S.C. Code § 56-5-3880
The Department of Transportation may close state highways, roadways, or bridges to allow marathons or other running events when the race or event is open to all persons including the handicapped if in the opinion of the district engineer the race or event may be conducted in a safe manner. The Department of Transportation, city, county, organization, and sponsors of the race or event are immune from liability except for gross negligence from incidents arising from participation in or association with the race or event.
If the John P. Grace Memorial Bridge is not available for the annual Cooper River Bridge Run and Walk in Charleston County, the Silas N. Pearman Bridge must be made available for the event, if a contingency plan for vehicular traffic can be developed, provided, that if the Cooper River Bridge Run and Walk is not open to persons sixty-five years of age or older, neither bridge may be used for this event.
S.C. Code § 56-5-3880