The California DOT implemented a three-truck Cooperative Adaptive Cruise Control system in mixed public traffic on California freeways.
Cooperative Adaptive Cruise Control (CACC) provides an intermediate step towards automated truck platooning. With CACC, only truck speed control will be automated using Vehicle-to-Vehicle communication. The driver of the truck will be responsible for steering the vehicle, lane keeping, and monitoring roadway traffic conditions.
A CACC system was implemented on three truck tractors and tested under a variety of conditions to assess its potential impacts. The control system was tested to demonstrate its ability to maintain accurate spacing between trucks and to respond safely to maneuvers by drivers of other vehicles. The energy saving potential of the close formation of the trucks was tested through test-track experiments. Truck driver responses to the CACC system were assessed through opinions of the truck drivers on the system and about gap settings they preferred to use while driving in mixed public traffic on California freeways.
The larger-scale impacts of truck CACC on traffic flow and energy consumption were done in computer simulation. It showed the potential to relieve traffic bottlenecks and improve the speed and smoothness of traffic for all vehicles on the freeway as well as reducing fuel use and emissions.
When the heavy trucks are driven using CACC at the tested time gaps between 0.6 seconds and 1.5 seconds, a three-truck platoon pulling conventional well loaded dry goods van trailers can save a total of between about 6 percent and 5 percent respectively of its fuel consumption when cruising at 65 mi/h. The first truck does not experience any significant saving, while the second truck saves between 7 percent and 6 percent and the third truck saves between 11 percent and 9 percent.
The use of truck CACC can produce noticeable congestion reductions when used on a moderately congested urban freeway corridor with a substantial percentage of heavy truck traffic. The relief of traffic bottlenecks saves significant time and fuel for the trucks, with modest congestion relief effects for the cars that share the freeway with the trucks.