No limitation shall be established by any county, municipal or other local authority pursuant to the provisions of § 56-5-4210 that would interfere with or interrupt traffic as authorized hereunder over state highways, including officially established detours for such highways and cases where such traffic passes over roads, streets or thoroughfares within the sole jurisdiction of such county, municipal or other local authority, unless such limitations and further restrictions shall have first been approved by the Department of Transportation, except that with respect to county roads, other than such as are in use as state highway detours, the respective county road authorities shall have full power and authority to further limit the weights of vehicles upon bridges and culverts upon such public notice as they deem sufficient, and existing laws applicable thereto shall not be affected by the terms of this article.