Traffic Information and Control Systems

Traffic Control Systems

The traffic signal, even if it is a simple road sign at an intersection, impacts virtually everyone every day. Individual traffic signals, if implemented and followed out properly, achieve networkwide traffic operations objectives, which consist of intersection traffic signals, a communications network to tie them together, and a central computer or network of computers to manage the system. Techniques to monitor such systems include time-base and hardwired interconnection methods. Coordinating these methods across agencies requires data sharing and agreement upon traffic signal controls.

Roadway traffic control systems are intended to improve safety, increase the operational efficiency and capacity of the roadway, and contribute to the traveler's overall comfort and convenience. The areas monitored begin small at isolated intersections using signs and markings, and expand to sophisticated traffic control centers, which have the ability to react to changes in the traffic environment. Traffic control systems are used at roadway intersections, on highways and freeways, at ramp entrances to freeways, and in monitoring and controlling wider-area transportation networks.

People accept and even demand traffic signals to ensure safety and mobility. Drivers usually assume that the responsible agency can efficiently operate signals, such as traffic lights, so motorists usually report only the most obvious failures. Inefficiencies can cause longer trip times and higher fuel costs.

Research and applications demonstrate the effectiveness of signal system improvements in reducing delays, stops, fuel consumption, emission of pollutants, and accidents. Certain traffic systems have been termed adaptive, as in they have the ability to alter signal timing in response to both short-term and longer-term variations in traffic. These systems not only provide more effective control of traffic but also require fewer human and financial resources to update the system's database.

Road traffic controls are monitored by the Federal Highway Administration (FHWA), although state and local agencies have their own variations of standards set forth by the Manual on Uniform Traffic Control Devices (MUTCD). Traffic controls vary extensively throughout the United States, depending on the type of roadway being traveled and the kind of vehicles passing through. For this reason, consistency in traffic control certification is not found throughout the nation. For instance, the FHWA does not address certification methods for traffic controllers, flaggers, and other traffic personnel because this is deemed a state or local responsibility. Safety is measured by the Occupational Safety and Health Administration (OSHA) and state safety departments.

Other Modes of Transportation

The U.S. federal government has designated airspace as uncontrolled or controlled. In uncontrolled airspace, pilots may conduct flights without specific authorization, such as private pilots or those using recreational aircraft. In controlled airspace, pilots may be required to be in communication with an air traffic control facility to receive instructions on when they may pass, land, or take off.

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