Simulator evaluation of drivers’ speed,deceleration and lateral position at rural intersections in relation to different perceptual cues

Aim of the study was to investigate, by means of a driving simulator experiment, drivers’ behaviour in terms of speed, deceleration, and lateral position on major approaches of rural intersections in relation to different perceptual cues.In the experiment, ten different design conditions with and without speed-reducing treatments along the approach to the intersection were tested. Twenty-three drivers drove a test route two times and data from the second drive were used for comparison. The order of the ten design conditions was counterbalanced for all the drivers to minimize the presentation order effect. Three different data analysis techniques were used: (a) cluster analysis of speed and lateral position data, (b) statistical tests of speed and lateral position data, and (c) categorical analysis of deceleration behaviour patterns.The most effective treatments were the dragon teeth markings (based on the principle of optical road narrowing), the colored intersection area (based on the principle of intersection highlighting), and the raised median island (based on the principle of physical road narrowing). These measures, in comparison to the base intersection, produced: (1) a significant speed reduction starting from 250 m before the intersection in the range between 13 and 23 km/h, (2) a significant change in the deceleration behaviour with a reduction in the proportion of drivers which did not decelerate, and (3) a shift away from the intersection of the deceleration beginning. Given the significant effects on drivers’ behaviour, the dragon teeth markings, the colored intersection area, and the raised median island are strongly recommended for real world implementation.     

The effects of on-street parking and road environment visual complexity on travel speed and reaction time

On-street parking is associated with elevated crash risk. It is not known how drivers’ mental workload and behaviour in the presence of on-street parking contributes to, or fails to reduce, this increased crash risk. On-street parking tends to co-exist with visually complex streetscapes that may affect workload and crash risk in their own right. The present paper reports results from a driving simulator study examining the effects of on-street parking and road environment visual complexity on driver behaviour and surrogate measures of crash risk. Twenty-nine participants drove a simulated urban commercial and arterial route. Compared to sections with no parking bays or empty parking bays, in the presence of occupied parking bays drivers lowered their speed and shifted their lateral position towards roadway centre to compensate for the higher mental workload they reported experiencing. However, this compensation was not sufficient to reduce drivers’ reaction time on a safety-relevant peripheral detection task or to an unexpected pedestrian hazard. Compared to the urban road environments, the less visually complex arterial road environment was associated with speeds that were closer to the posted limit, lower speed variability and lower workload ratings. These results support theoretical positions that proffer workload as a mediating variable of speed choice. However, drivers in this study did not modify their speed sufficiently to maintain safe hazard response times in complex environments with on-street parking. This inadequate speed compensation is likely to affect real world crash risk.     

Experimental research on the effectiveness of speed reduction markings based on driving simulation: A case study

The objective of this paper is to test the effectiveness of speed reduction markings (SRMs). The empirical data including vehicle operations and drivers’ psychological and physical reactions were collected in a driving simulator. An index—the relative speed difference—was developed to evaluate the effectiveness of speed reduction markings. Researchers analyzed data to test the effectiveness of speed reduction markings and quantitatively study their effects and the deceleration process. Out of 15 subjects, there were 1 (7%), 2 (13%), and 7 (47%) subjects who decelerated while driving through the downhill section in the No SRMs scenario, Longitudinal SRMs scenario and Transverse SRMs scenario, respectively. In terms of speed and subjects’ decelerating maneuver, the results of the analysis of variance (ANOVA) and the contrast analysis (S–N–K method) showed that transverse speed reduction markings (TSRMs) could significantly influence subjects’ speed choice and maneuver (P < 0.05).     

Landscape heritage objects’ effect on driving: A combined driving simulator and questionnaire study

