Selected Mobility Applications for VII

Developing and Evaluating Selected Mobility Applications for Vehicle-Infrastructure Integration (VII) – Steven E. Shladover

This project describes the development and evaluation of three cooperative mobility applications. It was sponsored by the FHWA Exploratory Advanced Research Program (DTFH61-07-H-00038) and Caltrans (TO 6224). These applications employ DSRC wireless communications, between vehicles and between vehicles and the roadway infrastructure, to improve traffic flow on limited-access highways. The first application combined ramp metering with variable speed limits to enhance traffic flow and avoid traffic breakdowns at bottleneck locations. The second application used vehicle-to-vehicle communication (to improve the performance of adaptive cruise control systems) along with vehicle-to-roadside communication to provide adjustments to their set speed and gap settings (to improve lane capacity and mitigate congestion) and the third application used vehicle-to-vehicle communications to implement close-formation truck platooning.


Field testing of Cooperative Adaptive Cruise Control (CACC) on light duty vehicles produced highly favorable results. These included excellent vehicle-following performance and a high level of user acceptance by the test subjects, from the general public, who drove the vehicles.  These results showed that subjects, driving CACC equipped vehicles, were comfortable with much smaller car-following gaps (about half) than standard gaps employed by adaptive cruise control - on the same test vehicles.  Traffic simulations showed that the reduced following distance that CACC enables, provided the potential for an increase in lane capacity (up to 4000 vehicles per hour per lane) if all vehicles were equipped with CACC and the drivers chose the same car following settings (gaps).  This work led Nissan to support follow-on research to improve the CACC syste performance.

Automated truck platoon experiments were implemented, based on CACC integrated into three Class-8 truck tractors. These experiments demonstrated the technical feasibility of a three-truck coordinated platoon, driving at gaps as short as 4 m – under a variety of maneuvers (including speed and grade changes and platoon joining and splitting).  Fuel consumption measurements showed the first truck saving about 5% energy and the following trucks saving 10% to 15% energy. The favorable results of these tests led to follow-on projects to develop and test the next generation of truck platooning systems on a new set of trucks, in collaboration with FHWA, Caltrans, Volvo Group and the U.S. Department of Energy.

The implementation of variable speed limits (VSL) was studied through simulation and field testing. The simulations showed that VSL has potential to increase the effective capacity of a highway at a recurrent bottleneck. VSLs reduce the speed of the traffic approaching the bottleneck, from upstream, and avoid traffic flow breakdown.  The VSL speed advisories were communicated to test vehicles driving on local freeways, where they were displayed to drivers. This demonstrated that real time traffic management can be done with I2V data communication.  These results, the simulation in combination with the data communication demonstration, were sufficiently promising to lead Caltrans to sponsor a follow-on project and for the FHWA STOL Laboratory to test variable speed limits, based on the method developed in this project, in the Washington DC region.

Reports and Working Papers:

Development and Assessment of Selected Mobility Applications for VII: Principal Findings, UCB-ITS-PRR-2011-14, July 2011, Contract DTFH61-07-H-00038

Automated Truck Platoon Control, UCB-ITS-PRR-2011-13, June 2011, Contract DTFH61-07-H-00038

Freeway Traffic Control Using Variable Speed Limits, UCB-ITS-PRR-2011-11, September 2011, Contract DTFH61-07-H-00038

Development and Evaluation of Selected Mobility Applications for VII, UCB-ITS-PRR-2011-09, July 2011, Contract 65A0351

Development and Evaluation of Selected Mobility Applications for VII, UCB-ITS-PRR-2011-08, July 2011, Contract 65A0351

Development and Evaluation of Selected Mobility Applications for VII, UCB-ITS-PRR-2010-25, April 2010, Task Order 6224

Development and Evaluation of Selected Mobility Applications for VII: Concept of Operations, UCB-ITS-PWP-2009-3, March 2009