Tests of Traffic Sensors and Telemetry Services

This paper presents the results from field deployments and tests of eight portable and semi-portable detector systems. These tests are the culmination of four years of research conducted to determine suitable, primary non-intrusive, traffic detector systems for use by the Hawaii DOT for its traffic monitoring program. Three types of sensor installation were made, underground or sub-surface, on-ground and above ground, side-fired. All three above ground, side-fired, unintrusive sensors (SAS-1, SmartSensor and RTMS) provided reliable and reasonably accurate volume and speed data when properly installed and calibrated. Among the four on-ground sensors capable of providing vehicle classification data (in 13 classes), the Roadtrax BL piezoelectric sensor was the only one that was capable of providing adequate and reliable data. The systems tests included evaluations of telemetry and other services for data retrieval and remote diagnostics. TrafInfo’s Trafmate satellite modem and digital pager, and TrafficWorks’ near-real time data retrieval via cellular sub-carrier and integrated archival system performed satisfactorily and were far superior to classical Hayes modems. The research was extended to evaluate the potential for modifying signalized intersections for traffic data given the expanded functionality of the sensors, systems and services purchased. The remote collection of volume data without interfering operations at a busy 5-phase signalized intersection was possible from an intersection’s 332 traffic cabinet with a loop actuated Type 170 corridor using Canoga loop boards, and adding a TransHub and TrafInfo digital pager. Other tests showed the potential of remote collection of a near-real time freeway data from legacy equipment by adding Canoga detector cards. CDMA modems and service integration with Internet data retrieval by TrafficWorks.