According to the literature, landscape (panoramas, heritage objects e.g. landmarks) affects people in various ways. Data are primarily developed by asking people (interviews, photo sessions, focus groups) about their preferences, but to a lesser degree by measuring how the body reacts to such objects. Personal experience while driving a car through a landscape is even more rare. In this paper we study how different types of objects in the landscape affect drivers during their drive. A high-fidelity moving-base driving simulator was used to measure choice of speed and lateral position in combination with stress (heart rate measure) and eye tracking. The data were supplemented with questionnaires. Eighteen test drivers (8 men and 10 women) with a mean age of 37 were recruited. The test drivers were exposed to different new and old types of landscape objects such as 19th century church, wind turbine, 17th century milestone and bus stop, placed at different distances from the road driven. The findings are in some respect contradictory, but it was concluded that that 33% of the test drivers felt stressed during the drive. All test drivers said that they had felt calm at times during the drive but the reason for this was only to a minor degree connected with old and modern objects. The open landscape was experienced as conducive to acceleration. Most objects were, to a small degree, experienced (subjective data) as having a speed-reducing effect, much in line with the simulator data (objective data). Objects close to the road affected the drivers’ choice of’ lateral position. No significant differences could be observed concerning the test drivers’ gaze between old or modern objects, but a significant difference was observed between the test drivers’ gaze between road stretches with faraway objects and stretches without objects. No meaningful, significant differences were found for the drivers’ stress levels as measured by heart rate.     

Age, skill, and hazard perception in driving

This study examined the effects of age and driving experience on the ability to detect hazards while driving; namely, hazard perception. Studies have shown that young-inexperienced drivers are more likely than experienced drivers to suffer from hazard perception deficiencies. However, it remains to be determined if this skill deteriorates with advancing age. Twenty-one young-inexperienced, 19 experienced, and 16 elderly drivers viewed six hazard perception movies while connected to an eye tracking system and were requested to identify hazardous situations. Four movies embedded planned, highly hazardous, situations and the rest were used as control. Generally, experienced and older-experienced drivers were equally proficient at hazard detection and detected potentially hazardous events (e.g., approaching an intersection, pedestrians on curb) continuously whereas young-inexperienced drivers stopped reporting on hazards that followed planned, highly hazardous situations. Moreover, while approaching T intersections older and experienced drivers fixated more towards the merging road on the right while young-inexperienced drivers fixated straight ahead, paying less attention to potential vehicles on the merging road. The study suggests that driving experience improves drivers’ awareness of potential hazards and guides drivers’ eye movements to locations that might embed potential risks. Furthermore, advanced age hardly affects older drivers’ ability to perceive hazards, and older drivers are at least partially aware of their age-related limitations.     

Cross-cultural differences in drivers’ speed choice

The aim of the present study was to examine if there are any cross-cultural differences between Swedish and Turkish drivers’ rating of the variables in the theory of planned behaviour (TPB) with regard to complying with the speed limit. A sample of 219 Swedish and 252 Turkish drivers completed a questionnaire including questions based on the theory of planned behaviour (i.e. regarding attitude, subjective norm, perceived behavioural control, intention and behaviour). The results show that country differences in drivers’ intention to comply with the speed limit as well as their self-reported compliance could be explained by differences found in their attitude, subjective norm and perceived behavioural control. Furthermore, drivers who live in a country with fewer road traffic fatalities (i.e. Sweden), compared with drivers who live in a country with more road traffic fatalities (i.e. Turkey), reported a more positive attitude towards complying with the speed limit, a more positive subjective norm, a higher perceived behavioural control, a higher intention and a larger proportion of the time spent complying.     

How to present collision warnings at intersections?—A comparison of different approaches

Analyses of intersection accidents have shown that in most cases drivers overlook or see other road users with the right of way too late that they cannot react in time. Appropriate visual warning signals which support drivers in their attention allocation and driving behavior could be useful to improve drivers’ reaction. In a driving simulator study, two warning strategies varying in their timing: (1) top-down warning while approaching a critical intersection and (2) bottom-up warning directly before the critical incident were investigated in a T-intersection situation. For the bottom-up warning, two warning signal designs were compared. 48 subjects (M = 27.3 years, SD = 7.4 years) participated in the study. Driving data as well as subjective evaluation of the three warning signals (one early and two late warning signals) were analyzed. The early warning signal which was given while approaching the intersection showed a positive effect. Here, most collisions could be avoided due to drivers’ adaptation of their driving behavior toward safer driving. They waited longer at the intersection before turning and finally turned with a lower velocity. In addition, drivers evaluated the early warning signal as very “useful”. With regard to the late warnings a much smaller effect was found. From these results, requirements can be derived for the design of effective warning strategies when driving at critical intersections.     

