Assessing the potential impacts of connected vehicle systems on Driver’s situation awareness and driving performance

Vehicles equipped with connected vehicle technologies are able to communicate with each other and with infrastructures. Compared to Advanced Driving Assistance Systems (ADAS) using camera systems and sensor technologies, the Connected Vehicle Systems (CVS) leverage the wireless communication networks to detect hazards with a greater range, alert drivers of hazards much earlier, and therefore enhance driving safety. However, drivers’ reliance on the CVS to detect critical situations could negatively affect them maintaining situation awareness (SA) in noncritical situations when no warning is issued by the CVS. The present study conducted a driving simulator experiment with 40 participants to investigate the effect of connected vehicle systems on driver SA in normal, noncritical driving scenarios after they were exposed to the CVS with different designs of collision warning lead time (3 s, 6 s, and no warnings). After drivers experienced the CVS-supported warnings with the assigned design of lead time in critical situations, driver SA was measured in normal driving conditions using the freeze probe technique. Results revealed that drivers who experienced the CVS with early warnings (6 s) showed lower SA for normal driving events compared to those who experienced the CVS with late warnings (3 s) or no warnings. Although early warnings of CVS brought more safety benefits to drivers in critical situations, the degraded driver SA due to drivers’ reliance on such warning systems could endanger drivers when a system failure occurred. These findings highlight the importance of balancing the effects of warning lead time on driver SA and driving performance in designing connected vehicle systems.     

Behavior model and guidance strategies of the crossing behavior at unsignalized intersections in the connected vehicle environment

The connected vehicle environment is considered to be a disruptive technology that reconstructs the way people travel and road transport, and more importantly, ensures traffic safety. This study aims on investigating drivers’ interactive behavior at an unsignalized intersection in the connected vehicle environment. Specifically, a simplified iterative behavior model was established to predict the potential conflicting vehicles’ behavior. Furthermore, based on principles of safety, efficiency, and comfort, the guidance strategies were proposed to help the subject vehicles cross intersections. A multi-user driving simulator experiment was carried out and 48 participants were divided into 24 pairs to complete the test. The simplified iterative behavior model was constructed based on the dynamic interaction of each participant pair as they approached the intersection from straight-crossing directions. The comparison results showed the behavior model was an effective microscopic simulation tool for vehicles at unsignalized intersections with high accuracy and good applicability. Then, the guidance strategies under different compliance rates (baseline, 50 % compliance, 100% compliance) were evaluated based on three indexes i.e. standard deviation of speed (SDS), duration of crossing the intersection (DCI), and time exposed post-encroachment-time (TEP). The numerical simulation results showed that the guidance strategies could effectively improve the safety and efficiency of drivers crossing the intersection under both 50% and 100% compliance rates. Besides, with the increase of compliance rate, the comfort level also increased evidently. This study can provide theoretical and algorithmic references for microscopic simulation and guidance strategy at unsignalized intersections in the connected vehicle environment.     

Evaluating the influence of approaching vehicles on pedestrian’s visual patterns and crossing behaviors at an uncontrolled crosswalk

The visual behaviors and movement characteristics of pedestrians are related to their surrounding potential safety hazards, such as approaching vehicles. This study primarily aimed to investigate the visual patterns and walking behaviors of pedestrians interacting with approaching vehicles. Field experiments were conducted at two uncontrolled crosswalks located at the Cuihua and Yanta roads in Xi’an, China. The visual performance of pedestrians was assessed using the eye tracking system from SensoMotoric Instruments (SMI). Moreover, motion trajectories of the pedestrians and approaching vehicles were obtained using an unmanned aerial vehicle. Subsequently, the visual attributes and movement trajectories of pedestrians and motion trajectories of approaching vehicles were statistically analyzed. The results showed that approaching vehicles distracted the fixation of crossing pedestrians significantly, and occupied 29.5% of the total duration of fixation; that is, pedestrians always directed more fixation points to the approaching vehicles compared to other stimuli. As a vehicle approached, pedestrians’ fixation shifted from other areas of interest to the vehicle. Moreover, an increase in the velocity of the vehicle and a closer distance between pedestrian and the vehicle resulted in an increase in the pedestrians’ duration of fixation on the approaching vehicle, and they implemented more saccades. Furthermore, approaching vehicle’s velocity and distance between pedestrian and approaching vehicle are not significantly associated with pedestrian’s movement attributes. These findings provide insights into the crossing behavior of pedestrians during pedestrian-vehicle interactions, which could assist future researchers and policy makers.     

