Older drivers do not have a high crash risk--a replication of low mileage bias

The widespread claim that older drivers are overly involved in crashes has apparent support from crash data, especially when distance travelled is used as the exposure measure. However, independent of age, drivers travelling more kilometres will typically have lower crash rates per kilometre than those driving fewer kilometres. This paper uses Dutch travel survey data from a large sample of respondents to confirm previous research findings concerning the association between annual mileages driven and crash involvement. When the crash rates of drivers of different ages were compared after being matched for yearly driving distance, most drivers aged 75 years and above were indicatively safer than all other drivers. Only older drivers travelling less than 3000 km per year (just over 10% of all older drivers in the survey) gave any indication of elevated crash rates.     

Risky driving habits and motor vehicle driver injury

Risky driving is an important cause of motor vehicle injury, but there is a lack of good epidemiological data in this field, particularly data comparing risky driving in younger drivers to those of other age groups. We examined the relationship between risky driving habits, prior traffic convictions and motor vehicle injury using cross-sectional data amongst 21,893 individuals in New Zealand, including 8029 who were aged 16-24 years. Those who reported frequently racing a motor vehicle for excitement or driving at 20 km/h or more over the speed limit, and those who had received traffic convictions over the past 12 months, were between two and four times more likely to have been injured while driving over the same time period. Driving unlicensed was a risk factor for older but not younger drivers, and driving at 20 km/h or more above the speed limits was a stronger risk factor for younger (<25 years) than older drivers. These results confirm the need for interventions targeting risky driving and suggest that different strategies may be required for different high-risk groups.     

The influence of passengers on the risk of the driver causing a car collision in Spain. Analysis of collisions from 1990 to 1999

Objective: To determine how the number of passengers, their age and their sex influence the risk of different types of Spanish drivers causing a collision between two or more cars.Methods: We selected, from the Spanish database of traffic crashes resulting in personal injuries or death, those collisions between two or more cars that occurred between 1990 and 1999 in which only one of the involved drivers committed a driving infraction. These drivers were considered the cases; non-infractor drivers were considered their matched controls. We collected information on the number, age and sex of the passengers in each vehicle, along with some potential confounding variables of the drivers and the vehicles involved. Crude and adjusted odds ratios were calculated for the main categories of driver and passenger.Results: A protective effect for the presence of passengers was detected (adjusted odds ratio: 0.69; 95% CI: 0.67-0.70). The protective effect was higher for drivers aged more than 45 years and lower for the youngest drivers (<24 years old). The strongest association was observed for female passengers who accompanied male drivers. The protective effect was lower for passengers older than 64 years.Conclusion: Our results suggest that drivers are less likely to cause a car collision between two or more cars that results in personal injuries or death when they are accompanied by passengers, regardless of driver or passenger characteristics.     

Time vs. distance as measures of exposure in driving surveys

A survey of drivers carried out in Ontario in 1988 has provided data on time spent driving as well as the distances driven for licensed drivers of both sexes in six age groups and three regions. Substantial differences were found in times, distances, and distance/time ratios among these groups. Men drove 50% greater distances, but spent only 30% more time driving than women; speed, averaged over each day's driving, was lower for older drivers than for younger drivers. Differences in speed reflect differences in the driving done in urban or rural areas, and differences in the opportunity for road crashes; such differences, whether based on units of time or distance, will also affect both the comparisons of accident rates and the perceptions of risk among different groups of drivers. A definition of exposure to risk of road crash is required that considers both time and distance appropriately.     

Findings from the Candrive/Ozcandrive study: Low mileage older drivers,crash risk and reduced fitness to drive

Previous research has found that only older drivers with low annual driving mileages had a heightened crash risk relative to other age groups. These drivers tend to drive mainly in urban areas, where the prevalence of complex traffic situations increases crash risk. However it might also be that some drivers may have reduced their driving due to perceived or actual declines in driving fitness.     

The effects of age and workload on 3D spatial attention in dual-task driving

In the present study we assessed whether the limits in visual–spatial attention associated with aging affect the spatial extent of attention in depth during driving performance. Drivers in the present study performed a car-following and light-detection task. To assess the extent of visual–spatial attention, we compared reaction times and accuracy to light change targets that varied in horizontal position and depth location. In addition, because workload has been identified as a factor that can change the horizontal and vertical extent of attention, we tested whether variability of the lead car speed influenced the extent of spatial attention for younger or older drivers. For younger drivers, reaction time (RT) to light-change targets varied as a function of distance and horizontal position. For older drivers RT varied only as a function of distance. There was a distance by horizontal position interaction for younger drivers but not for older drivers. Specifically, there was no effect of horizontal position at any given level of depth for older drivers. However, for younger drivers there was an effect of horizontal position for targets further in depth but not for targets nearer in depth. With regards to workload, we found no statistically reliable evidence that variability of the lead car speed had an effect on the spatial extent of attention for younger or older drivers. In a control experiment, we examined the effects of depth on light detection when the projected size and position of the targets was constant. Consistent with our previous results, we found that drivers’ reaction time to light-change targets varied as a function of distance even when 2D position and size were controlled. Given that depth is an important dimension in driving performance, an important issue for assessing driving safety is to consider the limits of attention in the depth dimension. Therefore, we suggest that future research should consider the importance of depth as a dimension of spatial attention in relation to the assessment of driving performance.     

