Evaluation of Transmit´s communication system

The System for Managing Incidents and Traffic (Transmit) is a traffic surveillance and incident detection system utilizing existing electronic toll traffic management technology of the E-ZPass system. Its communication system consists of the hardware installed at the roadside terminal (RST) readers to detect E-ZPass tag equipped vehicles (probes), telephone and radio links to transmit corresponding probe data and the computers and related peripherals at the operations information center (OIC) for real time processing of this data. The evaluation of the Transmit´s communication system was carried out to assess its transmission capability and reliability in terms of data transmission and detection rates. The transmission rates were determined based on the data collected at the RSTs and the corresponding data received at the OIC. The Transmit´s communication system exhibited excellent performance in terms of the transmission rates system wide, which was found to be near 100%. Only the radio link at Tappan Zee Bridge exhibited a lower transmission rate. A limited probe vehicle test was conducted to determine the detection rate at individual RSTs. The lower detection rates observed were site specific, rather than system wide. However, due to the high number of tag equipped vehicles that are expected in the future, the lower detection rates would not have any significant impacts on the determination of the traffic flow parameters (link travel time and space mean speed) as well as the incident detection capability.