Mo. Rev. Stat. § 304.181

The limitations on weight on axles established in section 304.180, do not apply to buses. No bus having a greater weight than twenty thousand pounds on one axle or thirty-four thousand pounds on any tandem axle shall be moved on or operated on any highway in this state. The terms "axle" and "tandem axle" as used in this section shall have the same meaning as is provided in section 304.180, for other vehicles.