Generally speaking, traffic control is the use of road-based devices to assist people, goods, and vehicles in moving from one place to another. These devices may be either physical (e.g., roadways, railroad tracks, and airfields) or electronic (e.g., radio and television stations, electronic signs, communications devices, and navigational aids).
Uniformity of devices simplifies road users' perception and reaction time, which reduces the amount of time it takes to recognize and understand a situation. It also makes highway operations, law enforcement, and the traffic courts more efficient in their work by giving everyone a common interpretation of what is expected from them.
Although some highway design features, such as curbs, median barriers, guardrails, speed humps or tables, and textured pavement, have a significant impact on traffic operations and safety, they are not considered to be traffic control devices. Hence, their provisions regarding their design and use are generally not included in this Manual.
Portable changeable message signs are designed so that they can be easily transported and reused at different locations. They are often used for traffic control purposes during construction, maintenance or other temporary activities that would otherwise require police control of the area in question.
The use of traffic control equipment to perform nonpolice temporary traffic control (beyond emergency closure) requires a permit from the local governing body, and a traffic management plan is required before permission is granted. These plans are governed by the Australian Standard AS 1742.3 - 2009, and State variations.