Miss. Code § 63-5-34
For the purposes of Sections 63-5-29 and 63-5-33, any motor vehicle measuring more than twenty-nine (29) feet between the extreme axles with title to such vehicle registered with the State Tax Commission in accordance with the provisions of Section 1 et seq. may use public highways, excluding the federal interstate highway system, and be considered as a motor vehicle with a distance between the extreme of any group of axles twelve (12) feet longer than the extreme measurement of any such group.
Any motor vehicle that measures more than twenty-nine (29) feet and less than or equal to forty (40) feet between the extreme axles whose gross weight does not exceed seventy-two thousand (72,000) pounds on four (4) axles or seventy-three thousand two hundred eighty (73,280) pounds on five (5) axles, with title to such vehicle registered with the State Tax Commission on or before April 24, 1974, and in accordance with the provisions of Section 1 et seq., may use the federal interstate highway system and be considered as a motor vehicle with a distance between the extreme of any group of axles twelve (12) feet longer than the extreme measurement of any such group.
The provisions of this section may be superseded by action of the Mississippi Transportation Commission, by resolution spread upon its minutes, for any specified segment of a state highway or bridge in accordance with the provisions set forth in Section 65-1-45, when, due to any special weather or other hazard, such highways or bridges have been weakened or when such highways have substandard surfacing or weak bridges due to any cause.
This section shall not apply to situations in which its application would create a conflict with any length regulation or weight restriction imposed by federal law on the federal interstate highway system.
Miss. Code § 63-5-34