Development and evaluation of a Driving Observation Schedule (DOS) to study everyday driving performance of older drivers

This paper describes the development and evaluation of an on-road procedure, the Driving Observation Schedule (DOS), for monitoring individual driving behavior. DOS was developed for use in the Candrive/Ozcandrive five-year prospective study of older drivers. Key features included observations in drivers’ own vehicles, in familiar environments chosen by the driver, with start/end points at their own homes. Participants were 33 drivers aged 75+ years, who drove their selected route with observations recorded during intersection negotiation, lane-changing, merging, low speed maneuvers and maneuver-free driving. Driving behaviors were scored by a specialist occupational therapy driving assessor and another trained observer. Drivers also completed a post-drive survey about the acceptability of DOS. Vehicle position, speed, distance and specific roadways traveled were recorded by an in-vehicle device installed in the participant's vehicle; this device was also used to monitor participants’ driving over several months, allowing comparison of DOS trips with their everyday driving. Inter-rater reliability and DOS feasibility, acceptability and ecological validity are reported here. On average, drivers completed the DOS trip in 30.48 min (SD = 7.99). Inter-rater reliability measures indicated strong agreement between the trained and the expert observers: intra-class correlations (ICC) = 0.905, CI 95% 0.747–0.965, p < 0.0001; Pearson product correlation, r (18) = .83, p < 0.05. Standard error of the measurement (SEM), method error (ME) and coefficient of variation (CV) measures were consistently small (3.0, 2.9 & 3.3%, respectively). Most participants reported being ‘completely at ease’ (82%) with the driving task and ‘highly familiar with the route’ (97%). Vehicle data showed that DOS trips were similar to participants’ everyday driving trips in roads used, roadway speed limits, drivers’ average speed and speed limit compliance. In summary, preliminary findings suggest that DOS can be scored reliably, is of feasible duration, is acceptable to drivers and representative of everyday driving. Pending further research with a larger sample and other observers, DOS holds promise as a means of quantifying and monitoring changes in older drivers’ performance in environments typical of their everyday driving.     

Additional road markings as an indication of speed limits: Results of a field experiment and a driving simulator study

Although speed limits are indicated by road signs, road users are not always aware, while driving, of the actual speed limit on a given road segment. The Roads and Traffic Agency developed additional road markings in order to support driver decisions on speed on 70 km/h roads in Flanders-Belgium. In this paper the results are presented of two evaluation studies, both a field study and a simulator study, on the effects of the additional road markings on speed behaviour. The results of the field study showed no substantial effect of the markings on speed behaviour. Neither did the simulator study, with slightly different stimuli. Nevertheless an effect on lateral position was noticed in the simulator study, showing at least some effect of the markings. The role of conspicuity of design elements and expectations towards traffic environments is discussed. Both studies illustrate well some strengths and weaknesses of observational field studies compared to experimental simulator studies.     

Classification analysis of driver's stop/go decision and red-light running violation

When the driver encounters a signal change from green to yellow, he is required to make a stop or go decision based on his speed and the distance to the stop bar making the wrong decision will lead to a red-light running violation or an abrupt stop at the intersection. In this study, a field data collection was conducted at a high-speed signalized intersection, where a video-based system with three cameras was used to record the drivers’ behavior related to the onset of yellow. Observed data include drivers’ stop/go decisions, red-light running violation, lane position in the highway, positions (leading/following) in the traffic flow, vehicle type, and vehicles’ yellow-onset speeds and distances from the intersection. Further, classification tree models were applied to analyze how the probabilities of a stop or go decision and of red-light running are associated with the traffic parameters. The data analysis indicated that vehicle's distance from the intersection at the onset of yellow, operating speed, and position in the traffic flow are the most important predictors for both the stop/go decision and red-light running violation. This study illustrates that the tree models are helpful to recognize and predict how drivers make stop/go decisions and partake in red-light running violations corresponding to the traffic parameters.     

