Driver Impairment Research Articles

Diagnostic fusion for in vehicle Driver vigilance assessment

Driver impairment in broad terms is one of the most common causes for traffic accidents. In the context of impairment, decreased vigilance, fatigue and inattention are major factors accounting for driver errors. The real time detection and assessment of driver impairment through non-intrusive driver monitoring system is a real challenge. Within this paper, after an extended state of the art of the existing technologies and systems a Driver vigilance monitoring system, based on the fusion of physiological, behavioural and contextual information is described. This system has been implemented on a vehicle and real conditions experiments have been performed on motorway.

Analysis of Log Hauling Vehicle Accidents in the State of Georgia, USA, 1988–2004

Mechanical failure rates associated with logging vehicle accidents in Georgia are dramatically lower today than they were in 1988–1991 before these trucks became subject to random roadside inspections. Mechanical failure dropped by half for logging tractor-trailers (from 10.9% to 4.8%) and by two-thirds for logging trucks (from 12.9% to 4.2%). Mechanical failure is now the seventh most cited contributing factor in logging tractor-trailer accidents instead of first as it was prior to 1991. Specific types of mechanical failures have also declined sharply. Three potential failure items that are visually checked during roadside inspections - brakes, slick tires, and lights - have seen the most dramatic declines. Brake failure has dropped by two-thirds and improper lights as a factor have almost disappeared. Driver impairment due to use of alcohol or drugs today occurs in less than 0.5 percent of accidents. Factors associated with logging vehicle accidents today in Georgia closely resemble those associated with all trucking accidents generally. Accidents per million tons of wood consumed, however, has increased steadily from 11 in 1991 to 19 per million tons in 2003.

Alcohol and Other Drug Use Among Victims of Motor-Vehicle Crashes—West Virginia, 2004-2005

Alcohol use is a well-established risk factor for motor-vehicle crashes. In 2005, approximately 39% of all traffic fatalities in the United States were alcohol related. Evidence of driver impairment from use of drugs other than alcohol is less definitive. In 2005, an estimated 4.3% of persons in the United States reported driving under the influence of a drug used recreationally during the preceding year, and an unknown percentage drove while impaired by drugs being used for medical reasons. To measure the prevalence of alcohol and drug use among persons killed in motor-vehicle crashes in West Virginia (where test results were available for >80% of fatalities), CDC analyzed 2004 and 2005 data reported by the West Virginia Office of the Chief Medical Examiner (OCME) to the Fatality Analysis Reporting System (FARS) of the National Highway Traffic Safety Administration (NHTSA). This report summarizes the results of that analysis, which determined that the prevalence of drug use (25.8%) was similar to the prevalence of a blood alcohol concentration (BAC) >0.08 g/dL (27.7%) among persons killed in motor-vehicle crashes. These results suggest that drug use contributes substantially to driver impairment in West Virginia. Measuring the magnitude of this problem nationally will require better surveillance data. Both surveillance and the development of prevention measures are hampered by difficulties in quantifying and defining drug impairment.

Changing Patterns of Drug and Alcohol Use in Fatally Injured Drivers in Washington State

We have previously reported on patterns of drug and alcohol use in fatally injured drivers in Washington State. Here we revisit that population to examine how drug use patterns have changed in the intervening 9 years. Blood and serum specimens from drivers who died within 4 h of a traffic accident between February 1, 2001, and January 31, 2002, were analyzed for illicit and therapeutic drugs and alcohol. Drugs when present were quantitated. Samples suitable for testing were obtained from 370 fatally injured drivers. Alcohol was detected above 0.01 g/100 mL in 41% of cases. The mean alcohol concentration for those cases was 0.17 g/100 mL (range 0.02-0.39 g/100 mL). Central nervous system (CNS) active drugs were detected in 144 (39%) cases. CNS depressants including carisoprodol, diazepam, hydrocodone, diphenhydramine, amitriptyline, and others were detected in 52 cases (14.1%), cannabinoids were detected in 47 cases (12.7%), CNS stimulants (cocaine and amphetamines) were detected in 36 cases (9.7%), and narcotic analgesics (excluding morphine which is often administered iatrogenically in trauma cases) were detected in 12 cases (3.2%). For those cases which tested positive for alcohol c. 40% had other drugs present which have the potential to cause or contribute to the driver's impairment. Our report also considers the blood drug concentrations in the context of their interpretability with respect to driving impairment. The data reveal that over the past decade, while alcohol use has declined, some drug use, notably methamphetamine, has increased significantly (from 1.89% to 4.86% of fatally injured drivers) between 1992 and 2002. Combined drug and alcohol use is a very significant pattern in this population and is probably overlooked in DUI enforcement programs.

