Latencies in Vehicle Steering: It is Possible to Measure Drivers’ Response Latencies and Attention Unobtrusively on the Road

This paper reviews results from a series of studies in which latencies in driver/ vehicle steering responses were measured on the road, unobtrusively, and with representative samples of unsuspecting drivers. Based on the fact that an obstacle on the road shoulder induces an avoidance response, i.e., a lateral displacement towards the middle of the road, a stimulus event was introduced at various distances when a car was approaching so that the time available to drivers for an avoidance response was known. It was found, first, that the average steering response started at latencies greater than 1 s, reached the half-way point at 2.5 s and the maximum at 3-4 s, depending on the situation. Second, this method was applied in a project on the effects of a warning flasher on driver behavior in school zones. It was found that the flasher reduced the drivers’ steering response latencies. This was supposedly the first time to measure drivers’ attention unobtrusively.

Deer-vehicle crashes: extensive peak at 1 hour after sunset

BACKGROUND

On-road encounters with animals resulted in 231 fatalities in the United States in 1999, and the annual number of deer-vehicle crashes (DVCs) has been estimated to total more than 500,000. Previous studies suggest that the number of DVCs is highest during the hours of dusk and dawn. However, these studies have not adequately taken into account the synchronization of visibility and animal behavior with sunset and sunrise. The goal of this study was to determine the temporal variation in the crash risk, so that this variation could be better taken into account by road users.

METHODS

In Finland, the recorded times for 13,379 crashes with moose and 8191 crashes with white-tailed deer were adjusted to sunset and sunrise according to the location and date of occurrence. In addition, two sample distributions of traffic volume on public roads were adjusted to sunset. The DVC rate was computed as the proportion of number of crashes to traffic volume.

RESULTS

The highest crash peak occurred 1 hour after sunset for both species of deer. The relative risk peaked at 30 times the seasonal daytime level of the crash rate for white-tailed deer in the fall and at over 60 times for moose in the summer.

CONCLUSIONS

Drivers can effectively reduce their risk of DVCs by reducing speed and remaining alert for deer intrusions on the roadway during the most critical time of the day: after sunset.

Fatal traffic accidents among trailer truck drivers and accident causes as viewed by other truck drivers

Causality factors, the responsibility of the driver and driver fatigue-related factors were studied in fatal two-vehicle accidents where a trailer truck driver was involved during the period of 1991-1997 (n = 337). In addition, 251 long-haul truck drivers were surveyed in order to study their views regarding contributing factors in accidents involving trucks and the development of possible countermeasure against driver fatigue. Trailer truck drivers were principally responsible for 16% of all the accidents. Younger driver age and driving during evening hours were significant predictors of being principally responsible. In addition, the probability of being principally responsible for the accident increased by a factor of over three if the driver had a chronic illness. Prolonged driving preceding the accident, accident history or traffic offence history did not have a significant effect. Only 2% of the drivers were estimated to have fallen asleep while driving just prior to the accident, and altogether 4% of the drivers had been tired prior to the accident. Of the drivers 13% had however, been driving over 10 h preceding the accident (which has been criminally punishably in Finland since 1995 under the EC regulation) but no individual factors had a significant effect in predicting prolonged driving. The surveyed views regarding causes of truck accidents correspond well with the accident analysis. Accidents were viewed as being most often caused by other road users and driver fatigue was viewed to be no more than the fifth (out of eight) common cause of accidents. The probability of viewing fatigue as a more common cause increased significantly if the driver had experienced fatigue-related problems while driving. However, nearly half of the surveyed truck drivers expressed a negative view towards developing a technological countermeasure against driver fatigue. The negative view was not related to personal experiences of fatigue-related problems while driving.

