Supplementary Benefits from Partial Vehicle Automation in an Ecoapproach and Departure Application at Signalized Intersections

One of the objectives of the U.S. Department of Transportation's connected vehicle (CV) research program is to develop innovative applications that take advantage of communications between vehicles and roadside infrastructure as well as between the vehicles themselves to improve safety, mobility, and the environmental performance of multimodal transportation systems. Many of the energy- and environment-focused CV applications involve the prescription of optimal speed profiles for vehicles that travel within the transportation network. These recommended speed profiles can then be provided to the drivers through human machine interfaces (HMIs). However, the drivers may not be able to follow the recommended speed profiles closely. In that case, the effectiveness of the applications might be degraded. These HMIs may even be distracting and detrimental to safety. Partial vehicle automation can be used to follow a recommended speed profile and play an important role to ensure that the benefits of these CV applications are realized fully. This paper presents an evaluation of the supplementary benefits from partial vehicle automation in CV applications with the use of an ecoapproach and departure application at signalized intersections in a case study. This application provides recommended speeds for vehicles as they approach and travel through a signalized intersection so that they pass through the intersection on green or decelerate to a stop in the most ecofriendly manner. The evaluation was based on real-world HMI manual driving data and in simulated partial automation data. The results showed different levels of supplementary benefits, which depended on the ability of the drivers to follow the recommended speeds, compared with the actual target speed profiles that would have been achieved through partial vehicle automation.