ABSTRACT
This chapter gives the student of transportation planning with the operation and maintenance of transportation systems and facilities. Traffic-actuated signalization can involve semi-actuated, fully actuated, or volume-density control. The first requires vehicle detectors on one or more, but not all, approaches to an intersection. Individual signalized intersections can be interconnected to form systems. Urban arterial streets often are controlled to provide progressive traffic flow along the arterial. The most sophisticated signal systems are those in which entire networks are computer-controlled. Railway signaling and control, having evolved from the original use of policemen to modern, sophisticated, and complex systems, is a highly specialized technique and as such does not lend itself to other transport systems. The conventional block system is used with vital relays located both on-board and along the guideway. Two major requirements of rail and guideway transit are safety and reliability.
