(KRON) — Anyone who’s taken the Bay Bridge eastbound late at night in recent weeks may have had a slower-than-usual commute. Caltrans told KRON4 that won’t be changing anytime soon.

On the bridge going eastbound, two lanes are closed starting just after the final San Francisco entrance to the bridge up until the exit to Yerba Buena Island. The lanes are closed starting at 11:00 p.m. until 5:00 a.m. five nights a week — Sunday through Thursday. If necessary, another lane is closed at midnight.

Currently, the lanes are closed to install a sprinkler system in the Yerba Buena Tunnel. The system is designed to prevent fires from melting the structural elements of the tunnel.

Later in February, Caltrans will embark on another project. Work crews will replace rivets on the bridge with high-strength bolts, using the lane closures in place for the sprinkler system.

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“To kill two birds with one stone, as the saying goes, Caltrans will use the same closures for a seismic retrofit project that begins later this month,” a Caltrans spokesperson told KRON4.

Caltrans is aiming to finish the jobs in May but says it is too early to give a specific date in May.