Commercial Truck Platooning to Reduce Energy Consumption

Introduction

Fig. 1: A Scania Heavy Truck. (Source: Wikimedia Commons)

Commercial freight trucking accounts for a significant percentage of vehicle traffic in the United States. These trucks consume much more fuel per mile driven than most passenger vehicles, on average reporting fuel efficiencies of just 5.9 miles per gallon. [1] The significant operating cost of fuel gives freight companies a large incentive to increase fuel efficiency.

In addition to consuming a large amount of fuel, commercial trucking is responsible for a significant amount of carbon emissions. One study estimated that the amount of carbon-dioxide emissions from trucking in Japan accounted for more than 6% of the emissions for the entire country. [2]

One proposed method to increase efficiency, vehicle platooning, has gained increasing interest over the past decade. This paper will present an overview of vehicle platooning technologies and their potential to reduce trucking fuel consumption and carbon emissions.

Background

Several projects over the past 20 years have researched the problem of platooning vehicles. Though a large number of these projects exist, this paper will introduce three as a background to the platooning field. At the University of California, the PATH program sought to increase highway capacity by platooning passenger and commercial vehicles. [3] The PATH program focuses on longitudinal control, using automated systems to control the speed of each truck and its distance to the truck preceding it. The program assumes there would be a dedicated commercial truck lane for the platooning vehicle so that they would not have to contend with erratic passenger vehicles. [2]

Scania, the Swedish commercial truck manufacturer, is also researching an automated longitudinal control system for heavy truck platoons. A Scania heavy truck is shown in Fig. 1. In addition to researching the control system for individual trucks, Scania, partnered with KTH (The Royal Institute of Technology) is researching how to control platoons as a whole on the highway. [4]

KONVOI is a platooning project carried out by RWTH Aachen University in Germany. This projects motivation was a combination of the previous two: to increase traffic capacity on public roadways, and to decrease fuel consumption of heavy trucks. [2] Rather than acting autonomously, the KONVOI project looks longitudinal and lateral tracking assistance to the driver, following a manually driven preceding truck. [5] Unlike the PATH project, KONVOI is designed to work with existing highway infrastructure. [2]

Effects on Fuel Consumption and Emissions

The increase in fuel efficiency of heavy trucks while platooning can be largely attributed to decreased air drag on each truck in the platoon. [6] To decrease air drag, following vehicles must decrease the following difference between trucks in the platoon. Following distances between 25 m and 5 m are common. [2] At these short distances, human reaction is not fast enough to avoid potential collisions at highway speeds, necessitating the use of automated control systems.

While estimates of fuel efficiency increase vary over projects, significant improvements are normally observed in platooning tests. The SATRE project reported fuel savings were between 2% and 8% for the lead vehicle and between 8% and 12% for the following vehicle. [7]

As discussed in the introduction, platooning can improve not only fuel efficiency, but also decrease harmful emissions. The Energy ITS project estimated that if 40% of the trucks on the highway employed platooning technology, the total carbon-dioxide emissions from highway traffic would be reduced by 2.1%. [2]

Conclusion

Heavy duty truck platooning is a promising technology which promises improvements in fuel consumption, emissions, and traffic congestion. Reducing air drag by reducing following distance of trailing vehicles, each truck in a platoon uses less fuel per mile traveled. Many different methods are being explored to implement platooning technology, with varying levels of complexity and required infrastructure changes.

© John Talbot. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] M. Sivak and O. Tsimhoni, "Fuel Efficiency of Vehicles on US Roads: 1923-2006," Energy Policy 37, 3168 (2009).

[2] S. Tsugawa, S. Jeschke and S. Shladover, "A Review of Truck Platooning Projects for Energy Savings," IEEE Trans. Intell. Veh. 1, 68 (2016).

[3] X.-Y. Lu and S. E. Shladover, "Automated Truck Platoon Control and Field Test," in Road Vehicle Automation, ed. by G. Meyer and S. Beiker (Springer, 2014), pp. 247-261.

[4] A. Alam et al., "Guaranteeing Safety for Heavy Duty Vehicle Platooning: Safe Set Computations and Experimental Evaluations," Control Eng. Pract. 24, 33 (2014).

[5] M. Alfraheed et al, "Longitudinal and Lateral Control in Automated Highway Systems: Their Past, Present and Future," in Intelligent Robotics and Applications, ed. by S. Jeschke, H. Liu and D. Schilberg (Springer, 2012), pp. 589-598.

[6] J. Nash, "Getting Their Trucks in a Row, Europeans Revisit the Convoy," New York Times, 29 Sep 13.

[7] M. Poorsartep and T. Stephens, "Truck Automation Opportunities," in Road Vehicle Automation 2, ed. by G. Meyer and S. Beiker (Springer, 2015). pp. 173-185.