Estimating Time of Last Oral Ingestion of Cannabis From Plasma THC and THCCOOH Concentrations

Estimating the time of last cannabis use is important in assessing possible impairment of drivers involved in accidents, in verifying accuracy of court testimony and in the future, helpful in therapeutic monitoring of cannabis agonists. In 1992, Huestis et al developed model 1, based on plasma Delta-tetrahydrocannabinol (THC) concentrations, and model 2, on plasma 11-nor-9-carboxy-Delta(9)-tetrahydrocannbinol/THC ratios, that predicted 95% confidence intervals for time of last cannabis use. These models seemed to be valuable when applied to the small amount of data from published studies of oral ingestion, a route of administration more popular with the advent of cannabis therapies. A study was designed to further validate the models after oral ingestion of THC, and to determine whether they could predict last usage after multiple oral doses. Eighteen subjects in IRB-approved studies participated after providing informed consent. Each of 12 subjects in one group received a single 10 mg oral dose of dronabinol (synthetic THC). In another protocol, 6 subjects received 4 different oral daily doses, divided into thirds and administered with meals for 5 consecutive days. There was a 10-day washout period between each dosing regimen. Daily doses were 0.39, 0.47, and 14.8 mg THC in hemp oil and 7.5 mg dronabinol. Blood specimens were collected throughout the study and analyzed for plasma THC and 11-nor-9-carboxy-Delta(9)-tetrahydrocannbinol by gas chromatography/mass spectrometry with limits of quantification (LOQs) of 0.5 and 1.0 ng/mL, respectively. Actual times between ingestion of THC and blood collection spanned 0.5 to 16 hours. All plasma specimens with analyte concentrations >LOQ (n=90) were evaluated. Models 1 and 2 correctly predicted time of last THC ingestion for 74.4% and 90.0% of plasma specimens, respectively. 96.7% of predicted times were correct with one overestimate and 2 underestimates using the time interval defined by the lowest and highest 95% confidence limit of both models. These results provide further evidence of the usefulness of the predictive models in estimating the time of last oral THC ingestion after single or multiple doses.

Cognition and motor control as a function of Δ 9-THC concentration in serum and oral fluid: Limits of impairment

Cannabis use has been associated with increased risk of becoming involved in traffic accidents; however, the relation between THC concentration and driver impairment is relatively obscure. The present study was designed to define performance impairment as a function of THC in serum and oral fluid in order to provide a scientific framework to the development of per se limits for driving under the influence of cannabis. Twenty recreational users of cannabis participated in a double-blind, placebo-controlled, three-way cross-over study. Subjects were administered single doses of 0, 250 and 500 μg/kg THC by smoking. Performance tests measuring skills related to driving were conducted at regular intervals between 15 min and 6 h post smoking and included measures of perceptual-motor control (Critical tracking task), motor impulsivity (Stop signal task) and cognitive function (Tower of London). Blood and oral fluid were collected throughout testing. Results showed a strong and linear relation between THC in serum and oral fluid. Linear relations between magnitude of performance impairment and THC in oral fluid and serum, however, were low. A more promising way to define threshold levels of impairment was found by comparing the proportion of observations showing impairment or no impairment as a function of THC concentration. The proportion of observations showing impairment progressively increased as a function of serum THC in every task. Binomial tests showed an initial and significant shift toward impairment in the Critical tracking task for serum THC concentrations between 2 and 5 ng/ml. At concentrations between 5 and 10 ng/ml approximately 75–90% of the observations were indicative of significant impairment in every performance test. At THC concentrations >30 ng/ml the proportion of observations indicative of significant impairment increased to a full 100% in every performance tests. It is concluded that serum THC concentrations between 2 and 5 ng/ml establish the lower and upper range of a THC limit for impairment.

