Tax time. Two words that fill millions of Americans with dread. It turns out that there's more to worry about at tax time than just money. People also need to worry about getting on the road. Fatal road accidents rise every year on the date that income taxes are due.

Researchers from the University of Toronto thought that stress from the yearly tax deadline might lead to more road accidents. So they sifted through 30 years of National Highway Traffic Safety Administration records and compared the number of people involved in fatal car crashes on the date income tax was due to the number involved one week before and one week after the due date. They found that the risk of being in a fatal road accident rises on tax day, on or around April 15th every year.

The traffic fatality risk on tax day has increased in the last two decades. E-filing may have made paying taxes more convenient, but it still doesn't take the sting out of paying them.

On average, about 13 additional people were involved in fatal car crashes every tax day, an increased risk of about 6%. This may sound small, but it happens every year. And the risk has increased in the last two decades, with 1990-2010 being more hazardous than 1980-1990 was.

E-filing may have made paying taxes more convenient, but it still doesn't take the sting out of paying them.

The increased risk was found in all regions of the country, though it was highest in the West. It was seen in both urban and rural areas, for all times of day, for both sexes and also for passengers and pedestrians. It affects almost everyone. Only people over 65 seem to be immune.

The researchers suggest that the main cause is stress, which distracts drivers and leads to more accidents. A Gallup poll found that April 18, the date taxes were due in 2011, was the second most stressful day of that year. Only April 27, when one of the largest tornado outbreaks ever recorded tore through the southeastern U.S. and killed more than 300 people, surpassed it.

The researchers also speculate that sleep deprivation, alcohol consumption, altered driving patterns and a simple tax-related increase in orneriness may all play a role in the added danger. But it's not speculation that the roads are less safe on the day when taxes are due and won't get safer until drivers make them so.

This year, taxes are due April 17. It's a good day to pay a little extra attention when out on the road or when crossing it.

The results of the study were published in a research letter appearing in the April 11, 2012 issue of The Journal of the American Medical Association (JAMA).