The impact of tunnel design and lighting on the performance of attentive and visually distracted drivers

The crash risk in tunnels is lower than on the open road network, but the consequences of a crash are often severe. Proper tunnel design is one measure to reduce the likelihood of crashes, and the objective of this work is to investigate how driving performance is influenced by design factors, and whether there is an interaction with secondary task load. Twenty-eight drivers participated in the simulator study. A full factorial within subject design was used to investigate the tunnel wall colour (dark or light-coloured walls), illumination (three different levels) and task load (with or without a visual secondary task). The results show that tunnel design and illumination have some influence on the drivers’ behaviour, but visual attention given to the driving task is the most crucial factor, giving rise to significant changes in both driving behaviour and visual behaviour. The results also indicate that light-coloured tunnel walls are more important than strong illumination to keep the drivers’ visual attention focused forward.     

Commentary training improves responsiveness to hazards in a driving simulator

Can commentary driving produce safer drivers? Producing a verbal commentary of potential hazards during driving has long been considered by the police to improve hazard perception skills. In this study we investigated whether learner drivers would benefit from being trained to produce a commentary drive. All learners were initially assessed on a virtual route in a driving simulator that contained 9 hazards. One group of drivers was then trained in commentary driving, and their subsequent simulated driving behaviour was compared to a control group. The results showed that the trained group had fewer crashes, reduced their speed sooner on approach to hazards, and applied pressure to the brakes sooner than untrained drivers. Conversely the untrained drivers’ behaviour on approach to hazards was symptomatic of being surprised at the appearance of the hazards. The benefit of training was found to be greater for certain types of hazard than others.     

Reliability of drivers in urban intersections

The concept of human reliability has been widely used in industrial settings by human factors experts to optimise the person-task fit. Reliability is estimated by the probability that a task will successfully be completed by personnel in a given stage of system operation. Human Reliability Analysis (HRA) is a technique used to calculate human error probabilities as the ratio of errors committed to the number of opportunities for that error. To transfer this notion to the measurement of car driver reliability the following components are necessary: a taxonomy of driving tasks, a definition of correct behaviour in each of these tasks, a list of errors as deviations from the correct actions and an adequate observation method to register errors and opportunities for these errors. Use of the SAFE-task analysis procedure recently made it possible to derive driver errors directly from the normative analysis of behavioural requirements. Driver reliability estimates could be used to compare groups of tasks (e.g. different types of intersections with their respective regulations) as well as groups of drivers’ or individual drivers’ aptitudes. This approach was tested in a field study with 62 drivers of different age groups. The subjects drove an instrumented car and had to complete an urban test route, the main features of which were 18 intersections representing six different driving tasks. The subjects were accompanied by two trained observers who recorded driver errors using standardized observation sheets. Results indicate that error indices often vary between both the age group of drivers and the type of driving task. The highest error indices occurred in the non-signalised intersection tasks and the roundabout, which exactly equals the corresponding ratings of task complexity from the SAFE analysis. A comparison of age groups clearly shows the disadvantage of older drivers, whose error indices in nearly all tasks are significantly higher than those of the other groups. The vast majority of these errors could be explained by high task load in the intersections, as they represent difficult tasks. The discussion shows how reliability estimates can be used in a constructive way to propose changes in car design, intersection layout and regulation as well as driver training.     

At the cross-roads: An on-road examination of driving errors at intersections

A significant proportion of road trauma occurs at intersections. Understanding the nature of driving errors at intersections therefore has the potential to lead to significant injury reductions. To further understand how the complexity of modern intersections shapes behaviour of these errors are compared to errors made mid-block, and the role of wider systems failures in intersection error causation is investigated in an on-road study. Twenty-five participants drove a pre-determined urban route incorporating 25 intersections. Two in-vehicle observers recorded the errors made while a range of other data was collected, including driver verbal protocols, video, driver eye glance behaviour and vehicle data (e.g., speed, braking and lane position). Participants also completed a post-trial cognitive task analysis interview. Participants were found to make 39 specific error types, with speeding violations the most common. Participants made significantly more errors at intersections compared to mid-block, with misjudgement, action and perceptual/observation errors more commonly observed at intersections. Traffic signal configuration was found to play a key role in intersection error causation, with drivers making more errors at partially signalised compared to fully signalised intersections.     