Impaired Performance in Commercial Drivers

Sleepiness plays an important role in major crashes of commercial vehicles. Because determinants are likely to include inadequate sleep and sleep apnea, we evaluated the role of short sleep durations over 1 wk at home and sleep apnea in subjective sleepiness (Epworth Sleepiness Scale), objective sleepiness (reduced sleep latency as determined by the Multiple Sleep Latency Test), and neurobehavioral functioning (lapses in performance, tracking error in Divided Attention Driving Task) in commercial drivers. Studies were conducted in 247 of 551 drivers at higher risk for apnea and in 159 of 778 drivers at lower risk. A multivariate linear association between the sets of outcomes and risk factors was confirmed (p < 0.0001). Increases in subjective sleepiness were associated with shorter sleep durations but not with increases in severity of apnea. Increases in objective sleepiness and performance lapses, as well as poorer lane tracking, were associated with shorter sleep durations. Associations with sleep apnea severity were not as robust and not strictly monotonic. A significant linear association with sleep apnea was demonstrated only for reduced sleep latency. The effects of severe apnea (apnea-hypopnea index, at least 30 episodes/h), which occurred in 4.7%, and of sleep duration less than 5 h/night, which occurred in 13.5%, were similar in terms of their impact on objective sleepiness. Thus, addressing impairment in commercial drivers requires addressing both insufficient sleep and sleep apnea, the former being more common.

Behavioral Effects of Driver Distraction and Alcohol Impairment

There remains some debate regarding secondary task distractions, such as cell phones, as a risk factor in traffic crashes and their relative risk compared to existing factors, such as engagement in common in-vehicle tasks and alcohol impairment. Moreover, studies of driver impairment often investigate single risk factors rather than combined factors (e.g. distraction task while drunk). This study compared non-distracted driving in a motion-based driving simulator to distracted driving (hands-free cell phone conversations, common in-vehicle tasks) either while sober or combined with alcohol (BAC 0.08). The results indicated that during a car following scenario, drivers engaged in the conversations or completing in-vehicle tasks were more impaired than drivers that were not involved in any distraction task. Indeed, both the cell phone and in-vehicle sources of distraction were generally more impairing than intoxication at the legal limit.

Assessment of driver impairment: Evaluation of a two-choice tester using ethanol

Fifteen healthy volunteers aged 18–35 years took part in this three period crossover study evaluating a portable performance tester designed for roadside use. They received by mouth placebo and two doses of ethanol on separate days. Doses were calculated to produce blood alcohol levels of 50 and 80 mg/100 ml. Testing was carried out before the drink and starting at 40 min after the drink. Breathalyser readings showed peak blood alcohol levels of 54.4 mg/100 ml (S.D 11.1) for the smaller dose and 83.0 mg/100 ml (S.D. 8.4) at the larger dose. Significant impairment was seen with the larger dose of ethanol. Response time was increased for the arrow flankers test (attention in the presence of distractors), and errors were increased for paired associates (visuospatial working memory) and for length estimation (judgement). A composite measure showed a clear dose-related pattern of impairment. These results indicate that a short test battery taking about ten minutes to complete can reliably show the effects of ethanol under controlled laboratory conditions. Further work is needed in the field, and with a more varied population to assess the use of such a device to assess impairment due to alcohol and drugs at the roadside.

Workshop: Psychotropic Drugs and Driver Impairment

Atypical neuroleptics like amisulpride and quetiapine as well as newer selective antidepressants have an advantage on driving related psychomotor skills.

