Biomedical subjects

Michael D Keall

Publications and source records attributed to Michael D Keall.

6 recordsLinked to original sources

PubMed2006

Characteristics and risks of drivers with low annual distance driven.

OBJECTIVES: It has been noted by several authors that risk (defined only in terms of total expected numbers of crash involvements per total distance driven) paints a misleading picture of crash liability, particularly for the young and the old, as their high risk is associated with risky driving patterns typical of people who drive low annual kms. This article sets out to analyze these driving patterns of low-km drivers and to evaluate the risk of these patterns. As licensing programs tend to focus on young and old drivers, who tend to drive lower annual distances, income and employment data are also analyzed for low-km drivers. This is to provide a better picture for policy makers of the sort of people and the sorts of transportation requirements that their policies may affect. METHODS: Crash data and travel data were disaggregated by driver characteristics and by driving conditions (road type, day and night, weekend and weekday) and combined to form estimates of risk for typical driving patterns of driver groups. Characteristics of driving patterns and of the drivers themselves were derived for groups defined by age and by the amount of annual driving undertaken. RESULTS: Older drivers who drive less tend to have higher risk per km mainly due to their predominantly urban trips. Nevertheless, because older drivers on average manage to reduce their risk per distance driven by choosing driving patterns that are safer than the driving patterns of other age groups, the risk of older drivers as a group is not overestimated. CONCLUSION: Despite being quite different from one another, the low- and high-km driving patterns of younger drivers were found to impose identical risks.

Accidents, Traffic↗

PubMed2005

The contribution of alcohol to night time crash risk and other risks of night driving.

Many studies show that driving at night is more risky in terms of crash involvements per distance travelled than driving during the day. The reasons for this include the more prevalent use of alcohol by drivers at night, the effects of fatigue on the driving task and the risk associated with reduced visibility. Although the consumption of alcohol prior to driving occurs most commonly at night, drink-driving is not inherently a night time risk factor. This study decomposes the New Zealand risk of driving at night into risk associated with alcohol and risk associated with inherently night time factors. The overall risk associated with alcohol use by drivers was shown to decrease with increasing age for the most risky situation analysed (male drivers on weekend nights). Given the levels of drinking and driving on weekend nights, the overall effect of alcohol was shown to contribute almost half of weekend night time risk for drivers aged under 40 on lower volume roads, but to contribute little to overall risk on higher-volume roads, consistent with other research showing that higher-volume roads are not favoured by drinking drivers. Risk at night relative to risk during the day (excluding risk associated with drinking and driving) was shown to decrease with age. Roads with illumination at night are less risky at night relative to during the day than roads without illumination. The risks estimated in this paper reflect the behaviour of the road users studied and their prevalence on the roads under the conditions analysed.

Accidents, Traffic↗

PubMed2004

The influence of alcohol, age and number of passengers on the night-time risk of driver fatal injury in New Zealand.

Breath alcohol measurements and other data collected at randomly selected roadside sites were combined with data on fatally injured drivers in crashes occurring on the same weekdays and times (Friday and Saturday nights) at locations matched by the size of the nearest town. A logistic model was fitted to these data for the years 1995-2000 to estimate the effects of alcohol, driver's age and the influence of passengers carried on the risk of driver fatal injury in New Zealand. The estimated risks increased steeply with increasing blood alcohol concentration (BAC), closely following an exponential curve at levels below about 200mg/dl (i.e. 0.2%) and increasing less than exponentially thereon. The model fitted to data for drivers under 200mg/dl showed that risks at all BAC levels were statistically significantly higher for drivers aged under 20 (over five times) and for drivers aged 20-29 (three times) than for drivers aged 30 and over. Further, controlling for age and BAC level, driving with a single passenger was associated with approximately half the night-time risk of driver fatal injury relative to driving either solo or with two or more passengers. According to a recent travel survey, the types of passengers carried at the times of night and days of week studied appear to differ significantly from the types of passengers carried generally, which may lead to different passenger effects on driver behaviour. The high relative risk of teenage drivers means that they reach high risk levels commonly regarded as unacceptable in the field of road safety even at their current legal limit of 30mg/dl, particularly when more than one passenger is carried in the car.

Accidents, Traffic↗

PubMed2004

Older driver crash rates in relation to type and quantity of travel.

It is a well-established phenomenon that, notwithstanding their overall good crash record, older drivers have a higher than average rate of involvement in injury crashes when the rate is calculated by dividing crash numbers by distance driven. It has been hypothesised that at least some of this higher crash rate is an artefact of the different nature of driving undertaken by many older drivers. For example, driving in congested urban environments provides more opportunities for collisions than driving the same distance on a motorway. However, there have been few opportunities to investigate this theory, as relevant data are difficult to acquire. High-quality data from the New Zealand Travel Survey (1997/1998) were combined with crash data to enable a statistical model to estimate the risk of driver groups under various driving conditions characterised by the type of road used, time of day, day of week, and season of year. Despite elevated crash risks per distance driven compared with middle-aged drivers for most road types, older drivers were as safe as any other age group when driving on motorways. Accounting for the fragility of older drivers and their passengers in the risk estimates for other road types, older drivers appeared to have daytime risks comparable to 25-year-olds and night-time risks as low as any other age group. The driving patterns of older drivers (in terms of when and where they drive) were estimated to minimize their risks in comparison with the driving patterns of other age groups. These results are of interest to both policy makers and transportation planners working against the background of inevitable increases in the number of older drivers as the population ages.

Accidents, Traffic↗

PubMed2004

Association between older driver characteristics, on-road driving test performance, and crash liability.

From May 1999, a new system for licensing older drivers was introduced in New Zealand. It included a practical on-road driving test with expanded scope, to be completed every two years from the time the driver turns 80. The relationship between crashes and test performance needed to be studied to inform the debate regarding the testing system. The population studied was all drivers who entered this licensing system during its first three years of operation. They were defined as crash involved if they were involved in an injury crash during the two years following their first licensure under the new system. Logistic regression was used to describe the risk of crash involvement in terms of driving test performance and other driver characteristics. Each driving test failure was associated with a 33% increase in the odds of crash involvement (95% CI 14% to 55%), controlling for age, gender, minor traffic violations, and whether the older driver lived with another licensed driver or not. Minor traffic violations in the two years following the driving test were associated with twice the odds of crash involvement. These results suggest that the new on-road driving test does identify older driver behaviors or limitations that are related to crash liability. It is anticipated that the results presented here will provide essential information for discussing older driver licensing systems, whose impact will grow in importance as the population of drivers ages.

Accidents, Traffic↗

PubMed2002

Further results from a trial comparing a hidden speed camera programme with visible camera operation.

As described in a previous paper [Accident Anal. Prev., 33 (2001) 277], the hidden camera programme was found to be associated with significant net falls in speeds, crashes and casualties both in 'speed camera areas' (specific signed sites to which camera operation is restricted) and on 100 km/h speed limit roads generally. These changes in speeds, crashes and casualties were identified in the trial area in comparison with a control area where generally highly visible speed camera enforcement continued to be used (and was used in the trial area prior to the commencement of the trial). There were initial changes in public attitudes associated with the trial that later largely reverted to pre-trial levels. Analysis of 2 years' data of the trial showed that falls in crash and casualty rates and speeds associated with the hidden camera programme were being sustained. It is not possible to separate out the effects of the concealment of the cameras from other aspects of the hidden speed camera programme, such as the four-fold increase in ticketing. This increase in speed camera tickets issued was an expected consequence of hiding the cameras and as such, an integral part of the hidden camera programme being evaluated.

Accidents, Traffic↗