045-II Wyo. Code R. § 1.4
(1) Speed limits and speed zoning remain one of the more controversial tasks for the traffic engineering profession. Engineers, public safety officials, and others involved in setting and enforcing speed limits may disagree on the appropriate balance between safety and road-user convenience that should prevail on particular road segments, considering conditions of topography, weather, adjacent activities, and traffic. Motorists, other road users, and roadway neighbors have their own perspectives on this balance and may or may not abide by the professionals' judgments.
(2) In order for the regulation of speed to be effective, the posted limit must be generally consistent with speeds that drivers feel are safe and proper. Enforcement is widely recognized to be crucial to the success of speed limits as a means for making roads safer. If law enforcement officers and the courts are confident that speed limits have been developed on a reasonable basis, their enforcement of the limits will be more effective. Generally, speed limits should be set at levels that are self-enforcing so that law enforcement officials can concentrate their efforts on the worst offenders.
(3) For most cases, the recommended speed limit shall be the 85th percentile speed rounded to the nearest 5 mph.
(4) A professional engineer can consider the factors described in Section 1.2 to justify a lower speed limit. The recommended speed limit should never be below the lowest acceptable speed limit described in section 1.2(10).
(5) The recommended speed limit on unpaved roads shall never be higher than the statutory speed limit of 55 mph.
(6) Speed limit signs serve to remind motorists that conditions in the area are such that a reduction in speed is reasonable. Proper use of speed limit signs would instill confidence in the minds of drivers that the information on the speed limit sign is accurate and not simply a desire on the part of a policy maker to reduce speed arbitrarily.
(7) In cases where the speed limit is posted below the 85th-percentile speed based on the other factors, the speed limit sign serves to remind motorists that conditions in the area are such that the speed reduction is reasonable. Proper use of speed limit signs instills confidence in the minds of drivers that the information on the speed limit sign is accurate and not simply a desire on the part of a policy maker to reduce speed arbitrarily for emotional or political reasons.
045-II Wyo. Code R. § 1.4