MOUNT PLEASANT -- Driving on congested Johnnie Dodds Boulevard is about to get slower.

The busiest highway in town will have a new speed limit -- 35 mph.

Increased safety for construction workers and motorists is the reason for the change, Charleston County said in a statement released Thursday.

Reduction of the 45-mph speed limit, which begins Oct. 13, will last until widening of the road is finished late next year, officials said.

The road is a construction zone for three miles from the Arthur Ravenel Jr. Bridge to Interstate 526. It is being widened from four lanes to six in an $80 million Charleston County Roadwise project.

"Motorists traveling on U.S. 17 need to watch their speed," the county said.

Crews will begin removing the old speed limit signs and installing new ones. The county warned that motorists who get caught driving too fast could be fined up to $450.

Alternative routes to the boulevard are recommended if possible. The road-widening project is intended to relieve rush-hour gridlock.

The biggest flurry of road construction is happening where a Bowman Road overpass is being built.