Age differences in simulated driving performance: Compensatory processes

In the context of driving, the reported experiment examines compensatory processes for age-related declines in cognitive ability. Younger (26–40 years) and older (60+ years) participants (n = 22 each group) performed a car following task in a driving simulator. Several performance measures were recorded, including assessments of anticipation of unfolding traffic events. Participants also completed a range of measures of cognitive ability – including both fluid and crystallised abilities. Three examples of age-related compensation are reported: (i) older drivers adopted longer headways than younger drivers. Data were consistent with this being compensation for an age-related deficit in complex reaction time; (ii) older drivers with relatively higher cognitive ability anticipated traffic events more frequently, whereas the reverse pattern was found for younger drivers; and, (iii) older drivers with greater crystallised ability were less reliant on spatial ability to maintain lane position. Consistent with theories of ‘cognitive reserve’, interactions between crystallised ability and age for self-report workload suggested that compensation for age-related cognitive ability deficits required investment of additional effort. Results are considered in the context of the prospects of further assessment of older drivers.     

Investigating the influence of working memory capacity when driving behavior is combined with cognitive load: An LCT study of young novice drivers

Distracted driving has received increasing attention in the literature due to potential adverse safety outcomes. An often posed solution to alleviate distraction while driving is hands-free technology. Interference by distraction can occur however at the sensory input (e.g., visual) level, but also at the cognitive level where hands-free technology induces working memory (WM) load. Active maintenance of goal-directed behavior in the presence of distraction depends on WM capacity (i.e., Lavie's Load theory) which implies that people with higher WM capacity are less susceptible to distractor interference. This study investigated the interaction between verbal WM load and WM capacity on driving performance to determine whether individuals with higher WM capacity were less affected by verbal WM load, leading to a smaller deterioration of driving performance. Driving performance of 46 young novice drivers (17–25 years-old) was measured with the lane change task (LCT). Participants drove without and with verbal WM load of increasing complexity (auditory-verbal response N-back task). Both visuospatial and verbal WM capacity were investigated. Dependent measures were mean deviation in the lane change path (MDEV), lane change initiation (LCI) and percentage of correct lane changes (PCL). Driving experience was included as a covariate. Performance on each dependent measure deteriorated with increasing verbal WM load. Meanwhile, higher WM capacity related to better LCT performance. Finally, for LCI and PCL, participants with higher verbal WM capacity were influenced less by verbal WM load. These findings entail that completely eliminating distraction is necessary to minimize crash risks among young novice drivers.     

Effects of work zone configurations and traffic density on performance variables and subjective workload

This paper investigates the effect of changing work zone configurations and traffic density on performance variables and subjective workload. Data regarding travel time, average speed, maximum percent braking force and location of lane changes were collected by using a full size driving simulator. The NASA-TLX was used to measure self-reported workload ratings during the driving task. Conventional lane merge (CLM) and joint lane merge (JLM) were modeled in a driving simulator, and thirty participants (seven female and 23 male), navigated through the two configurations with two levels of traffic density. The mean maximum braking forces was 34% lower in the JLM configuration, and drivers going through the JLM configuration remained in the closed lane longer. However, no significant differences in speed were found between the two merge configurations. The analysis of self-reported workload ratings show that participants reported 15.3% lower total workload when driving through the JLM. In conclusion, the implemented changes in the JLM make it a more favorable merge configuration in both high and low traffic densities in terms of optimizing traffic flow by increasing the time and distance cars use both lanes, and in terms of improving safety due to lower braking forces and lower reported workload.     

