Licentiatavhandling Stockholm : Kungliga tekniska högskolan. Institutionen för transportvetenskap, 2016

Coupled with the growth of world economy, the demand for freight transport has escalated and will continue to do so. As the traffic intensity increases, the pressure on infrastructure, energy usage and environment becomes higher than ever. Meanwhile, the number of traffic accidents is also increasing year by year as a result. Heavy-duty vehicle (HDV) platooning makes a group of HDVs driving closely after each other. It is one potential solution to improve transport efficiency, traffic safety and fuel economy. Even though there have been extensive studies on the platooning system and corresponding fuel saving, some of the research areas, such as coordination strategies of platooning, platoon operations and the impacts of HDV platooning on traffic flow are still left open. Under a futuristic scenario where a large number of HDVs will be operating in one or several platoons on highway, how to group HDVs into a platoon and how to select spacing policies for HDV platooning are essential for automobile manufacturers, fleet operators and transport planners. Therefore, the formation strategies and operations of HDV platoons, as well as the impacts of HDV platooning on traffic flow have to be carefully investigated. This thesis presents contributions to the modeling of HDV platooning and simulation of HDV platoon operations. The focus lies mainly on analytical formulation of speed-density relation of mixed traffic flow and development of simulation framework for study of HDV platooning. On the one hand, a three-regime speed-density relation is proposed to describe the mixed traffic flow consisting of HDVs and passenger cars. The proposed speed-density relation incorporates percentage of HDVs, traffic density and spacing policy of HDV platoons as input variables and delivers aggregate highway velocity as output. By comparing the traffic throughput of no HDV platooning scenario, grouping HDVs into platoon using constant vehicle spacing policy or constant time gap policy results in significant improvement in highway capacity. On the other hand, a simulation framework is developed for implementation of different HDV platoon operations. The platoon formation of two HDVs and disaggregation of a five-HDV platoon at off-ramp are simulated on a two-lane highway. The simulation outcomes show that HDV platoon formation is more favorable in light and medium traffic; disaggregation of a long HDV platoon at off-ramp improves the average speed of passenger vehicles considerably at high traffic flow rate.