At-fault Crashes Research Articles

Warfarin: almost 60 years old and still causing problems

Warfarin: almost 60 years old and still causing problems

Promoting Rehabilitation of Safe Driving Abilities Through Computer-based Clinical and Personal Screening Techniques

The rationale and empirical evidence supporting the development of a computer-based tool for screening the functional abilities shown to be the strongest predictors of at-fault crashes among older drivers are presented in this article. Clinical and home-based applications of the screening tool (the DrivingHealth Inventory and AAA Roadwise Review) are described, with a discussion of its strengths and limitations in each context. The underlying premise throughout is that an integral role for functional screening, leading up to and during an older individual's participation in driving skills rehabilitation programs, may be anticipated as the demand for such services increases in the years ahead.

Crash involvement of drivers with multiple crashes

A goal for any licensing agency is the ability to identify high-risk drivers. Kentucky data show that a significant number of drivers are repeatedly involved in crashes. The objective of this study is the development of a crash prediction model that can be used to estimate the likelihood of a driver being at fault for a near future crash occurrence. Multiple logistic regression techniques were employed using the available data for the Kentucky licensed drivers. This study considers as crash predictors the driver's total number of previous crashes, citations accumulated, the time gap between the latest two crashes, crash type, and demographic factors. The driver's total number of previous crashes was further disaggregated into the drivers’ total number of previous at-fault and not-at-fault crashes. The model can be used to correctly classify at-fault drivers up to 74.56% with an overall efficiency of 63.34%. The total number of previous at-fault crash involvements, and having previous driver license suspensions and traffic school referrals are strongly associated with a driver being responsible for a subsequent crash. In addition, a driver's likelihood to be at fault in a crash is higher for very young or very old, males, drivers with both speeding and non-speeding citations, and drivers that had a recent crash involvement. Thus, the model presented here enables agencies to more actively monitor the likelihood of a driver to be at fault in a crash.

Is Glaucoma Associated with Motor Vehicle Collision Involvement and Driving Avoidance?

To evaluate the association between the diagnosis of glaucoma and motor vehicle collision (MVC) involvement and driving avoidance in drivers aged > or =50 years. Two groups of patients, one with glaucoma and one without, were identified in three university-affiliated eye care practices. Demographic, clinical, and driving characteristics were obtained by chart abstractions and a patient survey. Information regarding MVC involvement was obtained from police records. Patients with glaucoma were less likely (relative risk [RR], 0.67; 95% confidence interval [CI], 0.47-0.97) to be involved in collisions than patients without glaucoma. There was no difference between the at-fault crash rates of the patients with glaucoma and those without (RR, 1.22; 95% CI, 0.67-2.22). Patients with glaucoma had significantly higher levels of avoidance for driving at night (odds ratio [OR], 2.06; 95% CI, 1.11-3.82), driving in fog (OR, 3.80; 95% CI, 1.93-7.48), driving in the rain (OR, 2.99; 95% CI, 1.32-6.76), driving during rush hour (OR, 2.24; 95% CI, 1.16-4.34), driving on the highway (OR, 2.81; 95% CI, 1.19-6.64), and high density driving (OR, 2.88; 95% CI, 1.28-6.46). These associations were adjusted for demographic and medical characteristics as well as visual acuity. Older persons with glaucoma drive at least as safely as, if not more safely than, older persons without glaucoma.

Collision and Violation Involvement of Drivers Who Use Cellular Telephones

The study sample consisted of 3,869 drivers, split approximately 50/50 between observed cell phone users and those observed not using cell phones (labeled "nonusers"). Cell phone use was determined by a snapshot observation made on city streets. The sample represented 54% of those originally observed, for whom a match was obtained for both vehicle license plate and for gender and estimated age group of the observed driver and that of the driver named in the vehicle policy. Data were obtained from records of insurance claims, police-reported collisions and violations, following a strict protocol to protect individual privacy. The dependent measures were at-fault crash claims and "inattention" violations. A logistic regression model controlled for age, gender, exposure (represented by not-at-fault crash claims), alcohol-related offenses, and aggressive driving offenses. The study also involved a comparison of the contributing factors and collision configurations of police-reported collisions involving the users and "nonusers" in the sample. Drivers observed using cell phones had a higher risk of an at-fault crash than did the "nonusers," although the difference was not significant for males. There was no apparent effect on "inattention" violations. The cell phone users also had a higher proportion of rear-end collisions. The violation pattern of cell phone users suggests that they are, in general, riskier drivers. These differences likely reflect lifestyle, attitude and personality factors. It is essential to control for these factors in assessing the direct risk attributable to cellular telephone use.

