TRAFFIC SIGNAL SYSTEMS: ADDRESSING DIVERSE TECHNOLOGIES AND COMPLEX USER NEEDS

In the next millennium, traffic signal systems will need to address many issues. New technology, such as traffic-responsive closed-loop 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. This paper reviews recent developments in microprocessor-based traffic signal systems to set the context for anticipated developments in traffic signal systems during the next millennium.