Investigating driving instructors: The mediating roles of driving skills in the relationship between organizational safety strategies and driver behaviours

The aim of the present study is to investigate the mediating roles of driving skills in relationship between organizational safety strategies and driver behaviours among driving instructors. Driving skills consist of perceptual-motor skills and safety skills. Driver behaviours are investigated under four factors: violations, errors, lapses, and positive driver behaviours. Participants were 132 driving instructors (108 male and 24 female). In order to measure organizational safety strategies, Organizational Safety Strategies Scale (OSSS) was developed for driving schools. Results of the principal component analyses yielded one-factor solution for OSSS. In order to test the indirect effects of organizational safety strategies on driver behaviours through driving skills, multiple mediation analyses were conducted by entering age and annual mileage as the control variables. As organizational safety strategies were stronger, driving instructors had higher levels of perceptual-motor skills, which resulted in higher violations. On the other hand, as organizational safety strategies were stronger, driving instructors had higher levels of safety skills, which resulted in less violations and lapses. It can be inferred that; organizational stronger safety strategies might have negative influences on road safety through higher perceptual-motor skills; whereas there can be positive influences on road safety through higher safety skills. In addition, both skills are related to organizational safety strategies. Hence, driving schools should consider the asymmetric relationship between perceptual-motor skills and safety skills while improving their safety strategies to decrease violations and lapses. Organizations might also develop interventions to balance the stated skills to increase road safety.     

The safety performance of connected vehicles on slippery horizontal curves through enhancing truck drivers’ situational awareness: A driving simulator experiment

Although drivers can adequately adjust their operating speed according to the road curvature, they show a lack of recognition regarding the pavement friction conditions. In this regard, inappropriate speed selection on Horizontal Curves (HCs) with reduced surface friction can lead to a remarkable rate of run-off-road, sideswipe, head-on, and rollover crashes, especially on rural highways. Aligned with the Connected Vehicle (CV) Pilot Program on Interstate-80 in Wyoming, this study scrutinizes how CV advisory/warning messages can enhance traffic safety on slippery HCs. To this aim, a roadway consists of two HCs with regular and slippery pavement conditions was designed in a high-fidelity driving simulator experiment. A total of 24 professional truck drivers were recruited to drive the simulated roadway under CV and non-CV environments. In the CV scenario, drivers were informed about the pavement conditions and the advisory speeds before entering HCs. In contrast, no messages were given to non-CV drivers. Truck drivers' behaviors in both scenarios were quantified using four Kinematic-based Surrogate Measures of Safety (K-SMoS), including deviation from the pathway, instantaneous acceleration, lateral speed, and steering angle. CVs’ trajectories were statistically compared to non-CVs in terms of the central tendency and dispersion using the Wilcoxon Signed-Rank Test (WSRT) and Median Absolute Deviation (MAD), respectively. The results of WSRT depicted, under the effect of CV advisory/warning messages and throughout the slippery HC, the central tendency of four K-SMoS could be shifted toward zero by 23% up to 99%. This shifting is associated with a significant safety enhancement that potentially can reduce the likelihood of curve-related crashes on slippery HCs. It was revealed that the variation in drivers’ behavior on the slippery HC could be minimized in the CV environment, where 54% up to 95% reduction in the dispersions of four K-SMoS were observed, leading to more certainty in drivers’ behavior.     

From anticipation to behavioral intention: Insights into human processing of multiple retrieval cues in road traffic

Anticipation in road traffic enables safer and more comfortable driving. Anticipatory driving is achieved through effective retrieval of prior driving-relevant knowledge using mental models and appropriate cues. Knowing when and which retrieval cues have a critical impact on the anticipation process and how information compatibility affects anticipation can be the basis for supporting people in anticipating and appropriate behavior in road traffic.For generating in-depth insights into the processing of retrieval cues, a video-based experimental study was conducted combining specific compatible and incompatible retrieval cues in urban driving scenarios. From a driver's perspective, participants were asked to anticipate in a two-step approach (measuring low and high certainty anticipation) whether a vehicle ahead would enter their lane or turn onto another street due to a lane blockage ahead. Further, they choose their preferred behavioral intention (accelerate, decelerate or maintain speed). In general, drivers strived for coherent situation representation, and in this process, multiple retrieval cues influenced anticipation in different ways. Participants were more likely to be consistent in their anticipation response. That is, they tend to follow their first intention (equivalent low and high certainty anticipation for either lane change or turn) even in the presence of incompatible stimuli. Inconsistent compared to consistent anticipation responses, however, led to reduced subjective confidence, and in part to increased criticality. Not only anticipation but also intended behavior was influenced by retrieval cues. In accordance, the anticipation of others' behaviors can be considered a predictor of specific intended behavior in road traffic.     

