1. Functions

The traffic signal monitoring system is the primary system of an expressway monitoring system. By collecting real-time changing road traffic flow information (including traffic information, meteorological information, traffic abnormal event information, etc.), road and monitoring facility status information, and other such information, it judges whether traffic operation status is normal, predicts abnormal traffic operation status, confirms the severity of traffic abnormal events, and proposes handling plans for abnormal events that have occurred or may occur. Through the release of traffic information, it achieves the purposes of traffic control and guidance, provides effective management means for management departments, and provides good traffic information services for expressway users.

2. Composition

The traffic signal monitoring system of a road usually consists of the computer systems of monitoring sub-centers and monitoring nodes (if any), field devices, and transmission channels. According to the management system, computer systems can be divided into monitoring office computer systems, road monitoring sub-center computer systems, and provincial monitoring center computer systems. A computer system generally consists of monitoring servers, monitoring workstations, map boards, large-screen projectors, printers, scanners, automatic video traffic incident detectors, uninterruptible power supply devices, LAN switches, routers, and other components forming a local area network system. Field devices include: data acquisition devices such as vehicle detectors, meteorological detectors, and visibility detectors; and information release devices such as variable message signs, variable speed limit signs, lane indication signs, and signal lights. Transmission channels may use the dedicated expressway communication network, or use optical transceivers, Ethernet switches (routers), and optical fiber networking for transmission. Road monitoring sub-centers manage their respective road sections, and the provincial monitoring center monitors each road monitoring system. A road monitoring sub-center usually manages one road, or manages one or more (tunnel, bridge) monitoring offices, and itself has traffic data acquisition, data analysis and processing functions, traffic control functions, special event control functions, operation management functions, and so on. The provincial monitoring center manages several road monitoring sub-centers; it is positioned at a higher level of operation and coordinated management and has macro monitoring functions and centralized, unified coordinated control functions.