The objectives of this project are to design, test, and evaluate three ways of employing wireless communication, specifically to:

• Use probe vehicle data to characterize local freeway traffic speed and density, and then use that information to generate reference speed advisories back to individual drivers and vehicles to enact the speed control, to dissipate shock waves, and to improve throughput.
• Use vehicle-to-vehicle communication to generate reference speed and gap adjustment commands to cooperative adaptive cruise control systems, to enable them to follow more closely and safely, and also dissipate shock waves and increase throughput.
• Use vehicle-to-vehicle communication between heavy trucks to enable them to operate in close-formation automated platoons, increasing lane capacity, and reducing aerodynamic drag.

The fundamental technical approach follows the general iterative system paradigm of model-design-test-model. Mathematical and computer models will be used to predict system performance and interactions with the operating environment. These models will be the basis for making design tradeoffs and focusing on the preferred designs for testing. The preferred designs will be developed in prototype hardware and software (building on extensive legacy hardware and software from previous projects), and then tested under the most realistic conditions that are possible within schedule and budget constraints. The results of the tests will then be used to update the models, and the models will be used to predict the impacts of widespread implementation. Additional milestones have been defined for the intermediate completion of stages of system design, for the completion of test vehicle hardware and software installations, and for demonstrations that will be offered to the sponsors and stakeholders.

Goals

Advanced communication technologies can enable optimization of traffic management, improved traffic flow and capacity, and automated platooning (vehicles traveling very closely behind one another, also referred to as "road trains") of trucks.

• Exploratory Advanced Research

• FY 2002-2022 / Exploratory Advanced Research

• Vehicle to Infrastructure

This project has shown how connected vehicle systems, based on vehicle-vehicle and vehicle-infrastructure communication and coordination, can support the development of mobility-enhancing applications with the potential to transform the performance of the road transportation system. Three separate mobility-enhancing applications were developed, simulated, and tested, and their expected mobility benefits were estimated using simulations. Cooperative adaptive cruise control (CACC) was shown to have a high potential for user acceptance, and when applied at the gap settings chosen by representative drivers from the general public, it could double the capacity of a highway lane at full market penetration. Variable speed limits were shown to have the potential to reduce the adverse impacts of highway bottlenecks by increasing the traffic flow capacity of those bottlenecks if they can be implemented with smooth transitions in the speed limit settings. Automated truck platoon control was shown to be technically feasible using dedicated short range communications for vehicle-vehicle coordination, with the potential for significant fuel savings from aerodynamic drag reductions. 

The project team modeled, tested, and demonstrated prototype wireless communication systems to improve traffic flow by calculating and communicating variable speed limits (VSL) to drivers; achieve higher effective lane capacities using CACC; and reduce fuel consumption and increase truck-only lane capacity with automated platoons. Variable Speed Limits—In simulation and live tests on I–80, the researchers broadcast speeds calculated to prevent traffic flow breakdowns, with promising results. VSLs show significant potential to prevent traffic delays. CACC—Study results show that CACC could substantially increase highway capacity when it reaches moderate to high market penetration. Retrofitting non-CACC vehicles with inexpensive "here I am" radios could accelerate achievement of these capacity benefits. Automated truck platoon control—A wireless communications system successfully coordinated a platoon of three tractor-trailer trucks traveling at 85 km/h (53 mi/h) and in varied joining and splitting maneuvers. Fuel savings were estimated at 10 to 14 percent for the following trucks.