Driver brake vs. steer response to sudden forward collision scenario in manual and automated driving modes

In autonomous vehicle operation, situations may arise when the driver is required to re-engage in manual control of the vehicle. Whether the control handoff from vehicle to human is done in a structured or unstructured manner, the process may be affected by the driver’s state, i.e. distracted or not. The study reported here was designed to measure a non-distracted driver’s response to a sudden forward collision (FC) event, in which the driver would assume manual control of the autonomous vehicle. Three driving scenarios were investigated: autonomous vehicle driven with full collision avoidance support, autonomous vehicle driven without collision avoidance support, and vehicle driven in manual mode.Forty-eight volunteers participated in a simulator study conducted in VIRTTEX. It was found that, at handoff, (1) drivers in manual mode tended to use evasive steering, rather than braking, compared to drivers in both the autonomous modes, (2) between subjects variations in speed were higher for the automation with collision support condition than for the other two scenarios, (3) for both autonomous driving scenarios, drivers reaction times were longer than for manual driving. In some cases the driver response was so late and the distance remaining so reduced that crash avoidance might be unfeasible. At a minimum, results of this study suggest that drivers may benefit from appropriate driver assistance technologies when a crash imminent situation is suddenly encountered.     

First-time experience of critical range situations in BEV use and the positive effect of coping information

A frequently discussed phenomenon in the context of limited range as a usage barrier for battery electric vehicles (BEVs) is range anxiety (i.e., range stress). The objective of the present research was (1) to examine if the effect of first-time experience of a critical range situation on inexperienced BEV drivers’ range experience (e.g., range stress) is rather positive or negative, (2) to examine if providing minimal coping information can enhance this effect and (3) if a positive adaptation effect can be found under different criticality levels regarding the available range. A field experiment was conducted, in which 74 participants drove a BEV in a critical range situation (i.e., experience of a small range safety buffer) on an unaccompanied 94 km round trip. Results indicate that the first-time experience of a critical range situation has a moderate positive effect on range stress (i.e., reduced range stress after the trip compared to range stress before the trip), that coping information can partly enhance range experience and that these positive effects can be found under both examined criticality levels (critical vs. highly critical range situation). The results can be useful to inform strategies aimed at reducing the experience of range stress in the early period of BEV usage.     

Parameter selection based on fuzzy logic to improve UAV path-following algorithms

In order to steer an Unmanned Aerial Vehicle (UAV) and make it follow a desired trajectory, a high level controller is needed. Depending on the control algorithm, one or more parameters have to be tuned, having their values high impact on the performance. In most of the works, these parameters are taken as constant. In this paper, we apply fuzzy logic to select the parameters of the control law and compare this approach with the tuning by constant parameters and with another adjusting method based on the kinematic analysis of the equations of the UAV. After many simulations of the quadrotor following randomly generated paths, we have proved that the fuzzy tuning law is not only a good and feasible solution, but also more general as it can be applied to any trajectory.     

Reduction of police vehicle accidents through mechaniically aided supervision

Tachograph recorders were installed in 224 vehicles of a metropolitan police department to monitor vehicle operation in an attempt to reduce the rate of accidents. Police sergeants reviewed each tachograph chart and provided feedback to officers regarding their driving performance. Reliability checks and additional feedback procedures were implemented so that upper level supervisors monitored and controlled the performance of field sergeants. The tachograph intervention and components of the feedback system nearly eliminated personal injury accidents and sharply reduced accidents caused by officer negligence. A cost-benefit analysis revealed that the savings in vehicle repair and injury claims outweighed the equipment and operating costs.     