Sleepiness at work among commercial truck drivers

Two separate groups consisting of both long-haul (N=184) and short-haul (N=133) truck drivers were surveyed to examine the frequency of driver sleepiness-related problems at work during the previous three months and to assess the incidence of sleep apnea syndrome symptoms. We also aimed to identify factors likely to predict self-reported difficulties in staying alert in work driving, dozing off (sometimes referred to as microsleeps) at the wheel and near misses. The responses suggest that for approximately 13% of the long-haul drivers the mean driving time per shift exceeded the EEC regulation. About 40% of the long-haul drivers and 21% of the short-haul drivers reported having problems in staying alert on at least 20% of their drives. Over 20% of the long-haul drivers also reported having dozed off at least twice while driving. Near misses due to dozing off had occurred in 17% of these drivers. Factors indicating sleep apnea syndrome occurred in only about 4% of the long-haul drivers and in only two short-haul drivers. Work and individual related factors as well as factors indicating sleep apnea syndrome contributed only slightly to predicting driver sleepiness-related problems. This suggests that driver sleepiness-related problems tend to be shared by many of the professional drivers, rather than being a "specific" and permanent problem for a smaller portion of drivers. However, difficulties in sleep patterns, such as having difficulty falling asleep, were infrequent.

Cognitive load and detection thresholds in car following situations: safety implications for using mobile (cellular) telephones while driving

This study was aimed at investigating drivers' ability to detect a car ahead decelerating, while doing mobile phone related tasks. Nineteen participants aged between 20 and 29 years, (2000-125000 km driving experience) drove at 80 km/h, 50 m behind a lead car, on a 30 km section of motorway in normal traffic. During each trial the lead car started to decelerate at an average of 0.47 m/s2 while the participant either looked at the car in front (control), continuously dialed series of three random integers on a numeric keypad (divided visual attention), or performed a memory and addition task (non-visual attention). The results indicated that drivers' detection ability was impaired by about 0.5 s in terms of brake reaction time and almost 1 s in terms of time-to-collision, when they were doing the non-visual task whilst driving. This impairment was similar to when the drivers were dividing their visual attention between the road ahead and dialing numbers on the keypad. It was concluded that neither a hands-free option nor a voice controlled interface removes the safety problems associated with the use of mobile phones in a car.

Blink duration as an indicator of driver sleepiness in professional bus drivers

This study focused on eyeblink duration as a measure of sleepiness in on-road driving and on the driving performance of professional bus drivers with polysomnographically confirmed mild obstructive Sleep Apnea Syndrome (OSAS). Ten bus drivers with OSAS and their matched controls participated in the study. The Maintenance of Wakefulness Test (MWT) and a monotonous on-road driving task were completed. Eyeblink duration and frequency and speed control were measured while driving. Lane-keeping was evaluated by the supervisor in the car. Subsequent to these tasks, drivers with OSAS received continuous positive airway pressure treatment (nasal CPAP). After nine weeks of treatment, the tasks were repeated. Prior to treatment the average blink duration in the driving task was significantly longer and sleep latency in the MWT was significantly shorter for bus drivers with OSAS than for controls (mean blink duration 82.3 ms; 51.9 ms and mean sleep latency 23.2 min; 35.4 min), indicating increased daytime sleepiness. Subsequent to treatment both measures in drivers with OSAS decreased to the level of the controls. Treatment effects in MWT and blink duration in on-road driving also correlated significantly. No significant differences between the groups appeared in average blink frequency or driving performance in terms of maintenance of speed. No significant lane drifting appeared either. These results support earlier findings on blink duration as an indicator of increased sleepiness and have important implications for those involved in the transport technological industry. The findings also suggest that nasal CPAP treatment is effective in reducing excessive daytime sleepiness.

Task effects on fatigue symptoms in overnight driving

This study examined the effects of task and time-on-task on fatigue symptoms in overnight driving. Four participants drove an instrumented car 1200 km overnight and completed the same trip as passengers on another night. Subjective ratings of drowsiness, eye blink frequency and duration, microsleeps, and steering-wheel inputs were analysed as a function of time-on-task, and for separate samples when meeting oncoming heavy vehicles. Four video cameras were used to monitor the road view and the face of both the driver and passenger. In terms of eye closure duration, the reported microsleeps were shorter while driving (mean = 0.7 s, SD = 0.2 s) than as a passenger (mean = 2.6 s, SD = 2.0 s). Blink frequency increased with time-on-task as expected, indicating tiredness, and decreased when approaching an oncoming heavy vehicle, indicating attentive response to a potential critical situation. No consistent effect of time-on-task on high-frequency steering-wheel inputs when meeting oncoming heavy vehicles was found. The results raise the important question of what makes a driver wake from a microsleep earlier than a passenger and, given proper monitoring of long eyelid closures, what the proper intervention should be.

