What’s holding up truck platooning?
Nearly two-thirds of U.S. energy used for movement of freight is from the operation of Class 8 tractor trailers that carry it. So the opportunity for fuel savings of about 7%, as the big rigs cruise America’s highway system by “platooning,” close-following convoys of 2-4 vehicles, should have gained easy acceptance. What is holding up wide-area rollouts?
Enabling technology exists, an enhanced version of adaptive cruise control (already installed on some vehicles), permits trucks to “tailgate” safely, typically with a gap of just 45-50 ft (13.7-15.2 m) or 0.6 s at 55 mph (89 km/h). Testing shows fuel economy gains with gaps as small as 36 ft (11.0 m) and as large as 75 ft (22.9 m). The gaps create a slipstream effect, much like with “drafting” race cars.
Gap length is important for efficiency as well as safety. Wind tunnel tests by the Lawrence Livermore National Laboratory, a U.S. Department of Energy facility, showed if it’s too small, airflow in followers is reduced, forcing engagement of the cooling fan, and reducing energy saving. A too-small gap also may result in road film splashing up and restricting front end heat exchangers of following vehicles, which has a similar effect and would increase maintenance requirements.
Forward-looking sensors, heavy-duty brakes, and V2V (vehicle-to-vehicle) communication is what makes the close following convoy safe. Proponents have run successful on-highway demonstrations throughout the U.S. (Nevada, Texas, Utah, Michigan, California, Virginia) and Europe, at speeds ranging from 55 to 70 mph (). Although greater saving is with a following truck (up to 10%), the lead truck also benefits, typically using 5% less fuel.
However, all systems provide for the most common issue—a passenger car getting between two trucks—which might happen near an exit lane. When Peloton identifies this, it separates the trucks and after the car has left, a pushbutton system re-establishes the convoy.
Inasmuch as even DOE facilities have participated, why isn’t platooning in widespread use?
Although cost depends on how a truck already is equipped, and there’s no price list made public, Peloton Technology, developer of a leading system, maintains it is easily cost-effective, both from fuel-savings and driver-safety benefits. It can be retrofitted to any Class 8 vehicle with an owner that wants it.
Despite Federal participation, laws affecting U.S. close-following truck configurations are made by the states, and only a handful permit it now. Getting enabling laws passed in enough states to enhance value takes time, but some modest rollouts are likely to occur in the next few years.
There still must be a driver in each vehicle, but the automatic system controls acceleration and braking from the lead truck to the followers, and any driver can break from the convoy. However, in normal operation a driver is only responsible for steering. This is Automation Level 1, per definitions by SAE International, and the fuel economy test is per SAE J1321.
Peloton Technology is a Silicon Valley startup funded by Volvo Trucks N.A., Denso International America, Magna International, and several non-automotive investors. Peloton partners with Omnitracs, an international fleet management company that provides a cloud-based platform to organize platoons among subscribers, including different companies, and determine location and timing for efficient use of driver and truck operation times.
Other demonstrators have been Partners for Advanced Transportation Technology at University of California, Berkeley and the National Renewal Energy Laboratory, another DOE facility. A group of Dutch environmental agencies is promoting adoption of platooning in Europe.
In most cases, the V2V link uses DSRC (digital short-range communication), the 5.9-GHz band designated for short-range wireless vehicle communications, and a following driver can opt out at any time.
A normal platooning trip gives the following drivers easier workloads, but another delaying factor is how to monetize the technology. Nor has the question of interaction between drivers and trucks from different fleets, an advantage for the Omnitracs service. Fuel efficiency from platooning likely is limited to highway operation, not short distribution runs in metropolitan areas.