Traffic crash involvement: experiential driving knowledge and stressful contextual antecedents.

Researchers have rarely examined stressful environments and psychological characteristics as predictors of driving behavior in the same study. The authors hypothesized that (a) safer drivers more accurately assess physical and emotional traffic hazards and (b) stress and emotional states elevate crash risk. The hypotheses were evaluated with procedural and declarative tacit driving knowledge tests requiring assessment of emotional and contextual hazards and with accident reports describing crash antecedents, including stressful events and environmental conditions. Analyses identified separate driving knowledge factors corresponding to emotional and contextual hazards that were significantly related to the crash criteria. Accident report analyses show that stress significantly elevates at-fault crash risk. The results demonstrate the importance of experiential knowledge acquired without instruction (procedural or tacit knowledge) and provide safety recommendations.

MaryPODS revisited: Updated crash analysis and implications for screening program implementation

Problem: Due to the relative scarcity of crashes, there has consistently been a problem with analyses that use crashes as a criterion measure in their analyses. Method: Previous analyses of the relationships between functional capacity measures and at-fault crash involvement for older drivers as reported in the NHTSA Model Driver Screening and Evaluation Program Final Technical Report have been updated to include one additional year of driving experience. Eighteen new at-fault crashes involving drivers who previously had no crash involvement were recorded for the Maryland Motor Vehicle Administration (MVA) test sample during this interval. The method of odds ratio (OR) calculation was used to examine the relationships between functional status predictors and the most salient among the safety outcome measures identified in the Maryland research. Peak valid OR values for the prior and current analyses were contrasted, and the stability of candidate pass–fail cut-points for each predictor relative to values identified in the Final Technical Report was examined. Results: Results indicate that the predictive value of functional tests appears to decrease over time, particularly for the perceptual–cognitive measures. Impact on Industry: The impact of these findings on programs and policies is to underscore a need for periodic reevaluation, spaced at the shortest practical intervals but not more than 2 years apart, in order for functional capacity screening to be applied effectively by licensing authorities, health care professionals, and others to reduce personal risk and enhance public safety.

Visual impairment and driving restrictions. Wick JP, Vernon DD. Dig J Ophthalmol 2002;8:1. (http://www.djo.harvard.edu/meei/OA/Wick/index.html)

The authors sought to determine the adverse incident rates of visually impaired drivers at specific levels of driving restriction and to compare these rates to unimpaired, unrestricted drivers. Visually impaired drivers were identified from statewide databases containing over 1.7 million individuals. Probabilistic linkage methodology was used to link databases containing information on drivers’ licenses, medical conditions, citations and crashes. Exposed drivers with visual impairment (n = 1,527) were compared to an unrestricted, unimpaired cohort (n = 2,939) at three levels of driving restriction and visual impairment (low, moderate, high) for rates of citations, crashes, and at-fault crashes. Exposed drivers were case matched to unexposed cohorts based on age, gender, and geographic location, and the degree of driving restrictions included limitations on speed, area, or time of day. The outcomes were expressed as odds ratio for each of three levels of restriction. When compared to the unimpaired, unrestricted drivers, visually impaired drivers demonstrated a significantly increased number of citations for two of the three levels of driving restriction; significantly increased number of crashes for two of the three levels of driving restriction; and a significantly increased number of at-fault crashes for two of the three levels of driving restriction. The highest odds ratios were associated with the most impaired and most restricted drivers. The authors conclude that visually impaired, restricted drivers are still involved in more motor vehicle crashes and citations than unimpaired, unrestricted drivers, but this increase is modest for drivers with moderate visual impairment and restriction. However, the higher rate of adverse incidents in the most impaired subjects with the most restrictions warrants further investigation.—Thomas J. Liesegang

Evaluating the crash and citation rates of Utah drivers licensed with medical conditions, 1992–1996