Clinical evaluation of the driving ability in stroke patients

OBJECTIVES

Stroke often causes physical, cognitive and psychomotor dysfunction, which markedly decreases the driving ability of stroke patients. The aim of this study was to evaluate the driving ability of stroke patients using multidisciplinary clinical evaluation and driving-related laboratory tests.

MATERIALS AND METHODS

A neurologist evaluated the driving ability of 20 male stroke patients on the basis of his own clinical examination and the observations and measurements of a neurological multidisciplinary rehabilitation team. After that a traffic psychologist evaluated the patients' driving ability on the basis of the driving-related cognitive and psychomotor laboratory tests. The patients themselves also evaluated their driving ability, as did their spouses. All the evaluations were carried out independently using the same 10-point scale. The control group consisted of 20 healthy males, matched by age and driving experience, who went through the same laboratory test package as the patients did.

RESULTS

The stroke patients had more deficiencies in all tested driving related cognitive and psychomotor functions than the controls. The neurologist and the psychologist together evaluated 12 (60%) of the 20 stroke patients being unable to drive; 8 patients out of 11 with non-dominant hemisphere lesion and 4 in the dominant group. The patients themselves and their spouses had a clear tendency to overestimate driving ability compared to the estimates of the neurologist and the psychologist. The hit-rate of the evaluations of the neurologist and traffic psychologist (75%) was high.

CONCLUSION

Stroke patients form a risk group as drivers due to their decreased cognitive and psychomotor abilities, and driving ability should always be evaluated after stroke. The results suggest that multidisciplinary neurological teams are able to evaluate the driving ability of stroke patients reliably. A careful evaluation of driving ability without a driving test requires assessment of cognitive and psychomotor functions critical in driving, which is not feasible for physicians without the support of a multidisciplinary team and/or traffic-related laboratory tests.

Attention and expectation problems in bicycle-car collisions: an in-depth study

One hundred and eighty-eight bicycle-car accidents in four cities were studied by multidisciplinary in-depth analysis. The sample was representative of the national accident statistics. All the accidents were analyzed in detail to reconstruct the actual movements of those involved and to assess detection of the other party. In 37% of collisions, neither driver nor cyclist realized the danger or had time to yield. In the remaining collisions, the driver (27%), the cyclist (24%) or both (12%) did something to avert the accident. Two common mechanisms underlying the accidents were identified. First, allocation of attention such that others were not detected, and second, unjustified expectations about the behavior of others. These mechanisms were found to be closely related to the system of two-way cycle tracks and to the fact that the general priority rule is applied to the crossings of a cycle track and a roadway. The most frequent accident type among collisions between cyclists and cars at bicycle crossings was a driver turning right and a bicycle coming from the driver's right along a cycle track. The result confirmed an earlier finding (Accident Analysis and Prevention 28, 147-153, 1996) that drivers turning right hit cyclists because they looked left for cars during the critical phase. Only 11% of drivers noticed the cyclist before impact. Cyclists' behavior was in marked contrast to that of drivers. In these cases, 68% of cyclists noticed the driver before the accident, and 92% of those who noticed believed the driver would give way as required by law. Cyclists with a driving license and those who cycled daily through the accident site were involved in different accident types to other cyclists.

Driving experience and perception of the lead car's braking when looking at in-car targets

Perception of the lead car's braking was measured on-road when subjects of various levels of driving experience were looking at a digital display located at the lower part of the windscreen, at the speedometer level, or in the mid-console. The brake lights of the lead car were either working normally or switched off. The results indicated that the detection of the lead car's brake lights, in daylight, is substantially impaired when a following driver is looking at the speedometer area and brake lights do not contribute to detection at all when he/she is looking at a target in the mid-console. Driving experience did not influence performance in detecting a closing headway in peripheral vision, in contrast to improvement in lane-keeping found in an earlier study. It is suggested that such differential ability in using peripheral vision for lane and distance-keeping may mislead experienced drivers when they follow another vehicle and perform certain in-car tasks.

