Mo. Rev. Stat. § 324.724: Alternate route used, when.

Irrespective of the route shown on the special permit, an alternate route will be followed:

(1) If directed by a peace officer;

(2) If directed by a uniformed officer assigned to a weighing station to follow a route to a weighing device; or

(3) If the specified route is officially detoured. Should a detour be encountered, the driver shall check with the department of transportation prior to proceeding.