Background: Medical problems may affect the ability to drive motor vehicles, and programs that control the issuing of driver licenses to individuals with medical conditions exist in most states. The main activity of these programs is the imposition of restrictions upon the driving privileges of individuals with medical conditions that are deemed to pose some risk to public safety. However, little is known about the effectiveness of these licensing programs. Objective: The objective of this study was to compare the rates of adverse driving events (crash, at-fault crash and citations) experienced by drivers licensed with medical conditions to those of age-, sex- and location-matched controls. Separate comparisons were made for drivers reporting medical conditions licensed with full driving privileges, and those with restricted driving privileges (e.g. speed, area and time of day). Design: Retrospective case-control. Methods: The study population was all drivers licensed in the state of Utah who reported a medical condition on their driver license application, over the 5-year period 1992–1996. Drivers enter the program by self-reporting their medical problems. Control drivers were chosen from the entire population of drivers licensed in Utah for the same period. Information on driver license status, participation in the medical conditions program, citations, involvement in crashes, and death certificate data was obtained from the relevant state agencies. Probabilistic linkage methodology was used to link the records in these disparate databases for eventual analysis. Rates of citation, crashes and at-fault crashes, expressed as events per 10 000 license days, were calculated separately for program drivers and their corresponding control groups for each medical condition category and restriction status. These data were used to determine an estimate of relative risk (RR) and 95% confidence intervals. Results: As a group, medical conditions drivers had modestly elevated rates of adverse driving events compared with control drivers (RR 1.09–1.74). Rates in the largest medical category, ‘cardiovascular conditions’, were not higher than controls. Rates were higher than control for some conditions, such as ‘alcohol’ and ‘learning and memory’, for some adverse events (RR 2.2–5.75). Drivers with more than one medical condition appeared comparable to the general group of medical conditions program drivers. Conclusions: Drivers in Utah medical conditions program had modestly elevated rates of adverse driving events compared to matched controls. Possible underreporting of medical conditions and accurate assessment of exposure rates are potential weaknesses in the program.

Mobility impairments in crash-involved older drivers.

To evaluate potential associations of impairments in physical function with motor vehicle crash involvement in older drivers. Case participants were randomly selected residents of Mobile County, Alabama, greater or less than 65 years old who had sustained an at-fault motor vehicle crash in 1996. Similarly selected crash-free controls were frequency matched to cases on gender and age. Self-report data on demographic variables, medical conditions, medications, driving exposure, and function were collected by telephone interviewers. Relative to crash-free subjects, crash-involved drivers were significantly more likely to report difficulty walking one fourth mile and moving outdoors. Marginally significant associations were observed for trouble carrying a heavy object 100 yards and for the occurrence of falls in the prior year. Increasing numbers of functional limitations were directly related to the odds of crash involvement. In comparison to crash-free controls, crash-involved older drivers are more likely to report other mobility-related impairments, possibly including falls.

Visual risk factors for crash involvement in older drivers with cataract.

The Impact of Cataracts on Mobility project has previously demonstrated that older drivers with cataract have an elevated risk of motor vehicle collision. To examine what types of visual impairment serve as a basis of the increased crash risk of older drivers with cataract. A cross-sectional analysis was performed on 274 older drivers with cataract and 103 older drivers free of cataract recruited through 12 eye care clinics for the purposes of the Impact of Cataracts on Mobility project, a prospective study on driving mobility in older adults with cataract. Tests measured visual acuity, contrast sensitivity, and disability glare for each eye separately using habitual distance correction. The dependent variable was involvement in at least 1 state-recorded, at-fault vehicle crash during the 5 years prior to study enrollment. Logistic regression evaluated associations (odds ratios [ORs]) between visual function and crash involvement. Better and worse eye models defined on the basis of visual acuity were developed. Associations between each type of visual function and crash involvement were adjusted for age, sex, driving exposure, cognitive status, and other types of visual function. For both the better and worse eye models, contrast sensitivity was independently associated with crash involvement, whereas visual acuity and disability glare were not. Drivers with a history of crash involvement were 8 times more likely to have a serious contrast sensitivity deficit in the worse eye (defined as a Pelli-Robson score of 1.25 or less) than those who were crash-free (OR = 7.86; 95% confidence interval [CI], 1.55-39.79); this association was weaker for the better eye but still statistically significant (OR = 3.78; 95% CI, 1.15-12.48). Crash-involved drivers were 6 times more likely to have severe contrast sensitivity impairment in both eyes (OR = 5.78; 95% CI, 1.87-17.86) than crash-free drivers. A severe contrast sensitivity deficit in only 1 eye was still significantly associated with crash involvement (OR = 2.70; 95% CI, 1.16-6.51). Severe contrast sensitivity impairment due to cataract elevates at-fault crash risk among older drivers, even when present in only 1 eye.

