bridge district spokeswoman Priya Clemens said. "Sometimes they malfunction and we don't always know which camera is not working at any given time until the bus is pulled into our lot and we're able to do a system's diagnostic check."

On Thursday, the district's Transportation Committee approved the proposal, which also calls for upgrading technology on newer surveillance systems on the rest of the system's bus fleet.

The board's vote comes six months after a controversy erupted involving dummy security cameras on BART's train cars.