In accordance with Louisiana state law, the speed limit in a residential or business district is 30 miles per hour (MPH) with or without the presence of a speed limit sign. Although not required, 30 MPH speed limit signs may be posted at entrances to residential or business areas. Multiple postings of 30 MPH speed limit signs on residential streets not only detracts from a neighborhood's curb appeal, but it often fails to achieve the desired result of reducing the speed of motorists.
Louisiana State Law allows local authorities to determine and/or change the maximum speed limit for all streets within their respective jurisdiction to a reasonable and safe speed based on engineering and traffic investigations. The Manual on Uniform Traffic Control Devices (MUTCD) published by the United States Department of Transportation and the Federal Administration Highway is the national set of standards for traffic engineering. The MUTCD recommends that the following six factors be evaluated to establish safe and reasonable speed zones:
- Roadway characteristics such as shoulder condition, grade, alignment, and sight distances.
- Speed characteristics such as the 85th percentile speed.
- Roadside development and friction.
- Roadway curves and hazardous locations on and along the roadway.
- Parking and pedestrian activity.