Long‐Term Follow‐Up of a High School Alcohol Misuse Prevention Program's Effect on Students' Subsequent Driving

Alcohol-related injuries, particularly motor vehicle, are an important cause of adolescent mortality. School-based alcohol prevention programs have not been evaluated in terms of driving outcomes. This study examined the effects on subsequent driving of a high school-based alcohol prevention program. The Alcohol Misuse Prevention Study included a randomized test of the effectiveness of an alcohol misuse prevention curriculum conducted among 4,635 10th-grade students. Students were assigned to intervention (n = 1,820) or control (n = 2,815) groups and were followed for an average of 7.6 years after licensure, which typically occurred during or shortly after 10th grade. Outcomes examined included alcohol-related and other serious offenses, and at-fault, single-vehicle, and alcohol-related crashes. Only serious offenses (which included alcohol-related) had a significant treatment effect (statistically marginal) after we adjusted for sex, age, race, alcohol use/misuse, family structure, presence of prelicense offenses, age of driver licensure, and parental attitudes toward teen drinking. The effect was found only during the first year of licensure (estimated adjusted relative risk = 0.80, confidence interval = 0.63-1.01). Two first-year serious offense interactions were found. The positive effect was strongest among the largest subgroup of students, those who were drinking less than one drink per week on average before the curriculum, compared with those who drank more than one drink per week (p = 0.009). The effect was also stronger for the small subgroup of students whose parents had not expressed disapproval of teens' drinking, compared with those whose parents had disapproved (p = 0.004). These findings suggest that a high school-based alcohol prevention program can positively affect subsequent driving, particularly that of students who do not use alcohol regularly. The results highlight the need to start prevention efforts early and extend them beyond the initial exposure to driving. Programs should incorporate the differing backgrounds of the students.

Predicting Offenses and Crashes from Young Drivers' Offense and Crash Histories

Previous research has indicated that offenses are better predictors of subsequent crashes than crashes themselves. We examined this hypothesis for 13,800 young beginning drivers in Michigan for up to nine years during the initial years of driving. Our analyses indicated that previous-year offenses are better predictors of both subsequent-year offenses and crashes than either previous-year crashes or at-fault crashes. This finding also held for the apparently higher-risk subset of subsequent-year serious offenses and at-fault crashes. Although there were no gender differences in the predictive power of crashes, it was found that the predictive power of previous offenses to subsequent serious offenses was significantly stronger for women than for men. The predictive power of incidents appeared to increase somewhat with increasing driving experience, suggesting that early incidents may be more attributable to inexperience, a characteristic of all beginning drivers, while later incidents may be more attributable to individual differences.

Persistence of Violation and Crash Behavior Over Time

This analysis examines the ability of previous offenses to predict future high-risk offenses, and similarly, the ability of crashes to predict future high-risk crashes, using the complete driver history data (up to 9 years) for a set of young Michigan subjects. As expected, those with previous ticketed offenses or reported crashes are at greater risk for future offenses or crashes; with a previous-year serious offense doubling the odds of serious offenses during the subsequent year, and a previous-year at-fault crash increasing the odds of subsequent-year at-fault crashes by nearly 50%. There is modest evidence that serious offenses and at-fault crashes may better predict subsequent behavior in females and in more experienced drivers. This latter finding is also evidenced by the fact that records of these young drivers are less predictive of subsequent driving history than is true for records of all drivers in general found in other studies. This suggests that, in the early stages of driving, offenses and crashes are, at least in part, attributable to inexperience, and hence, characteristic of all beginning drivers.

