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91�Թ� researchers say U.S. motorists are more prone to fatal road crashes on income tax deadline day (typically April 15th) than normal days.

A new study in the Journal of the American Medical Association (JAMA), led by Dr. Donald Redelmeier, a professor in the Department of Medicine, found the increased risk on tax day included passengers and pedestrians and extended across different regions, daylight hours, demographic groups and alcohol consumption.

“The increased risk could be the result of stressful deadlines leading to driver distraction and human error,” said Redelmeier. “Other possibilities might be more driving, sleep deprivation, lack of attention and less tolerance toward hassles.

"Another contributor could be decreased law enforcement as the police, themselves, might be busy with their own tax deadlines.”

Using road safety information for the entire United States from the National Highway Traffic Safety Administration for thirty years (1980 through 2009), Redelmeier and 91�Թ� colleague Christopher Yarnell examined the number of fatal crashes on each tax deadline day as well as the same weekday one week before and after to control for prevailing risks.

Their analysis observed a total of 19,541 individuals involved in fatal crashes during the 30 tax days and 60 control days. The 30 tax days accounted for 6,783 individuals, equivalent to 226 per day. In contrast, they observed a total of 12,758 individuals during the 60 control days, equivalent to 213 per day. Hence, the risk was 6% higher on income tax deadline day and equal to an absolute increase of 404 deaths over the study or about 13 individuals for the average tax day.

The greatest increases in risk with tax deadlines were during the last twenty years and mostly related to working age adults under age 65 years. 

Risks could be mitigated by simple measures such as reminding patients of the importance of safe driving, the researchers said.  Basic instructions include emphasizing the need to wear seatbelts, avoid excessive speed, minimize distractions, and avoid alcohol.  Almost all fatal crashes can be avoided by a small change in driver behaviour. 

Redelmeier, a professor of medicine at Sunnybrook Health Sciences Centre (Canada's largest trauma centre) said: “The increased risk of fatal crashes on tax deadline days imparts a substantial cost to society. In theory, the net losses equate to about $40 million in societal costs that could mathematically negate the income tax payments of about 5,000 average Americans each year.”

The study was supported by the Canada Research Chair in Medical Decision Science and the Canadian Institutes of Health Research. The results of the study are published in the April 11, 2012 issue of JAMA.