California Partners for Advanced Transportation Technology

In this project, we present the design, analysis and performance evaluation of the Integrated Roadway/Adaptive Cruise Control System (IRAC) proposed in Task Order (TO) 4242 and studied further in the continuation of TO4242 under TO5501. The IRAC system is a highway traffic control system which integrates ramp metering strategies and a speed control strategy by taking into account highway to vehicle communication, and adaptive cruise control (ACC) system technologies on board of the vehicles. The IRAC system closes the loop of an almost open loop highway traffic system by controlling both the ramps and the speed distribution along the highway lanes. The speed control and the ramp metering strategies are both extended and generalized versions of ALINEA and are designed based on the fundamental flow-density relationship. Available communication technologies such as Dedicated Short Range Communication (DSRC) systems are shown to be adequate to communicate to vehicles the desired speed limit commands generated by the IRAC system. The IRAC system is evaluated using the I-80 as a site for possible implementation. Real traffic data from the I-80 are used to validate a traffic flow simulation model developed using the software package VISSIM. The validated simulation model is then used to evaluate the IRAC system under different traffic scenarios involving mixed traffic ranging from 0% to 100% ACC vehicles, different traffic flow demands, recurrent and non recurrent disturbances.

The results demonstrate that the IRAC system could lead to a better managed traffic flow system where travel times are improved and the flows are smoother leading to potential improvements in safety and environment. While the magnitude of these improvements depends on the traffic situation and traffic disturbances, our results demonstrate consistent improvements under all scenarios considered. The report concludes by suggesting a stretch of the I-80 as a possible site for implementation due to the existence of traffic sensors as part of the Berkeley Highway Laboratory which minimizes changes to the existing infrastructure.