Age, Gender Major Factors In Severity Of Auto-accident Injuries

The new findings are especially important because the number of drivers 65 and older is expected to double by 2030 in the United States to 70 million, said Fred Mannering, a professor of civil engineering at Purdue University and the study's co-author. National statistics show that fatalities rose by 7 percent for drivers 75 and older from 1981 to 2000, remained steady for drivers from 65-74, but dropped for younger drivers.

"It is reasonably well known that age and gender have an effect on the likelihood of an accident, but the influence that age and gender have on driver injuries once an accident has occurred is not well understood," Mannering said.

The Purdue researchers found statistically significant differences in the severity of injuries suffered in accidents involving men and women drivers and drivers within three age groups: young drivers, 16-24; middle-aged drivers, 25-64; and older drivers, 65 and above.

"Because the factors that affect how severely you are going to be injured vary depending on your age and gender, a better understanding of age and gender differences can lead to improvements in vehicle and highway design to minimize driver injury severity," Mannering said. "What is clear is that safety research and policy must begin to seriously address gender- and age-related matters because there are compelling differences and considerable potential to improve safety if these differences are properly addressed."

Findings were detailed in a paper published last year in the Journal of Safety Research. The paper was written by Purdue doctoral student Samantha Islam and Mannering.

The researchers used mathematical models to calculate various probabilities using data from one-vehicle accidents in Indiana.

The study included findings showing that:

• Accidents involving an overturned vehicle increased the likelihood of a fatality by 220 percent for older men and only 154 percent for young men. For women, rollover accidents increased the likelihood of fatality by 523 percent for older women and only 116 percent for young women.
• Vehicles carrying one or more passengers at the time of the accident increased the likelihood of driver fatality by 114 percent for young men and 70 percent for middle-aged men, but had no significant effect on the injury levels of older male drivers.
• Vehicles less than five years old increased the likelihood of fatality for older men by 216 percent and for young men by 71 percent, but did not have a significant effect on the likelihood of a fatality for middle-aged men.
• Not using safety belts increased the likelihood of injury by 119 percent for young women, 164 percent for middle-aged women and 187 percent for older women.
• Accidents occurring in rural areas increased the likelihood of fatalities by 208 percent for young women but had no significant effect on the injury levels of other female age categories.
• Vehicles six years old and older increased the likelihood of injury for middle-aged female drivers by more than 200 percent but had no significant impact on the injury levels of other female age categories.
• Fatalities were more likely for middle-aged men who fall asleep at the wheel, exceeded the speed limit, got into an accident at an intersection or had an accident after midnight on Friday or Saturday, while the same factors had no significant effect on the injury levels of middle-aged female drivers.
• Injuries were shown to be more likely for middle-aged women who drive during daytime hours, drive while under the influence of alcohol or drive while ill, while the same factors did not significantly influence the injury levels of middle-aged male drivers.
• Driving on curvy roads and driving vehicles six years old and older increased the likelihood of injury for middle-aged female drivers but were found to have no significant effect on the injury levels of middle-aged male drivers.

"We can only speculate as to why these differences exist," Mannering said. "Possibilities include differences in reaction time and physical differences relating to height, weight and body structure and vehicle design attributes that affect drivers differently. Another possibility is that vehicle safety systems, such as safety belts and airbags, may be more effective for some age and gender categories than for others."

While alcohol played a role in some categories, such as middle-aged female fatalities, its impact was not statistically significant for most age and gender categories, Mannering said.

"In many cases, alcohol consumption may have an indirect effect by increasing the probability of not wearing a safety belt, speeding and the likelihood of certain types of collisions, but once you know these factors, the direct effect of alcohol on injury severity may not be statistically significant," he said. "For the most part, if you are drunk and hit a utility pole at 70 mph, you will have the same injury probabilities as if you are sober and hit a utility pole at 70 mph. On the other hand, whether you would have been going 70 mph and hit the utility pole if you were sober is another question — one that we do not address in this paper because our statistical models are conditioned on the accident having occurred."

Future areas of research should be pursued, Mannering said, including an expansion of analyses to consider accidents involving more than one vehicle and accidents in other geographical areas; analyses of the effect of various vehicle safety systems on drivers of different height, weight and body structures; and comprehensive analyses of male and female age-related responses in accident situations.