FORT LAUDERDALE --- Those two certainties in life - death and taxes – appear to collide on Tax Day.

A new study has found deadly auto accidents increase on the day of the IRS deadline to file income tax returns. Researchers don't know why – perhaps distracted are drivers worried about their taxes, or motorists are rushing to file on time. But one thing's for sure: If you're on the road in South Florida Monday, you need to be extra careful.

The study, by University of Toronto researchers, examined nearly three decades of car accident reports compiled by the National Highway Traffic Safety Administration. Researchers led by Dr. Donald Redelmeier compared the number of fatal car accidents occurring on tax day (usually on or around April 15) to those the week before and the week after, between 1980 and 2009.

Their findings, published in the Journal of the American Medical Association: 19,541 people were involved in fatal crashes on tax days over that 30-year-period — 6 percent more than on a typical day.

The underlying causes aren't clear, but the researchers said stress is likely a factor.

"U.S. income tax day ... is a stressful deadline for millions of U.S. adults," they concluded. "We investigated the number of individuals involved in a fatal road crash on tax day under the pre-specified hypothesis that stressful deadlines might increase the risk of road trauma by impairing drivers or by compromising surrounding individuals from making compensatory adjustments."

This year, the Internal Revenue Service postponed the deadline by two days, to April 17, because April 15 is a Sunday and the next day is Emancipation Day - a public holiday in Washington, D.C.

Taxpayers can call the free IRS hotline for general tax information at 800-829-1040.