Charleston County has the most substandard bridges in the state, but the situation poses no immediate risk to the traveling public, according to AAA Carolinas.

The county topped the list with six bridges among the top 20 substandard bridges. Richland and Lexington counties each had three bridges in the top 20 of AAA’s list.

“All South Carolina open bridges are safe for use by the motoring public within whatever restrictions are posted,” said Secretary of Transportation Robert St. Onge.

The Charleston County substandard spans include the heavily traveled drawbridge over Wappoo Creek and the S.C. 7 bridge over the Ashley River in North Charleston, according to AAA Carolinas.

A 54-year old bridge in Richland County carrying more than a half-million vehicles weekly is rated South Carolina’s top substandard bridge for the 11th time, according to AAA Carolinas.

The I-26 bridge that passes over C.N. and L. Railroad, three miles northwest of Columbia, has topped the list every year except one since 2000.

The percentage of South Carolina bridges rated substandard decreased from 23 percent in 2011 to 20 percent this year. There currently are 1,880 substandard bridges in the state.

Substandard bridges officially are classified under federal guidelines as “structurally deficient” or “functionally obsolete” with AAA Carolinas assigning extra weight to traffic volume to highlight bridges affecting the most motorists.

“Structurally deficient” is defined as being in relatively poor physical condition and/or inadequate to handle truck weight.

“Functionally obsolete” is defined as having inadequate design for current traffic volume. States inspect bridges to determine their condition and qualify for federal aid replacement funds when a bridge scores less than 50 on a 100-point scale.

The state estimates that bridge maintenance, repair and replacement needs for bridges costs roughly $200 million a year. South Carolina’s gas tax is the main funding supply for the Department of Transportation and has been unchanged since 1987.

South Carolina has a lower percentage of substandard bridges than neighboring North Carolina’s 32 percent, but other Southeastern states, including Tennessee (14 percent) and Georgia (14 percent), have done a better job addressing their bridge and road needs, according to AAA.