Mo. Rev. Stat. § 300.105: Operation of vehicles on approach of authorized emergency vehicles.

1. Upon the immediate approach of an authorized emergency vehicle making use of audible and visual signals meeting the requirements of the laws of this state, or of a police vehicle properly and lawfully making use of an audible signal only the driver of every other vehicle shall yield the right-of-way and shall immediately drive to a position parallel to, and as close as possible to, the right-hand edge or curb of the roadway clear of any intersection and shall stop and remain in such position until the authorized emergency vehicle has passed, except when otherwise directed by a police officer.

2. This section shall not operate to relieve the driver of an authorized emergency vehicle from the duty to drive with due regard for the safety of all persons using the highway.