Driving examiners’ views on data-driven assessment of test candidates: An interview study

Vehicles are increasingly equipped with sensors that capture the state of the driver, the vehicle, and the environment. These developments are relevant to formal driver testing, but little is known about the extent to which driving examiners would support the use of sensor data in their job. This semi-structured interview study examined the opinions of 37 driving examiners about data-driven assessment of test candidates. The results showed that the examiners were supportive of using data to explain their pass/fail verdict to the candidate. According to the examiners, data in an easily accessible form such as graphs of eye movements, headway, speed, or braking behavior, and color-coded scores, supplemented with camera images, would allow them to eliminate doubt or help them convince disagreeing test-takers. The examiners were skeptical about higher levels of decision support, noting that forming an overall picture of the candidate’s abilities requires integrating multiple context-dependent sources of information. The interviews yielded other possible applications of data collection and sharing, such as selecting optimal routes, improving standardization, and training and pre-selecting candidates before they are allowed to take the driving test. Finally, the interviews focused on an increasingly viable form of data collection: simulator-based driver testing. This yielded a divided picture, with about half of the examiners being positive and half negative about using simulators in driver testing. In conclusion, this study has provided important insights regarding the use of data as an explanation aid for examiners. Future research should consider the views of test candidates and experimentally evaluate different forms of data-driven support in the driving test.     

Roadside digital billboard advertisements: Effects of static,transitioning, and animated designs on drivers’ performance and attention

The aim of this study was to analyze and compare the effects of different types of digital billboard advertisements (DBAs) on drivers’ performance and attention allocation. Driver distraction is a major threat to driver safety. DBAs are one form of distraction in drivers’ outside environment. There are many different types of DBAs, such as static images, changing images, or videos. However, it is not clear to what extent each of these contributes to driver distraction. A total of 100 students participated in a controlled driving simulator experiment in an urban environment. Measures of driving performance were collected, as well as eye tracking and EEG as windows into attention allocation. The different types of DBAs investigated were static (a single image), transitioning (one static DBA replaces another), and animated (short videos). The statistical analysis demonstrated that there were significant differences in the effect of each type of DBA on drivers' performance (deviation from the center of the lane and reaction time), visual attention to the road (percent of fixations on the road, percent of fixations on DBAs, fixation duration on DBAs, and number of gazes on DBAs), and the EEG theta band and beta band. These results show that driving performance and attention to the road were both more negatively affected when drivers were exposed to transitioning and animated DBAs as compared to static DBAs. The results of this study provide guidance for the better design and regulation of DBAs in order to minimize driver distraction.     

Mapping drivers’ mental models of adaptive cruise control to performance

Driver support features (DSF) have the potential to improve safety, but they also change the driver-vehicle relationship —as well as their respective roles and responsibilities. To maximize safety, it is important to understand how drivers’ knowledge and understanding of these technologies—referred to as drivers’ mental models—impact performance and safety. This simulator study examined how drivers with different mental models of adaptive cruise control performed in edge cases. The study compared the responses of groups of drivers, with strong and weak mental models of ACC, established through a combination of screening, training, and exposure, in edge case situations in a high-fidelity driving simulator. In general, participants with strong mental models were faster than those with weak mental models to respond in edge-case situations—defined as cases where the ACC did not detect an approaching object, such as a slow-moving motorcycle. The performance deficits observed for drivers with weak mental models appear to reflect uncertainty surrounding how ACC will behave in edge cases.     

Examining the efficacy of improved traffic signs and markings at flashing-light-controlled grade crossings based on driving simulation and eye tracking systems

The majority of the collisions at grade crossings occurred at flashing-light-controlled grade crossings. Understanding drivers’ behaviors and visual performances in the process of approaching the crossings is the foundation of improving crossing safety. This study aims at utilizing driving simulation and eye tracking systems to investigate the efficacy of improved traffic signs and pavement markings (PSM) at flashing-light-controlled grade crossings. The improved signs and markings were modeled in a driving simulation system and tested with a series of flashing light trigger time (FLTT) ranging from 2 s to 6 s with 1 s interval increment. Foggy conditions and drivers’ genders and vocations were considered in experiment design. Thirty-six fully-licensed drivers between 30 and 48 years participated in the experiment. Several eye-movement and behavioral measures were adopted as reflections of the subjects’ performances, including the first fixation time on signs and signals and distance to stop line, total fixation duration, compliance rate, stop position, average speed at the stop line, maximum deceleration rate and brake response time. Results showed that compared with traditional grade crossings signs and pavement markings, drivers could perceive signs timelier and fixate on the flashing-light signal earlier in PSM, especially in the scenarios of earlier FLTTs. The improvement in fixation performance and sign design contributed to a higher stop compliance rate. Importantly, it was found that drivers would hesitate to decide whether to stop or cross facing with flashing red lights, which is similar to the dilemma zone of roadway intersections. Drivers were more likely to fall into the dilemma zones when FLTT was <4 s. When FLTT was 2 s, it was particularly difficult to stop in front of the stop line. Moreover, under a foggy condition, drivers had a difficulty in searching signs and had a longer brake response time compared with a clear condition. For the characteristics of drivers, male drivers had longer fixation duration on signs than females. Professional drivers had a higher maximum deceleration rate compared with non-professional drivers. Above findings implied that improved traffic signs and markings would have a potential to improve traffic safety and deserve a field implementation in the future.     

