Traffic Signal Systems: Addressing Diverse Technologies and Complex User Needs

In the next millennium, traffic signal systems will need to address many issues, spanning a broad range of technical, social, and political boundaries. With the increase in urbanization and traffic congestion comes a greater demand to operate our roadway systems with maximum efficiency. As traffic volume continues to increase, roadway capacity will increase at a slower rate. New technology, such as traffic-responsive closedloop systems or adaptive traffic signal systems using advanced surveillance and traffic management centers, will become increasingly critical for city, county, and state organizations to meet transportation needs. Such systems depend heavily on field infrastructures such as vehicle detection, distributed microprocessor-based control systems, and near real-time interaction over diverse communication media. It is critical to have all of these elements operating in a stable, well-maintained environment, even during maintenance and construction. This is particularly challenging given the diversity of government agencies often responsible for different portions of what motorists perceive as a single transportation system. Each government agency typically has traffic-signal control technology of varying vintages and different procedures for operating traffic signal systems. Signal system operation is even further complicated by the recent trend that views traffic signal systems as a small component of an integrated multimodal transportation system. When such a perspective is adopted, the “customers” of traffic signal systems are much more diverse than just automobile drivers and require a high degree of agency cooperation.