Age differences in simulated driving performance: Compensatory processes

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

Personality and attitudes as predictors of risky driving among older drivers

Although there are several studies on the effects of personality and attitudes on risky driving among young drivers, related research in older drivers is scarce. The present study assessed a model of personality-attitudes-risky driving in a large sample of active older drivers. A cross-sectional design was used, and structured and anonymous questionnaires were completed by 485 older Italian drivers (Mean age = 68.1, SD = 6.2, 61.2% males). The measures included personality traits, attitudes toward traffic safety, risky driving (errors, lapses, and traffic violations), and self-reported crash involvement and number of issued traffic tickets in the last 12 months. Structural equation modeling showed that personality traits predicted both directly and indirectly traffic violations, errors, and lapses. More positive attitudes toward traffic safety negatively predicted risky driving. In turn, risky driving was positively related to self-reported crash involvement and higher number of issued traffic tickets. Our findings suggest that theoretical models developed to account for risky driving of younger drivers may also apply in the older drivers, and accordingly be used to inform safe driving interventions for this age group.     

Driver age, car mass and accident exposure— A synthesis of available data

The tendency of younger drivers to be more likely than older drivers to drive smaller cars has been an important consideration in a number of prior investigations of the relation between car size and traffic safety. The purpose of the present study is to quantify this effect on a firmer basis than hitherto by fitting data from seven independent sources to a unified general model. More specifically, when the exposure measures “per unit distance of travel” or “per registered car” are used in studies of car mass effects on traffic safety, the exposure information often does not contain the variable driver age. This work develops a general procedure for disaggregating such exposure data into three driver (or owner) age categories; A₁: 16–24; A₂: 25–34; and A₃: 35 years. Data from the seven sources are fined to the equation

f(i,m) = H_i[1 + G _i(m/900 − 1)]

where m is the ear mass in kg, and f(i,m) is the fraction of cars of mass m which are driven (owned) by persons in the A_i, (i = 1, 2, 3) age category. The form of this equation permits easy comparison of 900 and 1800 kg cars. Those particular masses that have been chosen for illustrative comparisons in earlier work. The seven sets of data are used to derive overall average values of the parameters H₁ and G₁. The data from all seven sources show consistent effects which are summarized in one analytical expression which is well suited for use in future studies of car size effects because it reflects a synthesis of much prior data and it permits sensitivity analyses to be performed conveniently.     

Mild neuritic changes are increased in the brains of fatally injured older motor vehicle drivers

Given the expected increase in the older population and driving in this age group, concerns have been raised about the safety of older drivers. People over 65 years are over-represented in motor vehicle fatalities when calculated by distance driven. They are also at risk of neurodegenerative diseases, such as Alzheimer's disease, that affect cognitive function. We have examined the brains of older drivers (15M:12F) who died as a result of a motor vehicle accident (MVA) to determine the extent of Alzheimer's disease-related neurofibrillary changes (neuritic plaques and neurofibrillary tangles), Lewy body pathology and cerebrovascular disease and compared them to a control group of older licenced drivers (23M:5F) who died of other causes. The prevalence of moderate or severe neuritic plaque pathology was less than expected for the general population of this age and there was no difference between the groups. However, mild neuritic plaque pathology was increased for MVA deaths compared to controls. There was no evidence of vascular dementia or dementia with Lewy bodies. The current mandatory age-related re-licencing procedures in NSW may contribute to the low percentage of drivers with severe pathology. Further research into the role of mild pathology in cognitive impairment and older drivers is warranted.     

Perception of traffic risks for older and younger adults

The study examined differences in the perception of traffic risks for older and younger adults. Thirty-four younger participants (mean age 24.7 years) and 30 older participants (mean age 70 years) estimated the number of younger and older people (out of 100,000 people) that were injured in car and pedestrian crashes in a recent year. Both age groups viewed older adults’ risks in pedestrian crashes as higher than those of younger adults, and saw older adults’ risks in car crashes as identical to the risks for younger adults. Both age groups assessed the risks for their own group quite accurately, but erred in their assessment of the risk for the other group. Older participants tended to overestimate the risk for younger adults, and younger participants tended to underestimate the risk for older adults. These results point to the need to enhance awareness of the age-related increase in traffic risk, which could potentially promote more considerate driving behavior.     

