Accident Analysis and Prevention 148 (2020) 105793 Available online 2 October 2020 0001-4575/© 2020 Elsevier Ltd. All rights reserved. Evaluation of augmented reality cues to improve the safety of left-turn maneuvers in a connected environment: A driving simulator study Alessandro Calvi *, Fabrizio D’Amico , Chiara Ferrante , Luca Bianchini Ciampoli Department of Engineering, Roma Tre University, Via Vito Volterra 62, 00146, Rome, Italy A R T I C L E INFO Keywords: Left-Turn maneuvers Augmented reality Driving simulator Virtual warnings Road safety Connected vehicle ABSTRACT Left-turns are some of the most dangerous maneuvers drivers face as they involve a complex decision-making process. Indeed, drivers must wait for an adequate gap in oncoming traffc to safely complete a left-turn ma- neuver. In this context, incorrectly assessed gaps can lead to severe crashes and severe traffc delays at in- tersections. This study tests the potential of Augmented Reality (AR) technology, built into connected vehicle technology, to improve the safety of left-turn maneuvers of connected vehicles by adding visual virtual infor- mation to the driver. To achieve this goal, a driving simulator study was carried out. The effectiveness of the system was tested, and the ability of young drivers to detect adequate gaps between vehicles in the opposite lane (with right of way) to safely turn left was assessed with and without AR warnings at a two-way stop-controlled intersection under a connected vehicles environment. In the scenario projected on the simulation screen, three different virtual warnings were displayed and tested: a green/red traffc light, which informs the driver of the availability of an appropriate gap between opposing vehicles; a traffc light with a timer showing the number of seconds available to safely perform the left-turn maneuver; a traffc light with an additionally activated audio warning system. Signifcant positive effects of AR warnings on driving performance and traffc safety were observed: the number of safe left-turns increased and the delays at the intersection decreased. In addition, AR signaling improved driving behavior both during the waiting time, with many more drivers waiting for the gap in front of the stop line to avoid disrupting oncoming traffc, and turning movement, reducing the average time it took to complete the left-turn maneuver. This study confrmed the great potential of AR and connected vehicle technologies to improve general safety conditions on the road network, especially under risky situations and diffcult maneuvers. 1. Introduction Improving road safety is certainly one of the greatest challenges in the world. The number of road accidents, injuries and deaths is dramatic everywhere, and the social costs associated with road accidents are seen as the greatest challenge facing developed and developing countries. According to the Global Status Report on Road Safety (World Health Organization, 2018), the price of mobility is too high; worldwide, 1.35 million people die on the roads every year. The data are worrying, especially given the existence of several effective safety measures. Drastic actions are needed to put these measures in place to save lives, especially at intersections. In 2016, over 25,700 people died in road accidents across the EU, of which 5000 were killed in road accidents at intersections (European Commission, 2018). The Federal Highway Administration reports that approximately 15,000 vehicles are involved in accidents at intersections in the United States every year. They make up around 30% of all vehicles involved in road accidents (National Highway Traffc Safety Adminis- tration (NHTSA), 2017, Table 32). In addition, a previous study (Na- tional Highway Traffc Safety Administration (NHTSA), 2010) reports that about 40% of accidents in the US in 2008 were intersection-related accidents. However, the safety problems at intersections are a global problem with similar consequences worldwide. According to Elvik and Vaa (2004), around 40% of all accidents in Norway occurred at intersections. In Singapore, crash data collected from 1992 to 2002 showed that more than a third of accidents occurred at intersections (Tay and Rifaat, 2007). Similarly, more than 30% of road deaths and 40% of serious road accidents in Canada have been reported at intersections (Barua et al., 2010). With regard to Australia, intersection accidents accounted for * Corresponding author. E-mail address: alessandro.calvi@uniroma3.it (A. Calvi). Contents lists available at ScienceDirect Accident Analysis and Prevention journal homepage: www.elsevier.com/locate/aap https://doi.org/10.1016/j.aap.2020.105793 Received 12 February 2020; Received in revised form 14 September 2020; Accepted 16 September 2020