Abstract:Traffic control is a critical element in the safe and efficient operation of any transportation system. Elaborate operational procedures, rules and laws, and physical devices (e.g., signs, markings, and lights) are but a few of the components of any traffic control system. At the centre of any system is the operator: a driver or pedestrian in a roadway system, a pilot in aviation or maritime systems, and a locomotive engineer in railway systems. While traffic control can be considered initially as a need to control or influence large numbers of vehicles, it is important to realize that traffic is made up of a large number of individual operators who collectively must make consistent decisions in order for the systems to work safely and efficiently.

Safety is not the exclusive concern of the traffic control community. Nearly every transportation mode has organizations that regulate operators through a series of licensing procedures, sanctions for inappropriate operating practices, and requirements for continuing training to retain certification to operate. Examples include federal aviation authorities that oversee pilot training (e.g., the U.S. Federal Aviation Administration); road agencies that administer driver's licenses may exist at the provincial level (as in Canada) or at the national level (as is more common in Europe). Transportation safety management is thus accomplished through a complex set of interactions between different agencies at different levels (e.g., national, regional or state, and local) using both formal legal requirements and administrative actions. The following discussion will necessarily focus on safety concerns that evolve from and are a component of the traffic control function.