Factors Associated with Higher Levels of Injury Severity in Occupants of Motor Vehicles That Were Severely Damaged in Traffic Crashes in Kentucky, 2000-2001

Objectives: The majority of motor vehicle occupants who were killed or hospitalized in crashes in Kentucky in 2000–2001 occupied vehicles that were severely damaged in the crash. Even so, overall only a small percentage of all severely damaged vehicle occupants were killed or hospitalized. The purpose was to identify occupant, vehicle, crash, and roadway/environmental factors that were associated with increased risk of severe injury in crashes where the occupant's vehicle was severely damaged. Methods: This study probabilistically linked Kentucky's statewide motor vehicle crash and inpatient hospital discharge data files for 2000 and 2001, and selected cases representing occupants of vehicles that were reported by police as having either “severe” or “very severe” damage. For occupants who were identified through data linkage as having been hospitalized, the Injury Severity Score (ISS) was calculated using ICDMAP-90 TM software, and the scores were stratified into the following categories: critical (> 24), severe (15–24), moderate (9–14), and mild (< 9). We then created an outcome variable, injury severity level, with five levels: killed; hospitalized with at least moderate injuries (ISS = critical, severe, or moderate); hospitalized with mild injuries (ISS = mild); injured according to the police report but not hospitalized; and no apparent injury according to the police report. We performed a stepwise, ordinal logistic regression of injury severity, using independent variables identified from the existing crash literature. Results: Occupant risk factors for higher levels of injury severity selected by the regression were age (risk increased with age, other factors being equal), female gender, restraint non-use, ejection from the vehicle, and driver impairment (by alcohol and/or drugs). Crash risk factors included head-on collision, collision with a fixed object, vehicle rollover, and vehicle fire. Roadway/environmental factors were federal- or state-maintained roadway and posted speed limit 89 kph (55 mph) or greater. Conclusions: Many of the identified risk factors are explicitly or implicitly mentioned in the strategic plans of key organizations involved in highway safety and injury prevention in Kentucky. Our analysis provides additional evidence of their importance, and confirms that their mitigation will reduce injury severity in crashes involving severe vehicle damage. Additionally, older occupants and female occupants showed increased risks of serious injury, but to our knowledge these factors are not currently addressed in any state plans. An opportunity exists to clarify the nature of these risks through further studies, which might lead to the identification of countermeasures specific to these populations.

Factors Associated with Higher Levels of Injury Severity in Occupants of Motor Vehicles That Were Severely Damaged in Traffic Crashes in Kentucky, 2000-2001

Objectives: The majority of motor vehicle occupants who were killed or hospitalized in crashes in Kentucky in 2000–2001 occupied vehicles that were severely damaged in the crash. Even so, overall only a small percentage of all severely damaged vehicle occupants were killed or hospitalized. The purpose was to identify occupant, vehicle, crash, and roadway/environmental factors that were associated with increased risk of severe injury in crashes where the occupant's vehicle was severely damaged. Methods: This study probabilistically linked Kentucky's statewide motor vehicle crash and inpatient hospital discharge data files for 2000 and 2001, and selected cases representing occupants of vehicles that were reported by police as having either “severe” or “very severe” damage. For occupants who were identified through data linkage as having been hospitalized, the Injury Severity Score (ISS) was calculated using ICDMAP-90 TM software, and the scores were stratified into the following categories: critical (> 24), severe (15–24), moderate (9–14), and mild (< 9). We then created an outcome variable, injury severity level, with five levels: killed; hospitalized with at least moderate injuries (ISS = critical, severe, or moderate); hospitalized with mild injuries (ISS = mild); injured according to the police report but not hospitalized; and no apparent injury according to the police report. We performed a stepwise, ordinal logistic regression of injury severity, using independent variables identified from the existing crash literature. Results: Occupant risk factors for higher levels of injury severity selected by the regression were age (risk increased with age, other factors being equal), female gender, restraint non-use, ejection from the vehicle, and driver impairment (by alcohol and/or drugs). Crash risk factors included head-on collision, collision with a fixed object, vehicle rollover, and vehicle fire. Roadway/environmental factors were federal- or state-maintained roadway and posted speed limit 89 kph (55 mph) or greater. Conclusions: Many of the identified risk factors are explicitly or implicitly mentioned in the strategic plans of key organizations involved in highway safety and injury prevention in Kentucky. Our analysis provides additional evidence of their importance, and confirms that their mitigation will reduce injury severity in crashes involving severe vehicle damage. Additionally, older occupants and female occupants showed increased risks of serious injury, but to our knowledge these factors are not currently addressed in any state plans. An opportunity exists to clarify the nature of these risks through further studies, which might lead to the identification of countermeasures specific to these populations.

