TANA—An operating surveillance system for highway traffic control

A complete surveillance and traffic control electronic system was designed and is being put into operation in a newly built urban tollway in Naples, Italy. In this system, named TANA after the tollway name (TAngenziale di NApoli), information is collected from several hundred loop detectors placed along the highway (on each lane every 250 m) and is relayed to a Central Control Room, where it is processed in real time by a digital computer. As a result, traffic conditions are continuously displayed to operators, and useful information is given to motorists through automatically steered variable-message signs, which on the tollway display conditions of traffic ahead, conditions of the roadway, state of traffic on the exit ramps, and outside the tollway, information on the state of entrance ramps and on the conditions of traffic in given sections of the tollway. Strategies for the automatic incident detection carried out by the system are described. The main purposes of TANA system are the achievement of maximum safety in critical points such as tunnels and entrance ramps (where access is controlled by means of automatically steered tunnel controllers and ramp controllers), the decrease in number and importance of multiple accidents, the optimization of traffic flow in the tollway and in the interchanges with the urban network, and the possibility for the users to take educated decisions based on the knowledge of traffic conditions. Safety features are assured even in case of a fault in the central computer or in the telecommunications system, by means of local analog devices, operating in standby.