American drivers in Europe: different signing policy may cause safety problems at uncontrolled intersections

European signing policy favours uncontrolled intersections--a trend which is in marked contrast to the U.S.A. policy. European drivers must constantly keep in mind the general rule of priority at cross-roads which requires one to yield to a vehicle coming from the right, if not otherwise indicated. For a European driver, an uncontrolled junction means an obligation to yield to vehicles on the right while for U.S. drivers, adapted to the U.S.A. system with more frequent signing, an intersection unsigned from his direction suggests priority for him, particularly in an urban area. To demonstrate a safety problem which follows, three American subjects, visiting professors without previous experience of driving in Europe, were asked to drive a 1.8 km route six times with an instrumented car in the downtown area of Helsinki. All of them first showed unsafe driving practices at uncontrolled intersections with restricted visibility in comparison to a local control group, but changed their strategy, both in terms of speed control and visual search, after they had been informed of the European rule of crossroad priority. In spite of the same general rule at blind intersections in a similar urban environment, a different signing policy may cause safety problems for American drivers in Europe, and translate into more accidents at non-priority intersections. Varying rules and practices in different jurisdictions call for further efforts in presenting vital information to foreign motorists and striving towards worldwide uniform traffic control.

Decreased driving ability in people with Parkinson's disease

BACKGROUND

Driving is a complex form of activity involving especially cognitive and psychomotor functions. These functions may be impaired by Parkinson's disease. The relation between Parkinson's disease and driving ability is still obscure and clinicians have to make decisions concerning the driving ability of their patients based on insufficient information. Until now no studies have compared different methods for evaluating the driving ability of patients with Parkinson's disease.

METHODS

The driving ability of 20 patients with idiopathic Parkinson's disease and 20 age and sex matched healthy control subjects was evaluated by a neurologist, psychologist, vocational rehabilitation counsellor, and driving instructor using a standard 10 point scale. The patients and controls also evaluated their own driving ability. Cognitive and psychomotor laboratory tests and a structured on road driving test were used for evaluating the subjects' driving ability.

RESULTS

The patients with Parkinson's disease performed worse than the controls both in the laboratory tests and in the driving test. There was a high correlation between the laboratory tests and driving test both in the patient group and in the control group. Disease indices were not associated with the driving test. The neurologist overestimated the ability of patients with Parkinson's disease to drive compared with the driving ability evaluated by the structured on road driving test and with the driving related laboratory tests. Patients themselves were not capable of evaluating their own ability reliably.

CONCLUSION

Driving ability is greatly decreased in patients with even mild to moderate Parkinson's disease. The evaluation of patients' driving ability is very difficult to carry out without psychological and psychomotor tests and/or a driving test.

Neuropsychological Correlates of Duration of Glances at Secondary Tasks While Driving

The aim of this study was to find out the neuropsychological measures correlating with overlong glances at secondary in-car tasks while driving. Fifteen. patients with brain damage (without clear neurological or neuropsychological restriction on driving a car) and 11 healthy participants drove a route of 126 km and performed a series of secondary tasks while driving on a highway in an instrumented compact car. Four videocameras allowed detailed analysis of glances during in-car tasks. Neuropsychological measures focused on executive functions, memory, visuospatial skills, and fine motor skills. Moreover, patients' emotional self-evaluation and relatives' evaluation of patients' competencies were included. The proportion of overlong glances away from the road during in-car tasks was greater among the patients than. the healthy drivers. The long glances of the patients correlated strongly with motor and visuospatial deficits, cognitive inflexibility, emotional symptoms, and relatives' evaluations of patients' impaired sensomotor abilities. The results suggest that the frequency of overlong glances was increased by 2 factors: (a) impaired motor and visuospatial skills that evidently caused difficulties in the manipulation of the equipment of the secondary tasks, and (b) impairments of executive functions that were likely to decrease the ability to control the risks related to long glances at the in-car tasks. The slowing of speed during secondary tasks was on the average rather slight and not significantly more pronounced among patients than control drivers, indicating that patients failed to reduce their speed and thus the risk related to prolonged glances at in-car tasks.

