The need for minimum speed limits should be determined through an engineering and traffic investigation. When such a speed is justified, it should be regulated in the same manner as maximum speed limits are regulated.

Minimum speed limits are generally justified when studies show that slow moving vehicles on any part of a highway consistently impede the normal and reasonable movement of traffic to such an extent that they contribute to unnecessary lane changing or passing maneuvers.

The maximum speed limits and the need for minimum speed limits must be determined from the same speed check data. , contains a discussion of the 85th percentile speed and minimum limits.

MINIMUM SPEED LIMIT signs (R2-4) shall be displayed in conjunction with and beneath the MAXIMUM SPEED LIMIT signs (R2-1) or as an integral sign (R2-4a).