The “Five-Minute Tunnel” will be back in business Saturday.

The one-way tunnel — controlled by traffic lights that make drivers wait five minutes — will reopen no later than 7 a.m. after $7 million in repairs were performed over the past six months, according to the National Park Service.

The 100-year-old tunnel, officially known as the Baker-Berry Tunnel, provides access to Rodeo Beach, the Marine Mammal Center and Capehart housing in Southern Marin. In the interim, a detour along Conzelman Road in the Marin Headlands brought visitors to those destinations.

“We continually work to improve visitor experience and to achieve both access and preservation,” said Golden Gate National Recreation Area acting superintendent Cicely Muldoon in a statement. “This project does both. We are very excited to reopen the tunnel just in time for summer.”

The road in the tunnel was redone with 900 tons of pavement.

“It will be a much smoother ride for bicyclists,” said Sonja Hanson, parks spokeswoman.

The antiquated lighting system in the tunnel was also replaced. The old lighting had used the second-most energy of any system in the entire park, behind district headquarters in San Francisco.

The old lights were replaced with a light-emitting diode, or LED, system. The LED ceiling lighting includes an energy management component corresponding to ambient light levels on the inside and outside of the tunnel. It will use 40 percent less energy.

The project also included preventative maintenance, water and sewer line replacement and general rehabilitation.

Work within the tunnel included 45,000 pounds of polyurethane resin injection to shore up fissures and cracks. The cracks and leaks resulted in a slippery film of mineral-laden sediment that created a safety hazard for vehicles and bicyclists.

During the winter rains, water could be seen flowing through cracks inside the tunnel.

In 1917 the U.S. Army began work on the tunnel, cutting through serpentine rock and putting up a timber structure. It was finished in 1918 with macadam surface and cobblestone gutters. It improved military communication and travel between Fort Barry on the Rodeo Beach side and Fort Baker closer to the Golden Gate.