Age-related declines in car following performance under simulated fog conditions

The present study examined age-related differences in car following performance when contrast of the driving scene was reduced by simulated fog. Older (mean age of 72.6) and younger (mean age of 21.1) drivers were presented with a car following scenario in a simulator in which a lead vehicle (LV) varied speed according to a sum of three sine wave functions. Drivers were shown an initial following distance of 18 m and were asked to maintain headway distance by controlling speed to match changes in LV speed. Five simulated fog conditions were examined ranging from a no fog condition (contrast of 0.55) to a high fog condition (contrast of 0.03). Average LV speed varied across trials (40, 60, or 80 km/h). The results indicated age-related declines in car following performance for both headway distance and RMS (root mean square) error in matching speed. The greatest decline occurred at moderate speeds under the highest fog density condition, with older drivers maintaining a headway distance that was 21% closer than younger drivers. At higher speeds older drivers maintained a greater headway distance than younger drivers. These results suggest that older drivers may be at greater risk for a collision under high fog density and moderate speeds.     

'Low mileage bias' and related policy implications--a cautionary note

This research examined a relationship asserted in recent literature in the field of traffic safety and injury prevention—that a significant indicator for elevated crash risk among older drivers, and potential trigger for individualized assessment at license renewal, is a low (<3000 km) annual driving distance. Sampling problems in earlier reports, in particular a reliance on self-report measures of both exposure and crash involvement, are highlighted. A pattern of misestimation for those who self-report an extremely low or extremely high number of miles driven is documented, that casts serious doubt upon the effect reported earlier. The present findings underscore the need for objective exposure measures for future analyses of this nature, and impact discussions about the feasibility of this suggested strategy to aid detection of at-risk older drivers by licensing officials.     

In defence of the ‘low-mileage bias’

There has been a long-recognised association between extent of driving and crash involvement: the lower the annual mileage driven, the higher the per-distance crash rate. Because older drivers generally drive less distance per year than others, this association has been used to explain much of their apparent over-involvement in crashes. Several studies from different countries around the world have demonstrated this ‘low-mileage bias’ and the relative safety of older drivers. However all studies have relied upon self-reported crash involvement and driving activity. Staplin et al. [Staplin, L., Gish, K., Joyce, J., 2008. ‘Low mileage bias’ and related policy implications—a cautionary note. Accident Analysis and Prevention 40, 1249–1252] have drawn attention to the discrepancy between self-reported and odometer-based driving distances and have argued against the credibility of the low-mileage bias. This paper has re-worked initial data from an early study which supported low-mileage bias, this time using odometer-based readings rather than self-reported mileage. Accepting the odometer readings at face value, the low-mileage bias remains evident, albeit at a reduced level.     

Driving performance during concurrent cell-phone use: are drivers aware of their performance decrements?

Prior research has documented the manner in which a variety of driving performance measures are impacted by concurrent cell-phone use as well as the influence of age and gender of the driver. This current study examined the extent to which different driver groups are aware of their associated performance decrements. Subjects' confidence in dealing with distractors while driving and their ratings of task performance and demand were compared with their actual driving performance in the presence of a cell-phone task. While high confidence ratings appeared to be predictive of better driving performance for male drivers (as confidence increased, the size of the distraction effects decreased), this relationship did not hold for females; in fact, for older females, as confidence increased, performance decreased. Additionally, when drivers were matched in terms of confidence level, brake responses of older females were slowed to a much greater extent (0.38 s) than were brake responses of any other group (0.10s for younger males and females and 0.07 s for older males). Finally, females also rated the driving task as less demanding than males, even though their performance was more greatly affected by distraction. These results suggest that many drivers may not be aware of their decreased performance while using cell-phones and that it may be particularly important to target educational campaigns on driver distraction towards female drivers for whom there tended to be a greater discrepancy between driver perceptions and actual performance.     

Factors related to driving difficulty and habits in older drivers

OBJECTIVES: To evaluate the association between chronic medical conditions, functional, cognitive, and visual impairments and driving difficulty and habits among older drivers. DESIGN: Cross-sectional study. SETTING: Mobile County, Alabama. PARTICIPANTS: A total of 901 residents of Mobile County, Alabama aged 65 or older who possessed a driver's license in 1996. MEASUREMENTS: Information on demographic characteristics, functional limitations, chronic medical conditions, driving habits, and visual and cognitive function were collected via telephone. The three dependent variables in this study were difficulty with driving, defined as any reported difficulty in > or = 3 driving situations (e.g. at night), low annual estimated mileage, defined as driving less than 3000 miles in 1996, and low number of days ( < or = 3) driven per week. RESULTS: A history of falls, kidney disease or stroke was associated with difficulty driving. Older drivers with a history of kidney disease were more likely to report a low annual mileage than subjects without kidney disease. Low annual mileage was also associated with cognitive impairment. In general, older drivers with a functional impairment were more likely to drive less than 4 days per week. Older drivers with a history of cataracts or high blood pressure were more likely to report a low number of days driven per week, while subjects with visual impairment were at increased risk of experiencing difficulty driving as well as low number of days driven per week. CONCLUSIONS: The results underscore the need to further understand the factors negatively affecting driving independence and mobility in older drivers, as well as the importance of improved communication between older adults and health care professionals regarding driving.     