In the eye of the beholder: A simulator study of the impact of Google Glass on driving performance

This study examined whether, and to what extent, driving is affected by reading text on Google Glass. Reading text requires a high level of visual resources and can interfere with safe driving. However, it is currently unclear if the impact of reading text on a head-mounted display, such as Google Glass (Glass), will differ from that found with more traditional head-down electronic devices, such as a dash-mounted smartphone. A total of 20 drivers (22–48 years) completed the Lane Change Test while driving undistracted and while reading text on Glass and on a smartphone. Measures of lateral vehicle control and event detection were examined along with subjective workload and secondary task performance. Results revealed that drivers’ lane keeping ability was significantly impaired by reading text on both Glass and the smartphone. When using Glass, drivers also failed to detect a greater number of lane change signs compared to when using the phone or driving undistracted. In terms of subjective workload, drivers rated reading on Glass as subjectively easier than on the smartphone, which may possibly encourage greater use of this device while driving. Overall, the results suggest that, despite Glass allowing drivers to better maintain their visual attention on the forward scene, drivers are still not able to effectively divide their cognitive attention across the Glass display and the road environment, resulting in impaired driving performance.     

Development of crash modification factors for changing lane width on roadway segments using generalized nonlinear models

This study evaluates the effectiveness of changing lane width in reducing crashes on roadway segments. To consider nonlinear relationships between crash rate and lane width, the study develops generalized nonlinear models (GNMs) using 3-years crash records and road geometry data collected for all roadway segments in Florida. The study also estimates various crash modification factors (CMFs) for different ranges of lane width based on the results of the GNMs. It was found that the crash rate was highest for 12-ft lane and lower for the lane width less than or greater than 12 ft. GNMs can extrapolate this nonlinear continuous effect of lane width and estimate the CMFs for any lane width, not only selected lane widths, unlike generalized linear models (GLMs) with categorical variables. The CMFs estimated using GNMs reflect that crashes are less likely to occur for narrower lanes if the lane width is less than 12 ft whereas crashes are less likely to occur for wider lanes if the lane width is greater than 12 ft. However, these effects varied with the posted speed limits as the effect of interaction between lane width and speed limit was significant. The estimated CMFs show that crashes are less likely to occur for lane widths less than 12 ft than the lane widths greater than 12 ft if the speed limit is higher than or equal to 40 mph. It was also found from the CMFs that crashes at higher severity levels (KABC and KAB) are less likely to occur for lane widths greater or less than 12 ft compared to 12-ft lane. The study demonstrates that the CMFs estimated using GNMs clearly reflect variations in crashes with lane width, which cannot be captured by the CMFs estimated using GLMs. Thus, it is recommended that if the relationship between crash rate and lane width is nonlinear, the CMFs are estimated using GNMs.     

Impact of distracted driving on safety and traffic flow

Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16–25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) Poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner that impacts safety and traffic flow negatively when distracted.     

经验因素与车道类型对汽车驾驶员变道决策的影响

目的考察驾驶经验与车道类型对驾驶员变道决策的影响以及不同经验驾驶员的眼动注意搜索模式。方法使用Tobii眼动仪和驾驶场景视频收集了35名驾驶员的变道决策反应时、变道频率及眼动数据。结果驾驶经验与车道类型对驾驶员变道决策反应时交互作用显著;驾驶经验、车道类型与兴趣区对驾驶员总注视时间交互作用显著,同时驾驶员前方视野总注视时间对其边侧车道变道决策反应时有负向预测作用。结论中间车道条件下,实习驾驶员变道决策反应时更慢;边侧车道条件下结论相反;中间车道条件下,实习驾驶员对于侧视镜的总注视时间更长;边侧车道条件下,实习驾驶员对于前方视野的总注视时间更长;边侧车道条件下,实习驾驶员对于前方视野注视时间越长,变道决策反应时越快,这可以被视为实习驾驶员变道决策反应时更快的主要视觉注意机制。本研究对驾驶员改善变道行为和安全驾驶具有重要意义。     

Aggressive driving: an observational study of driver, vehicle, and situational variables

