In san antonio, limited funds precluded the traditional approachto a consultant-designed urban traffic control system (utcs) for traffic signal control in the downtown area. By applying principles now common in other parts of the computer industry, san antonio engineers were able to formulate an alternative to the traditional approach that not only provides very substantial improvements in cost-effectiveness, maintainability, and reliability, but also provides the end user with complete access to the inner workings of the system. Emphasis on conforming to computer-industry standards of system design and commitment to open hardware and software architecture allowed full portability of software. Highly distributed processing greatly reduced the communications overhead while improving operation comparedwith other large-scale systems currently in operation in the unitedstates. The san antonio system has full-featured capabilities, including planned traffic-responsive operation, and uses one-tenth of the usual communications overhead without using a machine larger than a microcomputer. A comparison is made with a recent utcs project. This paper appears in transportation research record no. 1324, Communications, traffic signals, and traffic control devices 1991
Abstract