Mo. Rev. Stat. § 304.172: Fire-fighting equipment exempt from size restrictions.

The provisions of sections 304.170 to 304.240 relating to height, width, and length restrictions for motor vehicles shall not apply to any motor vehicle and its attached apparatus which is designed for use and used by a fire department, fire protection district or volunteer fire protection association or when being operated by a fire apparatus manufacturer or sales organization for the purpose of sale, demonstration, exhibit, or delivery to a fire department, fire protection district or volunteer fire protection association.