Over 2000 aggressive driving behaviors were observed over a total of 72 h at six different sites. The behaviors selected for observation were those that are commonly included in "aggressive driving" lists, and they consisted of honking, cutting across one or more lanes in front of other vehicles, and passing on the shoulders. In addition, an exposure sample of 7200 drivers were also observed at the same times and places. Relative risks (RRs) and odds ratios (ODs) were calculated to show the relative likelihood that different drivers under different conditions will commit aggressive behaviors. The rate of aggressive actions observed in this study decreased from the most frequent behavior of cutting across a single lane, through honking, and to the least frequent behaviors of cutting across multiple lanes and passing on the shoulders. Relative to their proportion in the driving population, men were more likely than women to commit aggressive actions, and the differences increased as the severity of the action increased. Drivers who were 45 years old or older were less likely to drive aggressively than younger ones. The presence of passengers was associated with a slight but consistent reduction in aggressive driving of all types; especially honking at other drivers. There was a strong linear association between congestion and the frequency of aggressive behaviors, but it was due to the number of drivers on the road. However, when the value of time was high (as in rush hours), the likelihood of aggressive driving--after adjusting for the number of drivers on the road--was higher than when the value of time was low (during the non-rush weekday or weekend hours). The results have implications for driver behavior modifications and for environmental design.     

Validity and reliability of the on-road driving assessment with senior drivers

The on-road driving assessment is widely regarded as the criterion measure for driving performance despite a paucity of evidence concerning its psychometric properties. The purpose of this study was 2-fold. First, we examined the psychometric properties of an on-road driving assessment with 100 senior drivers between 60 and 86 years (80 healthy volunteers and 20 with specific vision deficits) using Rasch modeling. Second, we compared the outcome of the gestalt decision made by trained professionals with that based on weighted error scores from the standardized assessment. Rasch analysis provided good evidence for construct validity and inter-rater reliability of the on-road assessment and some evidence for internal reliability. Goodness of fit statistics for all items were within an acceptable range and the item hierarchy was logical. The test had a moderate reliability index (0.67). The best cut off score yielded sensitivity of 81% and specificity of 95% compared with the gestalt decision. Further research is required with less competent drivers to more fully examine reliability. Healthy senior drivers failed to check blind spots when changing lanes and made errors when asked to report road markings and traffic signs as they drove. In addition unsafe drivers had difficulty negotiating intersections and lane changes.     

Does attention capacity moderate the effect of driver distraction in older drivers?

With age, a decline in attention capacity may occur and this may impact driving performance especially while distracted. Although the effect of distraction on driving performance of older drivers has been investigated, the moderating effect of attention capacity on driving performance during distraction has not been investigated yet. Therefore, the aim was to investigate whether attention capacity has a moderating effect on older drivers’ driving performance during visual distraction (experiment 1) and cognitive distraction (experiment 2). In a fixed-based driving simulator, older drivers completed a driving task without and with visual distraction (experiment 1, N = 17, mean age 78 years) or cognitive distraction (experiment 2, N = 35, mean age 76 years). Several specific driving measures of varying complexity (i.e., speed, lane keeping, following distance, braking behavior, and crashes) were investigated. In addition to these objective driving measures, subjective measures of workload and driving performance were also included. In experiment 1, crash occurrence increased with visual distraction and was negatively related to attention capacity. In experiment 2, complete stops at stop signs decreased, initiation of braking at pedestrian crossings was later, and crash occurrence increased with cognitive distraction. Interestingly, for a measure of lane keeping (i.e., standard deviation of lateral lane position (SDLP)), effects of both types of distraction were moderated by attention capacity. Despite the decrease of driving performance with distraction, participants estimated their driving performance during distraction as good. These results imply that attention capacity is important for driving. Driver assessment and training programs might therefore focus on attention capacity. Nonetheless, it is crucial to eliminate driver distraction as much as possible given the deterioration of performance on several driving measures in those with low and high attention capacity.     