Close-following drivers on two-lane highways

This study was intended first to replicate, on two-lane highways, of the Evans and Wasielewski (Accident Analysis & Prevention 14, 57-64, 1982; 15, 121-136, 1983) results on the connection between close-following driving and traffic offenses and, second, to reveal reasons for close-following. A sample of close-following drivers (N = 157) and control drivers (N = 178) was picked from the flow on two-lane main highways. The driver records of the past 3 years showed retrospectively that the close-followers had accumulated 2.3 times more traffic offenses than had the control drivers and 2.0 times more when mileage was taken into account. The result is in agreement with the Evans and Wasielewski results for multi-lane highways, with the additional check for mileage in these data. However, the effect only occurred in males and was more marked in young males. Close-following females even indicated a tendency of having fewer offenses than their controls when their higher mileage was taken into account. Another sample of close-followers interviewed on the road revealed that hurry or desire to overtake the car ahead was the justification for the close-following in the majority of cases. It was suggested that on two-lane highways close-following substantially stems from overtaking needs and maneuvering connected to higher target speeds. This study partly confirms the connection between close-following and an increased number of offenses in comparisons between drivers. However, the suggested connection between close-following and accident involvement, as based on interindividual comparisons, still remains somewhat open.

Speed and acceleration as measures of driving style in young male drivers

This study investigated different measures of speed and acceleration as indicators of safe driving style. 58 young males drove a 7.1-km test route twice in an instrumented car. Drivers were instructed to drive as they usually do. Driving style was measured by both site-specific measures (speed on a crest and speed and lateral acceleration in a sharp and a gentle curve) and general measures (maximum speed and lateral and longitudinal accelerations over the route). Analysis of variance (accident involvement x mileage) showed that drivers who had had prior accidents drove at higher speed and higher accelerations on a sharp curve than accident-free drivers. Drivers involved with accidents drove at higher maximum speed, left accelerations (at right-hand curves), and Equivalent Vector Acceleration, a mean parameter of accelerations, than accident-free drivers. However, multiple regression analysis indicated that only maximum speed predicted the number of accidents significantly. In conclusion, maximum speed seemed to be a convenient and robust measure of a safe driving style.

What surviving drivers learn from a fatal road accident

The effects of involvement in a fatal accident on surviving drivers' subsequent driving behavior were studied. The quantity (mileage) and quality of driving (offences in driver records) of 245 surviving drivers were compared in three-year periods before and after the accident. A random sample of 253 drivers from the driver register were additionally used as controls. The data showed that about half of the car drivers decreased their driving, with greater reductions being associated with more serious injuries. However, the total number of convictions did not reduce but even showed a tendency to increase in proportion to the amount of driving. The proportion of car drivers with post-crash offences was approximately constant (27-32%) independent of any change in mileage. The data suggest that professional heavy-vehicle drivers incurred fewer convictions during the post-crash period in comparison to car drivers. Thirty-seven surviving drivers were further interviewed on the duration and specificity of the effects. With the exception of three drivers, all said that the fatal accident had affected their driving behavior, but only for a relatively short time. Most commonly, the drivers reported that the effect was limited to those circumstances and situations which led to the accident and did not generalize to safer driving practices. This study suggests that car drivers, if not seriously injured, typically return to their 'normal' driving within a few months, while heavy-vehicle drivers show a tendency towards more cautious behavior after a fatal crash in terms of violations, presumably due to the continuous reinforcement which the latter receive in their work community.

Bicycle accidents and drivers' visual search at left and right turns

The accident data base of the City of Helsinki shows that when drivers cross a cycle path as they enter a non-signalized intersection, the clearly dominant type of car-cycle crashes is that in which a cyclist comes from the right and the driver is turning right, in marked contrast to the cases with drivers turning left (Pasanen 1992; City of Helsinki, Traffic Planning Department, Report L4). This study first tested an explanation that drivers turning right simply focus their attention on the cars coming from the left-those coming from the right posing no threat to them-and fail to see the cyclist from the right early enough. Drivers' scanning behavior was studied at two T-intersections. Two well-hidden video cameras were used, one to measure the head movements of the approaching drivers and the other one to measure speed and distance from the cycle crossroad. The results supported the hypothesis: the drivers turning right scanned the right leg of the T-intersection less frequently and later than those turning left. Thus, it appears that drivers develop a visual scanning strategy which concentrates on detection of more frequent and major dangers but ignores and may even mask visual information on less frequent dangers. The second part of the study evaluated different countermeasures, including speed humps, in terms of drivers' visual search behavior. The results suggested that speed-reducing countermeasures changed drivers' visual search patterns in favor of the cyclists coming from the right, presumably at least in part due to the fact that drivers were simply provided with more time to focus on each direction.

