A transportation engineer from The University of Texas at Austin has reviewed thousands of accidents and confirmed that seat belts reduce deaths, revealed what crash types are most deadly, and provided other detailed safety information.
The comprehensive review included 11,388 representative car crashes reported in 2003. Details about the crashes were reported to the General Estimates System, a data base of the National Highway Traffic Safety Administration regarding police-reported accidents.
Professor Chandra Bhat and civil engineering graduate student Naveen Eluru analyzed the selected crashes for driver characteristics, vehicle type, road conditions, and other factors to see what put drivers at greatest risk. They presented their findings Monday afternoon, Jan. 23, at the 85th annual meeting of the Transportation Research Board in Washington D.C.
Their report revealed that using seat-belt restraint systems greatly reduced the risk of death or severe injury. Those who suffered no injury, or a possible or slight injury, were mostly wearing seat belts. Moreover, Bhat’s study provided suggestive evidence that drivers who wear seat belts may drive safer to begin with, and therefore are at less risk of injury.
In comparison, drivers not wearing seat belts were four times more likely than drivers wearing seat belts to be involved in a serious injury, and 17 times more likely to die in crashes.
The engineers evaluated factors that contributed to driving without using a seat belt. This information might help in tailoring public-safety messages to increase seat-belt use.
“In the large scheme of things, the most important determinant of whether someone is wearing or not wearing a seat belt is driving under the influence of alcohol,” said Bhat, who holds the Fluor Centennial Teaching Fellowship in Engineering No. 1.
The report found that drivers who had been drinking were 15 percent less likely to wear seat belts than sober drivers. In addition, men, drivers younger than 25, and those who drove pickups were about 2 percent less likely to wear seat belts than women, drivers older than 25 years, and those driving non-pickup vehicles (sedans, sport utility vehicles or minivans), respectively.
Bhat noted that the latter result may be because some jurisdictions in the country exempt pickup drivers from wearing seat belts. The group also might include more commuters who drive in rural areas, where skipping this precaution might be considered more acceptable.
The report included statistics on the types of crashes that tend to put drivers most at risk. A crash where the driver is ejected from the car or the vehicle rolled over is most likely, on average, to cause severe injuries. Next in rank of danger is crashing into a large stationary object, or a head-on collision with another vehicle.
Somewhat less dangerous is crashing into a fire hydrant, guard rail or other small object, or colliding at an angle with another vehicle. Rear-end collisions are less dangerous on average than all of the above, and the least dangerous is a crash in which the driver’s car swipes another vehicle going in the same direction.
The study also revealed that: male and young-adult drivers (under age 25) are less likely to suffer severe injuries than women and drivers older than 25, respectively. Individuals over 74 years of age appear to be especially vulnerable to severe injuries in crashes. And drivers who are under the influence of alcohol are more likely to suffer severe injuries than sober drivers.
In terms of vehicle type, sedan drivers are most likely to be severely injured, particularly in the presence of snow or fog, or when hit by a non-sedan vehicle.
Bhat’s analysis also strongly suggested that seat-belt wearing drivers have unobserved factors that influence their propensity to avoid severe injury. This was determined using a mathematical equation that incorporated a variable to capture such unobserved factors, which could include better defensive driving habits compared to drivers who forgo seat belts.
These unobserved factors appear to be about equally important as seat belt usage itself in reducing the likelihood of a serious or fatal injury for seat-belt wearing drivers. If further research directly indicates that seat belt wearers are indeed safer drivers, Bhat said, that would indicate the need for law enforcement to consider mandating enrollment in a defensive driving course for drivers ticketed for not wearing a seat belt.
To view Bhat’s research paper about the comprehensive crash review, go to: www.ce.utexas.edu/prof/bhat/ABSTRACTS/Eluru_Bhat_seatbelt_use_rev_Nov1.doc.
To view a release about research Bhat presented earlier on Jan. 23 about children’s physical activity, go to: www.engr.utexas.edu/news/articles/20060117988/index.cfm.
To view a recent story about Bhat's new position as chair of an international travel research association, go to: www.engr.utexas.edu/news/articles/20060105982/index.cfm
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