MARIETTA — Drivers on Canton Road at Cobb Parkway could see slowdowns beginning later this month.

State transportation officials have begun an $11.2 million project to replace the Canton Road bridge and an adjoining railroad bridge, both of which were built in 1938. Cobb Parkway underneath the bridge will also be widened and sidewalks installed, though the entire project won’t be finished for two years.

Atlanta Gas Light crews are in the process of relocating a 12-inch gas line, said Mark McKinnon, a spokesman for the Georgia Department of Transportation.

Once that is complete, which is expected by the end of this month, GDOT will limit traffic on the bridge to one direction at a time. Temporary traffic signals will be in place, and the lane limits could last for eight months.

McKinnon said the lane limits are necessary for construction of a new CSX railroad bridge. At some point, the bridge will be closed to vehicle traffic for a month while the railroad is realigned, he said. Drivers can use the Canton Road Connector as an alternate. Rail traffic will also be restricted.

“There will be a time when rail traffic will have to be stopped in order for the railroad company to tie in their existing line into the new alignment of the new bridge,” McKinnon said.

Drivers on Cobb Parkway will also be affected by construction. Once construction ramps up, one lane in each direction of Cobb Parkway will be closed from 9 a.m. to 3 p.m. Monday through Friday, to allow the contractor to cut back dirt alongside the highway.

A five-foot-wide sidewalk will be installed along Cobb Parkway under Canton Road, McKinnon said. Right now, there is no shoulder under the bridge, a fact that doesn’t stop pedestrians from walking along the road.

Canton Road, which will have two lanes in each direction when complete, will also get six-foot-wide sidewalks on both sides of the road, McKinnon said.

GDOT worked with the Marietta City Council and Mayor Steve Tumlin ahead of the project.

“It’s going to be a challenge, but it’s one we’re addressing the best we can to maintain safety and traffic flow,” Tumlin said.