Quantifying Car following Performance as a Metric for Primary and Secondary (Distraction) Task Load: Part A — Modification of Task Parameters

Driver impairment as a result of attention-related factors is a common concern to many areas of safety research in driving. Previously, the “coherence technique” was developed to provide several metrics of performance in relation to the continuous task of car following presumed to require vigilance and perceptual capacity (Brookhuis, De Waard, &amp; Mulder, 1994). This study examines a modified version of this technique that is more natural. This modified technique was sensitive to both increased primary and secondary (distraction) task load.

Driver vigilance monitoring - new developments within the awake project

Driver drowsiness is a major cause of traffic crashes all over the world. The real time detection and assessment of driver impairment through non-intrusive driver drowsiness detection system is a real challenge. Within this paper a quick overview of former development related with driver vigilance monitoring system is given. Then latest developments and results concerning sensing capabilities and behavioural diagnostic are presented. Finally some promising results are presented.

Criteria for driver impairment

Most traffic accidents can be attributed to driver impairment, e.g. inattention, fatigue, intoxication, etc. It is now technically feasible to monitor and diagnose driver behaviour with respect to impairment with the aid of a limited number of in-vehicle sensors. However, a valid framework for the evaluation of driver impairment is still lacking. To provide an acceptable definition of driver impairment, a method to assess absolute and relative criteria was proposed to fulfil the paradoxical goal of defining impaired driving which is consistent yet adaptable to interindividual differences.

Hearing Impairment And Hypertension Among Long Distance Bus Drivers

Objectives: To investigate the prevalence of possible hearing impairment and hypertension in long distance bus drivers compared to the city bus drivers in Abha city. Methods: This was a cross-sectional study involving 62 long distance bus drivers and 46 city bus drivers from October 2001 to March 2002. A specially-designed questionnaire was administered to the drivers to explore some of their socioeconomic backgrounds. A pure tone air conduction audiometry and blood pressure measurements were performed. Results: Long distance bus drivers' workload is significantly higher than that of city drivers (total weekly hours 64.0 + 14.3 compared to 46.7 + 5.5). Hearing impairment was significantly more among long distance drivers in the frequencies of 250, 500, 1000 and 2000 Hz especially in the left ear even after age corrections. The prevalence of mild hearing loss and hypertension were also higher among the long distance drivers (19.4% vs 4.5% and 38.7% vs 13% respectively). Conclusion and recommendations: This study showed more hearing affection and a higher prevalence of hypertension among long distance bus drivers than their counterparts operating in the city. Their hearing acuity should be tested before they start work and regularly afterwards. The stresses and strains of the job should be further studied and relieved; and regular health checks including blood pressure monitoring are to be instituted.

