For a speed limit to be effective, at least 85 percent of the drivers must voluntarily comply with the law. It is important to remember that the speed regulation informs the driver of the limits in which one can safely operate a vehicle under normal circumstances and within which the driver can be expected to react safely. Setting speed limits at appropriate levels will create a reasonable uniform flow of traffic, discourage violation of the law and help keep streets and highways safe.
The DOT criteria for setting speed zones are presented in the publication entitled "Speed Zoning for Highways. This publication indicates "The 85th percentile speed is the speed at or below which 85 percent of the observed free flow vehicles are traveling." It also states that a speed limit should not differ from the 85th percentile speed by more than 3 mph and-it shall not be more than 8 mph less.
The following excerpts were also taken from the DOT Speed Zoning publication:
Louisiana Revised Statutes 32:64 deals with unlawful speed. This law states that "No person shall drive a vehicle on a highway at a speed greater than is reasonable and prudent under the conditions and potential hazards then existing, having due regard for the traffic on, and the surface and width of the highway, and the condition of the weather, and in no event at a speed in excess of the maximum speeds established"
City of Monroe Code Sections 33.5 and 33.45.1 authorize the Traffic Engineer to set speed limits for travel over roadways under his authority as he deems necessary to regulate and guide traffic. Section 33.45.1 also states that "No person shall operate a vehicle in excess of twenty-five (25) miles per hour upon any street, avenue or roadway within the city limits, unless a posted speed limit has been established, in which event the posted speed limit shall prevail."