Evaluation of two methods of prompting drivers to use specific exits on conflicts between vehicles at the critical exit

The Florida Department of Transportation used a series of changeable-message signs that functioned as freeway guide signs to divert traffic to Universal Theme Park via one of two eastbound exits based on traffic congestion at the first of the two exits. An examination of crashes along the entire route indicated a statistically significant increase in crashes at the first eastbound exit following the actuation of the system. Furthermore, all of the crashes occurred in close proximity to the exit gore (the crosshatched area at exits that drivers are not supposed to enter or traverse) at the first exit. In Experiment 1, behavioral data were collected using an alternating treatments design. These data revealed that reassigning the exit signs was effective in producing a change in the percentage of drivers using each of the two exits. These data also showed that the reassignment of the theme park exit was associated with an increase in the percentage of motor vehicle conflicts that consisted of vehicles cutting across the exit gore. An analysis revealed that the method used for switching the designated or active theme park exit on the series of changeable-message signs led to the presentation of conflicting messages to some motorists, thus resulting in erratic driving behavior (cutting across the exit gore). In Experiment 2, the treatment evaluated the use of a phased method of switching the designated theme park exit to eliminate the delivery of conflicting messages. The new method for switching the designated theme park exit was not associated with an increase in motorists cutting across the exit gore.     

Suicide by crashing into a heavy vehicle: A one-year follow-up study of professional drivers

Train and heavy vehicle drivers can experience a traumatic event caused by people attempting suicide by crashing into their vehicles or jumping in front of them. While there are a number of studies on train drivers showing the negative consequences these events can have on their well-being, there are no studies on heavy vehicle drivers involved in these types of crashes. In the current study, we surveyed Finnish heavy vehicle drivers (N = 15) involved in a suicide crash in the year 2017 regarding their experiences and coping approximately one month (T1) and one year (T2) after the crash. Ten of these drivers reported one or various combinations of measurable consequences such as minor physical injuries, shorter or longer sickness absences, significant posttraumatic stress symptoms (measured using the Impact of Events Scale-Revised) and requiring psychological help. Posttraumatic stress symptoms decreased over time; however, three out of the four drivers who had a high IES-R score at T1 were still around the IES-R cut-off score at T2. This research raises questions whether and what kind of support heavy vehicle drivers who have been involved in a suicide crash should be given.     

Methodological considerations for longitudinal investigations of young drivers

IntroductionMotor vehicle crashes (MVCs) are the leading cause of mortality among teenagers. Teen driving research has a longstanding history; however, much of this work is cross-sectional. The Eunice Kennedy Shriver National Institute for Child Health and Human Development funded a study, REACT (Roadway Experiences and Attentional Change in Teens) which combined factorial and longitudinal designs to investigate the independent and joint effects of age and driving experience on driving attention over time among young drivers.MethodLongitudinal methods offer important contributions to teen driving research by enabling characterization of driving trajectories. This paper describes methodological considerations for longitudinal studies of teen drivers. Such considerations are organized into overarching themes, including population, recruitment, enrollment, and retention, throughout this paper. These considerations were compiled as a combination of our own experiences in REACT and previous literature. We elaborate on these considerations below to illustrate the value of each consideration.ResultsIssues encountered are discussed and strategies for dealing with various issues are described. Transportation barriers, scheduling difficulties, and skipped study milestones were among the most frequent challenges; we outline these and other issues encountered in REACT and corresponding considerations for such issues in Table 2. Sharing these experiences should aid future longitudinal investigations of young drivers, which are critically needed to reduce teen MVCs.ConclusionsStudies similar to REACT are considerable undertakings due to the comprehensive nature of longitudinal design. Such investigations must maintain a delicate balance between appropriate amounts of rigor and flexibility in the development of thoroughly defined research questions and theoretically driven frameworks. Key considerations that have contributed to the success of REACT are outlined, challenges encountered throughout data collection are documented, and recommendations based on choices made and lessons learned to inform future longitudinal investigations on young drivers are provided.