Intelligent speed adaptation—Effects and acceptance by young inexperienced drivers

This study assessed the relative effects of two intelligent speed adaptation (ISA) systems (informative and actively supporting) on simulated driving performance and acceptability in a sample of inexperienced and experienced drivers. Participants drove a series of simulated drives under three conditions: no ISA (control), ISA informative and ISA actively supporting. The informative system significantly reduced speed and was particularly effective in reducing top-end speeds. Comparable reductions were not found for the actively supporting system. Differences in the effectiveness and acceptability of ISA systems were noted across experienced and inexperienced drivers. The ISA systems appeared more effective at reducing speeds for experienced drivers on some road types. Experienced drivers’ subjective satisfaction ratings of the systems also remained constant over the trial, whereas the inexperienced drivers’ ratings changed after experience. There was little evidence that drivers engaged in negative behavioral adaptation and no evidence that subjective workload levels increased with ISA use. Future directions for examining the safety benefits of ISA, particularly for inexperienced drivers, are discussed.     

Driver's visual attention as a function of driving experience and visibility. Using a driving simulator to explore drivers’ eye movements in day, night and rain driving

Road crashes are the main cause of death of young people in the developed world. The reasons that cause traffic crashes are numerous; however, most researchers agree that a lack of driving experience is one of the major contributing factors. In addition it has been demonstrated that environmental factors such as driving during night and rain increases the risk of a crash. Both of these factors may be related to drivers’ visual search strategies that become more efficient with increased experience.In the present study we recorded the eye movements of driving instructors and learner drivers while they drove three virtual routes that included day, night and rain routes in a driving simulator.The results showed that driving instructors had an increased sampling rate, shorter processing time and broader scanning of the road than learner drivers. This broader scanning of the road could be possibly explained by the mirror inspection pattern which revealed that driving instructors fixated more on the side mirrors than learner drivers. Also it was found that poor visibility conditions, especially rain, decrease the effectiveness of drivers’ visual search. The lack of interaction between driving experience and visibility suggests that some aspects of visual search are affected by general rather than situation specific driving experience.The present findings support the effect of driving experience in modifying eye movement strategies. The high accident risk of night and rain driving could be partly explained by the decrement in visual search strategies during these conditions. Finally it is argued that the use of driving simulators can provide valuable insights regarding driving safety.     

Older drivers' insight into their hazard perception ability

Even though the driving ability of older adults may decline with age, there is evidence that some individuals attempt to compensate for these declines using strategies such as restricting their driving exposure. Such compensatory mechanisms rely on drivers’ ability to evaluate their own driving performance. This paper focuses on one key aspect of driver ability that is associated with crash risk and has been found to decline with age: hazard perception. Three hundred and seven drivers, aged 65–96, completed a validated video-based hazard perception test. There was no significant relationship between hazard perception test response latencies and drivers’ ratings of their hazard perception test performance, suggesting that their ability to assess their own test performance was poor. Also, age-related declines in hazard perception latency were not reflected in drivers’ self-ratings. Nonetheless, ratings of test performance were associated with self-reported regulation of driving, as was self-rated driving ability. These findings are consistent with the proposal that, whileself-assessments of driving ability may be used by drivers to determine the degree to which they restrict their driving, the problem is that drivershave little insight into their own driving ability. This may impact on the potential road safety benefits of self-restriction of driving because drivers may not have the information needed to optimally self-restrict. Strategies for addressing this problem are discussed.     

What does the driver look at? The influence of intersection characteristics on attention allocation and driving behavior

One of the main contributing factors with intersection accidents is lack of information due to attention allocation. In many cases, drivers fail to yield right of way to other traffic participants. One reason is that drivers have inappropriate expectations about a traffic situation. They allocate their attention primarily to certain areas of the intersection but neglect others. In a driving simulator study, the influence of intersection complexity on drivers’ expectations and their driving behavior was examined. In two T-intersections, the complexity was varied by the traffic density (low and high) using either one or two important objects: vehicles (left) with or without pedestrians (right). Additionally, the reaction to two critical incidents in close proximity of the intersections was examined. Gaze behavior, vehicle reactions, and subjective data were recorded. 40 subjects (26 male, 14 female, M = 31.0 years, SD = 11.9 years) participated in the study. Interestingly, the least complex intersections showed the most accidents which was interpreted as the result of inadequate attention allocation. It was shown that both the drivers’ attention allocation and vehicle velocity when turning off were responsible for this effect. The results contribute to a better understanding of the role of drivers’ expectation and attention allocation in the causation of intersection accidents.