Requirement #1 - Fulfill a Need
A traffic control device must be proven to fulfill a need. The determination of when certain traffic control devices are needed is an engineering decision and should only be made by a qualified engineer. The traffic engineer responsible for such action must know the situations for which various types of traffic control devices are warranted.
The engineer should collect the necessary traffic volume, pedestrian, speed, and crash data; measure the geometric features; and observe vehicle behavior at the location of interest.
This information should be investigated to determine if the location and conditions meet MUTCD requirements. If the requirements are not met, the traffic control device should not be installed.
Roadway geometric design and sign application should be coordinated so that signing can be effectively placed to give the road user any necessary regulatory, warning, guidance, and other information. Results from traffic engineering studies of physical and traffic factors should indicate the locations where signs are deemed necessary or desirable. It is only these signs that are justified by engineering judgment or studies that should be installed. In all cases, the minimum-required signage to achieve safe and efficient traffic operation should be used.
Several publications exist to help determine the need for traffic control devices.