Differential effects of driver sleepiness and sleep inertia on driving behavior

ObjectivesDriver sleepiness is one of the major safety issues in conventional driving and sleep inertia emerges as a driver state in automated driving. The aim of the present study was to assess the differential impacts of sleepiness and sleep inertia on driving behavior.Method61 participants completed a 10-min manual driving task during an otherwise automated drive. They completed the task (a) under an alert state, (b) under a sleepy state, and (c) after EEG-confirmed sleep. Driving performance was assessed with the parameters lane-keeping, speed choice, and speed-keeping. The eye-blink-based sleepiness measure PERCLOS (the proportion of time with eyes closed) was compared for the three driver states.ResultsLane- and speed-keeping performance were impaired under the sleepy state and after sleep, relative to the alert state. After sleep, lane-keeping behavior recovered rapidly and speed-keeping recovered by trend. Under the sleepy state, performance deteriorated. After sleep, the mean speed was lower than in the sleepy state and in the alert state. PERCLOS was increased after sleep and under the sleepy state, relative to the alert state.ConclusionsAlthough sleep inertia had detrimental effects on driving parameters similar to sleepiness, this effect rapidly vanished. Hence, while brief naps might be suitable to restore alertness in general, the minimal time needed to regain full capacity after napping should be a focus of future research.     

Influence of the median opening length on driving behaviors in the crossover work zone—A driving simulation study

Work zone safety has been a major concern for drivers and transportation agencies. Considering the severe consequences of crossover work zone crashes coupled with the limited literature on the median opening length, this paper aims to investigate the influence of the median opening length on driving behaviors from a behavioral perspective in crossover work zones. A driving simulation study with 32 participants was carried out to investigate the driving performance by metrics (speed, acceleration, maximum steering wheel speed, and lane-changing trajectory) with respect to five median opening lengths. The significant differences of each driving performance metric among various median opening lengths were found in the process of crossing through the median opening on the entrance by-pass and exit by-pass. The results indicated that drivers’ speeds were always higher than the speed limits for all median opening lengths. A narrower median opening may induce risky driving behaviors such as sharp deceleration and decelerating while lane-changing, which may increase speed variance. When crossing through the median opening with a larger length, high speed variance, sluggish lane-changing operations, and improper lane-using behaviors were observed because the excessive lane-changing space provided by the larger median opening length would decrease the situation awareness and increase the speed preference heterogeneity among drivers. Finally, some traffic management strategies were proposed, which can improve the safety and mobility of crossover work zones and further provide a basis for the formulation of related standards.     

Sandstorm animations on rural expressways: The impact of variable message sign strategies on driver behavior in low visibility conditions

Problem: Evolving sandstorms on rural expressways in desert countries impair drivers' contrast vision and increase the risk of serious crashes due to delayed speed adjustments. Intelligent Transport Systems (ITS) such as Variable Message Signs (VMS) conveying warnings can be activated to address drivers’ speed adaptation before entering a low visibility zone. To improve drivers’ understanding of the hazard, a sandstorm animation visualizing turbulent sand and its consequences was designed and compared with a general warning pictogram, which is applied if no specific weather pictogram is available. Moreover, minimum warning distances of the VMS to the low visibility zone were tested (e.g., 300 m or 500 m).MethodSixty-three participants from the State of Qatar drove in a driving simulator through clear, transition, and low visibility conditions on a rural expressway. A repeated analysis of variances was conducted to examine the impact of the two on-road warning displays on driving behavior.ResultsThe results showed that the sandstorm animation was similarly effective as a generic warning pictogram in reducing driving speeds before entering the transition and low visibility zone, irrespective of being displayed 500 m or 300 m away. However, the sandstorm animation resulted in consistent similar speed reductions within the low visibility zone, whereas the generic warning pictogram did either perform better or worse after several encounters with a sandstorm. Drivers did strongly agree that the animation is clearly referring to the issue of low visibility, which can be beneficial for recurring low visibility conditions.Practical applications: 1.) Displaying a sandstorm animation is beneficial for rural expressway sections with recurring degrading visibility and low traffic densities, whereas a warning pictogram can be more effective in speed reductions if drivers expect additional traffic hazards. 2.) Roadway authorities have the flexibility to activate a VMS sandstorm warning even for minimum warning distances.