Antidepressants and Driver Impairment

The current review summarizes the major results from all published studies from 1983 to 2000 (9 double-blind, crossover, placebo-controlled studies in healthy volunteers and 1 double-blind, baseline-controlled study in patients) that have determined the effects of antidepressants on actual driving performance using a standard test. That test measures driving impairment from vehicular "weaving" (i.e., standard deviation of lateral position [SDLP]) during 1 hour of on-the-road driving in normal traffic. Changes in SDLP after acute doses of sedating antidepressants (i.e., amitriptyline, imipramine, doxepin, and mianserin) were comparable to those seen in drivers conducting the same test with a blood alcohol concentration of 0.8 mg/mL or more. Driving performance of subjects returned to placebo levels after 1 week of treatment, except after treatment with mianserin, for which the impairing effect lasted unabated over treatment. Nocturnal doses of sedating antidepressants (i.e., dothiepin, mianserin, and mirtazapine), however, did not produce residual driving impairment when measured the next day. Nonsedating antidepressants (i.e., moclobemide, fluoxetine, paroxetine, venlafaxine, and nefazodone) generally did not affect SDLP. However, SDLP rose to unacceptable levels after administration of combinations of nonsedating antidepressants and benzodiazepines with incompatible pharmacokinetic profiles. Correlational analyses demonstrated that conventional tests of psychomotor performance or self-ratings of side effects did not strongly predict antidepressant effects on SDLP. Regression analysis revealed a strong linear relation between antidepressant effects in the standard driving test and the number of patients reporting somnolence in clinical trials with the same antidepressants. Application of actual driving tests remains essential to conclusively defining the potential hazard of drugs for driving.

Motor vehicle crashes and violations among drivers with multiple sclerosis

Schultheis MT, Garay E, Millis SR, DeLuca J. Motor vehicle crashes and violations among drivers with multiple sclerosis. Arch Phys Med Rehabil 2002;83:1175-8. Objective: To investigate differences in the incidence of motor vehicle crashes (MVCs) and violations among drivers with multiple sclerosis (MS) when cognitive impairment is present. Design: Archival evaluation of Department of Motor Vehicles (DMV) records. Setting: Medical rehabilitation research organization. Participants: Community-dwelling drivers, 27 subjects with documented MS (14 MS without cognitive impairment [MS−], 13 MS with cognitive impairment [MS+]) and 17 healthy control subjects, matched on age, sex, and driving experience. Interventions: Not applicable. Main Outcome Measures: Incidence of MVCs and motor vehicle violations as documented by DMV reports for the past 5 years. Results: MS+ subjects showed a higher incidence of MVCs when compared with control and MS− subjects. No significant difference in the incidence of motor vehicle violations was observed between groups. Conclusions: The presence of cognitive impairment in drivers with MS can result in an increased risk of MVC involvement. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Task-induced fatigue states and simulated driving performance.

States of fatigue are implicated in driver impairment and motor vehicle accidents. This article reports two studies investigating two possible mechanisms for performance impairment: (1) loss of attentional resources; and (2) active regulation of matching effort to task demands. The first hypothesis predicts that fatigue effects will be accentuated by high task demands, but the second hypothesis predicts that fatigue effects will be strongest in "underload" conditions. In two studies, drivers performed a stimulated driving task, in which task demands were manipulated by varying road curvature. In a "fatigue induction" condition, the early part of the drive was occupied by performance of a demanding secondary task concurrently with driving, after which the concurrent task ceased. Post-induction driving performance was compared with a control condition in which drivers were not exposed to the induction. In both studies, the fatigue induction elicited various subjective fatigue and stress symptoms, and also raised reported workload. Fatigue effects on vehicle control and signal detection were assessed during and after the fatigue induction. The fatigue induction increased heading error, reduced steering activity, and, in the second study, reduced perceptual sensitivity on a secondary detection task. These effects were confined to driving on straight rather than on curved road sections, consistent with the effort regulation hypothesis. The second study showed that fatigue effects were moderated by a motivational manipulation. Results are interpreted within a control model, such that task-induced fatigue may reduce awareness of performance impairment, rather than reluctance or inability to mobilize compensatory effort following detection of impairment.

DRIVER VIGILANCE MONITORING - NEW DEVELOPMENTS

Driver drowsiness is a major cause of traffic crashes all over the world. The real time detection and assessment of driver impairment through non-intrusive driver drowsiness detection system is a real challenge. Within this paper a quick overview of former development related with driver monitoring system is given. Then latest developments and results concerning sensing capabilities and diagnostic are presented. Finally some promising results are presented.