You probably have one stretch of road that you often drive where the posted speed limit seems too slow. You may wonder why officials do not just raise it to a more realistic speed, especially if everyone speeds down it anyway. The reality is that a lot of research, time and effort goes into creating the speed limits for each roadway. 

According to the Arizona Department of Transportation, before setting a speed limit there is an investigation. The state using a concept known as speed zoning. This is where officials analyze traffic and set speed limits that adhere to the speed of 85% of the drivers. For example, if on a roadway, most people, about 90% drive 35 MPH, then an investigation would discover that the speed limit for that roadway should be 35 MPH. 

However, other factors may come into play that will either increase or decrease that speed limit. Investigators will also consider other factors, such as accident rates on the road, the potential for development in the area and traffic volume. This is to ensure that the speed limit set is appropriate and safe. 

If a roadway happens to have new businesses or homes being built adjacent to it, then a lower speed limit may be necessary to accommodate future traffic patterns. A good case for lowering a speed limits from the speed zoning result is a high number of accidents. This shows the majority of drivers are wrong in thinking it is okay to drive the speed they are and need a limit set to help them drive safer in the area.