The downtown Seattle bus tunnel will remain closed at least through Thursday while a computer glitch is fixed, said Kevin Desmond, general...

The downtown Seattle bus tunnel will remain closed at least through Thursday while a computer glitch is fixed, said Kevin Desmond, general manager for King County Metro Transit.

The tunnel closed this morning about 5 a.m. due to problems with a computer system that would help officials control tunnel operations, such as signals, ventilation, elevators, security cameras, and lights, in the event of an emergency. It was the second closure this week.

All routes that usually go through the tunnel are running on the street.

Metro suggests riders check printed timetables or its Web site, www.kingcounty.gov/metro, for their route numbers and check under the heading “When the tunnel is closed.” Riders on the Sound Transit 550 express bus, to Bellevue, can get updates at soundtransit.org.

Desmond said buses have been moving well on the streets so far this afternoon, in part because of relatively light holiday traffic.

There is no estimate for when the computer system will be up and running again, but replacement parts may arrive tonight, said Ahmad Fazel, light-rail director for Sound Transit.

All of the systems in the tunnel are controlled by a computer system installed during the recent retrofit of the tunnel. “We have to be assured we can remotely operate all the emergency systems if we need to,” but that’s not possible today, said Metro spokeswoman Linda Thielke. So Metro opted to close the tunnel instead. “We need to err on the side of caution,” she said.

The tunnel handles 1,076 bus trips on 18 routes on a typical weekday.

Sound Transit recently completed a two-year, $86 million retrofit, including new pavement and rails, to prepare the tunnel for light-rail trains to mix with buses in late 2009.

The tunnel closed Monday afternoon because of a computer glitch, and reopened early Tuesday.