Fatal accidents among car and truck drivers: effects of fatigue, age, and alcohol consumption

Fatigue increases the risk of an accident if the driver, on recognizing symptoms of fatigue, does not stop driving. We studied whether a tendency to continue the current activity and complete the task especially affects younger drivers, who are more susceptible to motivational pressures at the wheel in general. The data consisted of Finnish in-depth studies on 586 single-vehicle and 1357 multiple-vehicle accidents in which at least one vehicle occupant died. When excluding alcohol-related cases, the results showed that, first, trailer-truck drivers who either fell asleep or were tired to a degree that contributed to the accident were younger than those involved in the other fatalities. For car drivers, the proportion of fatigue-related cases was approximately constant in each age group, but a variation was seen when studied according to the time of day of the accident, mainly resulting from two distinct peaks. The first was in young drivers 18 to 20 years old between midnight and 6:00 a.m. The other occurred in drivers 56 years and older during the late afternoon hours. These data also indicate that in terms of fatal accidents, fatigue and alcohol seem to be less of a problem for truckers than for car drivers.

Auditory processing in visual brain areas of the early blind: evidence from event-related potentials

Auditory event-related potentials (ERPs) were recorded in early blind subjects and sighted controls when they attended to stimuli delivered to a designated ear under dichotic conditions. The scalp distribution of the processing negativity (PN), the endogenous negativity elicited by attended stimuli, was in the blind posterior to that in the sighted. This suggests that posterior brain areas normally involved in vision participate in auditory selective attention in the early blind. Furthermore, occasional higher-frequency tones in the to-be-ignored ear elicited a negativity (presumably the mismatch negativity; MMN) that had a posterior scalp distribution in the blind as compared to controls. This suggests that the posterior brain areas of the blind also participate in processing of auditory stimulus changes occurring outside the focus of attention.

Neural plasticity in processing of sound location by the early blind: an event-related potential study

Event-related potentials (ERPs) to a change in the locus of origin of a repetitive sound were studied in early blind human subjects. It was found that the N2b component of the ERP was posteriorly distributed on the scalp to that in the sighted control subjects. This suggests that the blind might use, to a larger extent than the sighted, parietal, or perhaps even occipital, brain areas in sound localization. The present results thus appear to demonstrate plastic changes in neural populations involved in processing of auditory space following early loss of vision.

How do accidents happen: a deadline-type experiment on maintaining safety margins

The results of 5 subjects in a deadline-type laboratory task, simulating a hazardous activity with a trade-off between safety and efficiency, showed two basic categories of accident potential. The first one stems from the very normal behavior in which the subjects maintain too small margins of safety and incur an accident in the case of certain coincidences. The second is based on major errors in decision-making or performance resulting in deviant behavior which either is a sufficient cause of an accident or much increases the probability of an accident when the system does not provide sufficient margins of safety.

Drivers' steering behavior when meeting another car: the case of perceptual tropism revisited

It was reported in a recent paper that, when meeting another car, drivers start turning the steering wheel left 2 s before the meeting, indicating, according to the authors explanation, approaching behavior due to the perceptual significance of the oncoming car. The current study was conducted to test an alternative correction-maneuver explanation. The lateral position of passing cars was recorded at several measurement points on two-lane roads, and the mean value was plotted as a function of the time from the meeting instant. The previous data on the steering-wheel angle and the current position data were compared, first on narrow and wide roads and second in car-following and open-road driving condition. Each case involving a more pronounced steering-wheel shift to the left was found to be accompanied by a more pronounced, or sharper, lateral displacement to the right, supporting the correction-maneuver explanation.