Work has begun on a $400,000 replacement of the rusted, dented and unsightly steel box beam guardrail on U.S. 27 between the Olgiati Bridge and Signal Mountain Boulevard.

The night-time repair work started Friday, and contractors on the project have about 30 days to replace the guardrail with cement barriers, Tennessee Department of Transportation officials say, though the work is moving ahead of schedule.

“The old steel guardrail served its purpose, but it is definitely time to replace it with something newer,” said TDOT Regional Director Bob Brown. “We are very pleased that this project is under way and look forward to its completion.”

Repair work starts around 8 p.m. each day and TDOT is warning motorists of the lane closures, which will last for least a few more weeks. The work is going to cause traffic slowdowns and some congestion, though the night-time schedule is meant to reduce those delays, officials said.

Transportation officials have said the old guardrail, while ugly, was not a safety risk. Each segment of the railing weighs 1,200 pounds and keeps northbound traffic from entering southbound traffic, but it also created repair issues, said Jennifer Flynn, a TDOT spokeswoman.

Every time the railing needed a fix, a crane had to be brought in and traffic had to be diverted, she said. Motorists agreed the guardrail was an eyesore, but one traveler said she knows first-hand it can take a licking.

“I remember riding to downtown in the rain and sliding right into that railing,” said Vicky Bonner, a Hixson resident. “It scratched up my car pretty good. It looks like a lot of people did that over the years.”

By Monday evening, crews from Dement Construction Co. of Jackson, Tenn., had placed most of the new cement divider, but Ms. Flynn said workers need more time to straighten the concrete sections and perform finishing work.

The cement sections are temporary, however. U.S. 27 is scheduled for widening, and when that project is funded and starts the cement guardrail will be removed and used elsewhere. There is no timetable yet for the widening, Ms. Flynn said.