Driving strategies in overtaking

Over 400 overtaking manoeuvres were observed on a two lane British “A” carriageway with a maximum speed limit of 100 km/hr. It was found that 14% of overtaking drivers use a gap size too small (i.e. less than 400 m) to comfortably accommodate vehicles closing on each other at normally assumed driving speeds. Acceptance of a small gap for overtaking increased the incidence of lane sharing (overtaking partially in both lanes) and cutting in (precipitous return to the driving lane). When only a small gap was available, there was an increase in both lane sharing and cutting in, usually only one of the above options was utilised with a tendency for piggy-backers (two or more simultaneous overtakers) to prefer lane sharing while non-piggy-backers preferred to cut in. Flying overtakers (overtaking without pause), accelerative overtakers (overtaking after a pause), piggy-backers, non piggy-backers and drivers not braking to follow before overtaking, all cut in more in small gaps than in large gaps. Only drivers braking to follow failed to cut-in more in small gaps. In addition, accelerative overtakers, piggy-backers, non piggy-backers, drivers braking and drivers not braking to follow, lane shared more in small gaps than large gaps. Only flying overtakers failed to lane share more in small gaps than in large gaps, but this was because they did a lot of lane sharing in both large and small gaps. Finally, flying overtakers, piggy-backers and drivers who braked in order to follow before overtaking, were more likely to accept a small gap for overtaking than were accelerative overtakers, non piggy-backers and drivers who did not brake to follow. Policy and research implications of these findings are discussed.     

Merging into heavy motorway traffic by young and elderly drivers

An increase in the number of Heavy Goods Vehicles on motorways may lead to additional problems in the interaction with an increased number of elderly drivers. Elderly drivers suffer from reduced information processing speed and capacity, and in general effectively compensate for this by taking more time. However, this strategy, regulating task demands by slowing down will make merging into motorway traffic actually more difficult.In an experiment performed in a driving simulator, young and elderly drivers merged into motorway traffic. Driver behaviour and mental workload were studied while the following factors were manipulated: type of traffic and density of Heavy Goods Vehicles on the main road, the length of the acceleration lane, presence of a slowly driving lead car, and presence of a driver support system that encouraged the drivers to speed up if their speed was too low.Results show that the effects of an increased number of Heavy Goods Vehicles on the main road were not more adverse for elderly than for the young participants, with the exception that elderly drivers merged at a lower speed. This lower speed could make the manoeuvre more risky in real traffic. The support system and an extended acceleration lane facilitated merging, while a slowly driving lead car impeded completion of the manoeuvre.     

Driving with pets as a risk factor for motor vehicle collisions among older drivers

Increasing rates of distraction-related motor vehicle collisions (MVCs) continue to raise concerns regarding driving safety. This study sought to evaluate a novel driving-related distraction, driving with a pet, as a risk factor for MVCs among older, community dwelling adults. Two thousand licensed drivers aged 70 and older were identified, of whom 691 reported pet ownership. Comparing pet owners who did and did not drive with their pets, neither overall MVC rates (rate ratio [RR] 0.97, 95% confidence interval [CI] 0.75–1.26) nor at-fault MVC rates (RR 0.84, 95% CI 0.57–1.24) were elevated. However, those who reported always driving with a pet in the vehicle had an elevated MVC rate (RR 1.89, 95% CI 1.10–3.25), as compared to those who did not drive with a pet. The MVC rate was not increased for those reporting only sometimes or rarely driving with a pet in the vehicle. The current study demonstrates an increased risk of MVC involvement in those older drivers who always take a pet with them when they drive a vehicle. When confronted with an increased cognitive or physical workload while driving, elderly drivers in prior studies have exhibited slower cognitive performance and delayed response times in comparison to younger age groups. Further study of pet-related distracted driving behaviors among older drivers as well as younger populations with respect to driver safety and performance is warranted to appropriately inform the need for policy regulation on this issue.     