Driving strategies among younger and older drivers when encountering children

Results are presented of a study into how drivers say they behave and how they actually behave in traffic situations in which children are involved. An analysis was made of the most important types of encounters in which drivers become involved in accidents with children. On the basis of accident surveys and psychological theories on information processing, it was assessed by means of a questionnaire what knowledge drivers have concerning their own behavior in these situations, as well as their expectations about typical child behavior. Actual behavior of drivers in these situations was investigated by assessing video recordings of their behavior in driving a one hour standard track through residential areas. From the questionnaire it appeared that younger drivers reported more frequently dangerous behavior than older drivers. The recordings showed that younger drivers also behaved more dangerously during child encounters. This result could not be explained by differences in speed, but could by the fact that younger drivers detected the children less frequently than older drivers. Implications for the contents of mass media campaigns and their evaluation are discussed.     

A longitudinal investigation of the predictors of older drivers’ speeding behaviour

There is little objective evidence about the extent older drivers’ are involved in speeding or factors that may influence this behaviour. Particular concern exists for the increasing number of older drivers with poor or declining cognitive and visual function. This study investigates whether a reduction in speeding forms part of the self-restrictive driving behaviour evident when older drivers experience poor cognitive and visual function. Driving data over 12 months were collected from 182 volunteers aged 75–94 years. Driving speed was estimated using Global Positioning System location, and speed limit data was based on a service-provider database. Speed events were defined as driving 1 km/h or more, with 3% tolerance, above a single speed limit, averaged over 30 s. Almost all participants (99%) were involved in speed events. While, 16–31% of participants experienced a meaningful decline in cognitive or visual function during the 12-months, these declines were not predictive of a change in speed events. Our results indicate speeding behaviour in this age group was highly prevalent, but less so for the oldest drivers whereby the rate of speed events was 7% lower per year older (IRR = 0.93, 95%CI = 0.89–0.96). Older drivers with worse function were less involved in speed events (unadjusted for distance driven) during 12 months of observation. Weekly distance driven decreased over the year by approximately 0.45 km with every week of monitoring for these older drivers. When distance driven was taken into account, decreased function was not predictive of involvement in speed events, indicating the reduction in speed events may be achieved by older drivers with lower function reducing distance driven. These results are important for developing policy to address speeding behaviour of the growing population of older drivers to reduce the incidence of crashes and resulting casualties.     

Passenger vehicle safety in Australasia for different driver groups

Vehicle fleets in developed countries have benefitted from improved technology and regulation leading to safer vehicles. Nevertheless, for various reasons the public do not necessarily choose particular makes and models of cars according to their safety performance. This study aimed to identify areas for potential crashworthiness improvement in the Australasian fleets by studying the distribution of these fleets according to vehicle age and estimated crashworthiness. We used an existing database that encompassed the vast majority of the crash fleets studied, with existing estimates of crashworthiness generated by the Australasian Used Car Safety Ratings project. There were clear tendencies for older and younger people to be driving less safe vehicles that were also generally older. Given that older drivers are more fragile, and hence more liable to be injured in crashes, and younger drivers have a greater propensity to crash, it is clearly undesirable that these driver groups have the least crashworthy vehicles. Some suggestions are made to encourage safer vehicle choices.     

Perception of the risk of an accident by young and older drivers

Young drivers are significantly overrepresented among all drivers involved in traffic accidents and fatalities. Excessive risk taking by young drivers appears to be largely responsible for this disproportionate involvement. This excessive risk taking could be due to being more willing to take risks than older drivers are, failing to perceive hazardous situations as being as dangerous as older drivers do or both causes. This paper reports the results of a study which attempted to determine whether misperception of risk could be an explanation for the high rates of traffic accidents among youth by testing whether young drivers perceive driving to be less hazardous than do older drivers. Three different methods of estimating the risk of accident involvement were used to compare risk estimates of young and older drivers. The methods included general questions about accident involvement, rating the riskiness of ten specific driving situations illustrated in still photographs, and rating the riskiness of fifteen videotaped driving situations. Young drivers perceived their own chances of an accident to be significantly lower than those of both their peers and older male drivers, while older male drivers saw their chances of accident involvement as comparable to those of their male peers and less than those of young male drivers. These findings lend support to the thesis that young male drivers are overrepresented in traffic accidents at least in part because they fail to perceive specific driving situations as being as risky as older drivers perceive them.