Overnight travel on the southbound Ashley River bridge connecting Charleston and West Ashley will be restricted starting Tuesday.

The bridge that takes commuters to West Ashley will remain open, but the right lane will be closed from 9:30 p.m. to 5 a.m. on Tuesday through Thursday and on Aug. 18-19.

The lane closure is necessary to complete work on the bridge, said Kevin Turner, a bridge engineer with the state Department of Transportation.

"We're doing it during low traffic volume time," Turner said.

The work is related to maintenance of machinery that raises the drawbridge, which is currently working fine, he said.

A twin span that takes traffic into Charleston is not affected.

Barricades, cones, signs and flashing arrows will be utilized for the southbound bridge work, and signs will identify the closure. The public is asked to use caution while driving through the area.

Charleston County has been ranked as having the highest percentage of substandard bridges in the state, with the worst of the bunch being the twin drawbridges over the Ashley River, according to AAA Carolinas.

The bridges are classified as functionally obsolete and structurally deficient, but officials have said that they are safe for traffic.

"Structurally deficient" is defined as being in relatively poor physical condition and/or inadequate to handle truck weight. "Functionally obsolete" means having inadequate design for current traffic volume, according to AAA Carolinas.

Reach Prentiss Findlay at 937-5711.