The visual control of bicycle steering: The effects of speed and path width

Although cycling is a widespread form of transportation, little is known about the visual behaviour of bicycle users. This study examined whether the visual behaviour of cyclists can be explained by the two-level model of steering described for car driving, and how it is influenced by cycling speed and lane width. In addition, this study investigated whether travel fixations, described during walking, can also be found during a cycling task. Twelve adult participants were asked to cycle three 15 m long cycling lanes of 10, 25 and 40 cm wide at three different self-selected speeds (i.e., slow, preferred and fast). Participants’ gaze behaviour was recorded at 50 Hz using a head mounted eye tracker and the resulting scene video with overlay gaze cursor was analysed frame by frame. Four types of fixations were distinguished: (1) travel fixations, (2) fixations inside the cycling lane (path), (3) fixations to the final metre of the lane (goal), and (4) fixations outside of the cycling lane (external). Participants were found to mainly watch the path (41%) and goal (40%) region while very few travel fixations were made (<5%). Instead of travel fixations, an OptoKinetic Nystagmus was revealed when looking at the near path. Large variability between subjects in fixation location suggests that different strategies were used. Wider lanes resulted in a shift of gaze towards the end of the lane and to external regions, whereas higher cycling speeds resulted in a more distant gaze behaviour and more travel fixations. To conclude, the two-level model of steering as described for car driving is not fully in line with our findings during cycling, but the assumption that both the near and the far region is necessary for efficient steering seems valid. A new model for visual behaviour during goal directed locomotion is presented.     

Effect of shoulder width, guardrail and roadway geometry on driver perception and behavior

Roadway design is one of the most significant factors that affect driving behavior and perceived safety. The current study tests the combined effects of three roadway design elements – shoulders width, guardrail existence and roadway geometry (curvature) – on objective driving measures (speed and lane position), and subjective measures (perceived safe driving speed and estimated road safety).Twenty two drivers participated in an experiment with a driving simulation. In the first part objective driving data were collected, and in the second part subjective paper–pencil evaluations were requested of the perceived safety of 30 different scenarios that were previously experienced in the simulator. The scenarios consisted of the various combinations of the three roadway design elements.The results showed a significant effect of roadway geometry on both objective and subjective measures. The shoulders width had a significant effect on actual speed, on lane position, and on perceived safe driving speed, but only when a guardrail was present.These findings illustrate the perceptual role of a guardrail in defining the perceived safety margins that various shoulder widths provide. When a guardrail is absent, the width of the shoulder loses much of its benefits and effects on driving behavior. The results also demonstrate that roadway geometry can be used to reduce driving speeds, but at the same time it can have a negative effect on maintaining a stable lane position in sharp curves. Thus, controlling the width of road shoulders and the placement of guardrails seems to be a safer approach to speed and lane position control.     

The effect of cycle lanes on the proximity between motor traffic and cycle traffic

An experiment collected proximity data of motor traffic overtaking cycle traffic on roads with and without cycle lanes using an instrumented bicycle. The work enhances previous research which has considered the riding position of the cyclist and whether or not the cyclist was helmeted, while controlling for vehicle type.The analysis shows that significantly wider passing distances are adopted by motorists in the condition without a 1.45 m cycle lane, with posted speed limits of 40 mph and 50 mph with a 9.5 m wide carriageway. These findings were not replicated for a similar width road with a posted speed limit of 30 mph and a 1.3 m cycle lane.The results suggest that in the presence of a cycle lane, drivers may be driving within the confines of their own marked lane with less recognition being given to the need to provide a comfortable passing distance to cycle traffic in the adjacent cycle lane.     

The effect of chevron alignment signs on driver performance on horizontal curves with different roadway geometries

To develop a practicable and clear guideline for implementing Chevrons on China’s highways, it is necessary to understand the effect of Chevrons on driving performance in different roadway geometries.Using a driving simulator, this study tests the effect of China’s Chevrons on vehicle speed and lane position on two-lane rural highway horizontal curves with different roadway geometries.The results showed a significant effect of Chevrons on speed reduction, and this function was not significantly affected by curve radius but was statistically affected by curve direction. The speed reduction caused by Chevrons was also significant at the approach of curve, middle of curve and point of tangent. The 85th percentile speed was also markedly lower when Chevrons were present. We also found a significant effect of Chevrons in encouraging participants to drive the vehicle with a more proper lane position at the first half of curves; and this function was slightly affected by curve radius. Meanwhile, the effect of Chevrons on keeping drivers staying in a more stable lane position was also statistically significant at the second half of curves. In sharp curves, the function of Chevrons to make drivers keep a stable lane position was lost. Besides, the impact of curve direction on the function of Chevrons on lane position was always present, and drivers would drive slightly away from Chevrons.Regardless of the curve radius, China’s Chevrons at horizontal curves provide an advance warning, speed control and lane position guide for traffic on the nearside of Chevrons. Besides, combing with the function of Chevrons on preventing excessive speed and the benefit to make drivers keep a more proper lane position, China’s Chevrons appear to be of great benefit to reduce crashes (e.g., run-off-road) in curves.     