Changes in young adult offense and crash patterns over time

A study of 13 809 young adult drivers in Michigan examined offenses and crashes (‘incidents’) for an average of 7 years after their original license date. During this period, 73% of subjects committed an offense that resulted in a conviction and 58% had a crash that was reported to the police. Forty-two percent had committed an offense classified as ‘serious,’ and 21% had an ‘at-fault’ crash. The odds of an offense being serious decreased approximately 8% per year of licensure, independent of gender or age at licensure. Similarly, the odds of a crash being at-fault decreased overall about 6% per year of licensure, but the decline was more than twice as fast for women as for men. Examining the empirical rates directly, it was found that the rate for minor offenses increased somewhat with time and then stabilized, while the rate for serious offenses declined. Also, offenses were less likely to be serious the later they occurred in the sequence of offenses for an individual. For crashes, the risk of having an at-fault crash declined more rapidly than the risk of a not-at-fault crash, although the rate of decrease began to equalize after approximately 5 years of licensure. The proportion of crashes that were at-fault did not decline over the sequence of crashes for an individual. Although crashes and offenses are positively correlated, they follow different trajectories over the early years of licensure.

Relations among chronic medical conditions, medications, and automobile crashes in the elderly: a population-based case-control study.

Older drivers have elevated crash rates and are more likely to be injured or die if they have a crash. Medical conditions and medications have been hypothesized as determinants of crash involvement. This population-based case-control study sought to identify medical conditions and medications associated with risk of at-fault crashes among older drivers. A total of 901 drivers aged 65 years and older were selected in 1996 from Alabama Department of Public Safety driving records: 244 at-fault drivers involved in crashes; 182 not at-fault drivers involved in crashes; and 475 drivers not involved in crashes were enrolled. Information on demographic factors, chronic medical conditions, medications, driving habits, visual function, and cognitive status was collected. Older drivers with heart disease (odds ratio (OR) = 1.5, 95% confidence interval (CI): 1.0, 2.2) or stroke (OR = 1.9, 95% CI: 0.9, 3.9) were more likely to be involved in at-fault automobile crashes. Arthritis was also associated with an increased risk among females (OR =1.8, 95% CI: 1.1, 2.9). Use of nonsteroidal antiinflammatory drugs (OR = 1.7, 95% CI 1.0, 2.6), angiotensin converting enzyme inhibitors (OR = 1.6, 95 CI: 1.0, 2.7), and anticoagulants (OR = 2.6, 95% CI: 1.0, 73) was associated with an increased risk of at-fault involvement in crashes. Benzodiazepine use (OR = 5.2, 95% CI: 0.9, 30.0) was also associated with an increased risk. Calcium channel blockers (OR = 0.5, 95% CI: 0.2, 0.9) and vasodilators (OR = 0.3, 95% CI: 0.1, 1.0) were associated with a reduced risk of crash involvement. The identification of medical conditions and medications associated with risk of crashes is important for enhancing the safety and mobility of older drivers.

Characteristics of motor vehicle crashes of drivers with dementia of the Alzheimer type.

To determine whether there is a difference in crash rates and characteristics between drivers with dementia of the Alzheimer type (DAT) and nondemented older persons who were controls. A pilot study using a 5-year retrospective analysis of state-recorded crash data and crash characteristics followed by patient enrollment into a study on road test skills. Alzheimer's Disease Research Center at Washington University in St. Louis, Missouri. Subjects were enrolled as volunteers in a longitudinal study of aging and DAT. One hundred twenty-one subjects (58 nondemented, older drivers and 63 drivers with DAT) with a mean age of 77 years met the inclusion criteria for this study. DAT was diagnosed using validated clinical diagnostic criteria and was staged by the Clinical Dementia Rating (CDR) Scale. All subjects with DAT were in the very mild (CDR = 0.5) or mild (CDR = 1) stages. State-recorded traffic crashes. Also, a daily driving diary was completed by each subject and used to estimate miles traveled per year. Subjects diagnosed with mild DAT (CDR = 1) reported less roadway exposure (average number of miles driven per year) than did drivers with very mild DAT (CDR = 0.5) or controls. Crashes in both groups were infrequent, with 0.07 state-recorded crashes per driver per year in the nondemented group (CDR = 0), 0.06 in the very mild DAT group (CDR = 0.5), and 0.04 in the mild DAT group (CDR = 1). There was no statistical difference in the crash frequency between groups, even when adjusting for exposure. Drivers with DAT had trends toward more at-fault crashes, crashes with injuries, and crashes in which the officer on the scene cited failure to yield. In our sample, individuals with very mild or mild DAT who continued to drive seemed to have crash rates similar to those of the controls. There may be significant differences between the causes and the consequences of crashes involving drivers with DAT when compared with cognitively intact age-matched controls, but none were found in this pilot study. Further research on crash characteristics is needed in larger samples of community-based drivers with DAT across wider ranges of dementia severity to address issues such as driving competency and public safety.

