# Efficient Position Change Algorithms for Prolonging Driving Range of a Truck Platoon
## 2 Literature Review  
Several research institutions and transportation manufacturers have eagerly studied and developed truck platooning technologies for decades, expecting a fully automated vehicle in the current timeline and bringing human beings a brighter future in the freight industry and transportation system. According to the levels of driving automation by SAE International [10], Level 5 or full automated refers to full driving automation, where vehicles automatically pilot themselves in all driving environments with no human driver required. Still, truck platooning realizes only SAE level 2 automated driving, where trucks are allowed to control both steering and acceleration/deceleration capabilities, yet the driver is needed and makes it fall short of self-driving automation. An effort aims to address challenges to accomplish platooning systems for higher automation levels, as well as ascertaining solutions to enhance fuel efficiency. Several studies have proved the benefits of reduced aerodynamic phenomena. However, vehicle configurations and other subject influencing factors are needed to be studied to achieve optimal fuel savings in the platoon. For example, the following questions should be addressed. * What are the influencing factors on fuel consumption reduction in the truck platooning system? * What are optimal configurations of trucks to get the highest fuel savings? * Does vehicle position in the platoon affect fuel consumption for each truck? If yes, how does it remarkably influence the fuel consumption reduction in each position? Many papers have been studied to answer the above questions. In early 2000, [PERSON] et al. [4] conducted two-truck platooning experiments with heavy-duty ACTROS semi-trailer trucks. The lead truck is driven manually, and the trailing truck is operated automatically with a driver assistance system. Two measurement tests were carried out with two constant velocities of 80 km/h and 60 km/h and inter-vehicle distances from 5 m up to 16 m. The trailing truck experienced a remarkable fuel consumption reduction of 21% at 80 km/h velocity with 10 m longitudinal spacing, and the leading truck experienced a 7% reduction in the corresponding configurations. The demonstration results further show that both velocity and inter-vehicle distance significantly impact the fuel consumption reduction where the decreasing gap space makes reduction benefits increase, whereas decreasing speed makes the opposite outcomes. It should also be noted that the leading truck can also have fuel reduction in platooning compared to that case of driving alone. A platoon of three tractor-trailer truck experiment was conducted under automated longitudinal platoon control by [PERSON] et al. [5] in 2011. Besides the environmental conditions, they considerably investigate the effects of the position within the platoon and the inter-vehicle spacing. With three heavy trucks at 85 km/h speed and a gap spacing of 6 m, the third truck saves the most fuel among the three, and the second still achieves more fuel-saving than the first truck. To be specific, the leading truck achieves 4.3% of reduction in fuel consumption, and about 10% and 14% fuel savings are achieved for the second and the third truck, respectively. The aerodynamic simulation in a two-truck platooning by [PERSON] et al. [6] has been carried out to select the most appropriate gaps between the platoon in 2013. This work consists of a series of CFD (Computational Fluid Dynamics) simulations from 3 m to 15 m gap spacing configurations, considering steady environmental conditions at 90 km/h velocity. The results show that trucks in the platoon remarkably achieve fuel-saving approximately from 7% to 15% at 8 m inter-vehicle distance, and about only 2% to 11% fuel saving at 15 m. This work also confirms that the fuel consumption can be reduced with the shortened gap spacing. [PERSON] et al. (2014) evaluated a two Class 8 tractor-trailer platoon on fuel consumption in 2014.