Impacts of Road Trains on the Geometric Design of Highways

Abstract

Traffic congestion and greenhouse gas emissions from vehicles have alarmingly increased over the past decades as a result from people's daily commute. Building newer and larger roads to improve traffic flow and decrease emissions is no longer an option. Transportation needs to embrace higher levels of sustainability and efficiency in order to solve one of the greatest 21st century's problems. Not surprisingly, engineers and researchers develop nowadays many valuable and green engineering ideas for transportation changes. One such idea creates automated or semi-automated platoons or road trains of vehicles on highways in order to achieve multiple benefits including considerable reduction in emissions through enhanced aerodynamic characteristics, relief of traffic congestion through better road space utilization, and improvement of safety and driver comfort through use of fail-safe mechanisms and shock wave reductions. Still, the interactions between the human factors, or truly the lack thereof, and the new technologies may directly impact on the traditional guidelines for the geometric design of highways. Required new technology is mostly built into passenger cars and further targets their operation, which results in a lack of necessity to continue to extend the existing roadway infrastructure. This thesis presents these potential changes in design guidelines. The investigation of a continuum of transitory to end state scenarios concluded that overall road train modes of highway operation displayed a strong potential to significantly reduce the minimum lengths requirements on vertical and horizontal curves alike. Existing freeway designs are thus more than satisfactory for the deployment of these operational modes.