Diabetes and automobile crashes in the elderly. A population-based case-control study.

The aim of this study was to estimate the association between diabetes and its complications and at-fault automobile crashes among older drivers. This was a population-based case-control study. Case subjects were drivers aged > or = 65 years who had been involved in a crash during 1996 in which they were at fault. Two control groups were selected: 1) crash-involved not-at-fault subjects and 2) non-crash-involved subjects. Telephone interviewers collected information on demographic characteristics, driving habits, diabetes sequelae and treatment, other chronic medical conditions, and visual function. Overall, there was no association between diabetes and at-fault crash involvement. The adjusted odds ratio (OR) for diabetes was 1.1 (CI 0.7-1.9) when case subjects were compared with either control group. However, the adjusted OR for diabetes was 2.5 (0.9-7.2) among subjects who had been involved in a crash in the 4 years preceding 1996, while it was only 0.9 (0.5-1.7) among those who had not. There was no evidence of an association between treatment modalities and at-fault crash involvement. Case subjects were, although not significantly (P = 0.25), more likely (OR 2.4) to report neuropathy compared with both control groups, and retinopathy was not associated with increased crash risk. This study provides no evidence that older drivers with diabetes are at increased risk for automobile crashes. There remains the possibility that those with diabetes who have more severe disease or have had multiple crashes are at increased risk.

A preliminary assessment of the medical and functional factors associated with vehicle crashes by older adults.

To examine associations between medical and functional variables and at-fault car crashes in a cohort of older drivers. A case-control study. A tertiary care medical center. Older drivers (ages 55-90 years) residing in Jefferson County, Alabama (n = 174). Cases were drivers who had at least one at-fault crash in the previous 6 years; controls were crash-free during the same period. Self-reported medical conditions, reported and observed functional measures, and urinary drug screens. The occurrence of one or more at-fault car crashes in the 6 years preceding the 1991 assessment date represented the outcome measure. Ninety-nine older drivers experienced between one and seven at-fault vehicle crashes during the period 1985 through 1991, whereas 75 drivers did not. Logistic regression models indicated that the following variables were independently associated with crash involvement: A 40% or greater reduction in the useful field of view (OR = 6.1; 95% CI, 2.9 to 12.7; P < 0.001), black race (OR = 6.6; 95% CI, 1.7 to 26.2; P = .007), a history of falling in the previous 2 years (OR = 2.6; CI, 1.1 to 6.1; P = .025), and not taking a beta-blocking drug (OR = 4.3; CI, 1.2 to 15.0; P = .023). Functional assessments, such as a comprehensive test of visual processing, a falls history, and a review of current medications may be of greater relevance than specific medical conditions in the identification of older at-risk drivers. If prospective studies determine that falling and crashing share risk factors, a unified approach to the prevention of these mobility disorders could result. The finding of an independent association of black race with at-fault crashing is in need of further clarification because of the low representation of black drivers in this sample.

Driving avoidance and functional impairment in older drivers

The purpose of this study was to examine the association between visual and cognitive impairment in older drivers and their avoidance of potentially challenging driving situations. A group of 257 older drivers participated in assessments of visual sensory function, eye health and cognitive function including the useful field of view test, and completed a structured questionnaire on driving exposure and how frequently they avoided challenging driving situations. Results replicated earlier studies showing that many older drivers limit their exposure to driving situations which are generally believed to be more difficult (e.g. rain, night, heavy traffic, rush hour). Furthermore, older drivers with objectively determined visual and/or attentional impairments reported more avoidance than those free of impairments; those with the most impairment reported avoiding more types of situations than other less impaired or non-impaired drivers. Older drivers with a history of at-fault crashes in the prior five years reported more avoidance than those who had crash-free records. Future research should evaluate the potentially beneficial role of self-regulation in enhancing older driver safety, particularly in those older drivers with visual and attentional processing impairments who have elevated crash risk.