Driver's lane keeping ability with eyes off road: Insights from a naturalistic study

Many studies have shown that driver inattention can influence lane-keeping ability. The majority of studies on lane keeping have been conducted in controlled on-road networks or in simulated environments. However, few studies have examined lane-keeping ability in naturalistic settings for the same purpose. In this current study, the relationship between driver inattention and lane keeping ability was examined using naturalistic data for 24 drivers. Driver inattention was placed into two categories based on whether drivers were looking forward toward the roadway (inattention with eyes-on-road) or not looking forward (inattention with eyes-off-road) while engaged in a secondary task. Repeated measures regression models were used to account for within-subject correlations. The results showed that, after accounting for driving speed and lane width, the eyes-off-road significantly increased the standard deviation of lane position (SDLP). The findings from this study are consistent with other studies that show that the amount of time drivers spend looking away from the road can impact drivers’ ability to maintain their lane position. Additionally, this paper demonstrates how driver inattention can be examined with real world data while accounting for the roadway, environment, and driver behavior.     

Self-reported wayfinding ability of older drivers

Some older drivers experience difficulties driving whilst wayfinding in unfamiliar areas. Difficulties in wayfinding have been associated with poorer driving performance and reduced driving mobility. The objective of the current study was to identify cognitive and demographic predictors in older drivers of perceived wayfinding difficulty, avoidance of unfamiliar areas and the use of wayfinding strategies. Five hundred and thirty-four drivers aged 65 years and over (excluding those with dementia or Parkinson's disease) completed a mail-out survey. Drivers commonly reported difficulties with wayfinding, with 59.5% reporting their abilities as poor or fair rather than good. Those significantly more likely to report difficulty were older, reported poorer health and cognition, and had less driving experience. A small proportion of drivers reported regularly avoiding unfamiliar areas (13.8%); these drivers were significantly more likely to be female and to report poorer wayfinding abilities. The most common wayfinding strategies regularly used by older drivers were using a street directory whilst driving (61.9%) and pulling over to check the map (55.1%). Regular passenger guidance (23.9%) or use of a navigation system (9.9%) was less common. The implications of this study are wide and include collecting further information about: (1) the role of cognitive processes in wayfinding ability; (2) the relationship between perceived wayfinding difficulty and restriction of driving in unfamiliar areas; and (3) older drivers’ preferences for different wayfinding strategies.     

Lane heading difference: An innovative model for drowsy driving detection using retrospective analysis around curves

Driving while sleepy is a serious contributor to automobile accidents. Previous research has shown that drowsy drivers produce systematic errors (variability) in vehicle behavior which are detectable using vehicle monitoring technology. The current study developed a new methodological approach using a vehicle heading difference metric to detect drowsy driving more effectively than other more commonly used methods. Twenty participants completed a driving scenario as well as several measures of fatigue in five testing sessions across a night of sleep deprivation. Each simulated highway driving session lasted 20 min, and was analyzed for lateral lane position variability and vehicle heading difference variability with two statistical methods. Fatigue measures monitored reaction time, attention, and oculomotor movement. The results showed that examining lane heading difference using the absolute value of the raw data detected driving variability better across the night than other statistical models. The results from the fatigue measures indicated an increase in reaction time and response lapses, as well as a decrease in oculomotor reactivity across the night. These results suggest that in fatigued drivers the statistical model using the absolute value of lane heading could be an improved metric for drowsy driving detection that could accurately detect detriments in driving ability at lower levels of fatigue.