"When drivers try to speed to get to their destination faster, they actually lose more time because the savings from faster travel are offset by the increased prospect of a crash," said lead investigator Dr. Donald Redelmeier, a staff physician at Sunnybrook Health Sciences Centre in Toronto.
"The 20-minute penalty for each hour spent driving... is completely invisible to most drivers. But it is there lurking in the background, and at the end of the year, it adds up to about 45,000 deaths." (About 3,000 people in Canada and almost 42,000 in the United States die in motor vehicle accidents each year.)
A study with co-author Dr. Ahmed Bayoumi recommends that easing back on the pedal even a bit could pay significant dividends over time.
"The estimates suggest that slowing down slightly by about three kilometres an hour would cost average drivers about three minutes daily in trip time, but save them about three hours annually in overall survival," Redelmeier said.
Applied at the population level, even a three km/h speed reduction could provide a huge benefit, he stressed. In the United States, for example, the slower speed would translate into about three million fewer crashes causing property damage, one million fewer crashes causing injury and 9,000 fewer deaths each year.
"The point here is the average driver out there isn't so far off, they are just slightly off and they are off in the direction of going slightly too fast.
"So it boils down to a reminder to slow down, because haste makes waste."
The study, published in Monday's issue of the Journal of Medical Decision Making, used a complex formula for estimating reduced life expectancy. It was based on a combination of computerized traffic modelling, U.S. national statistics covering driving on public roadways and the laws of physics.
The computer models took into account average distances and the time that drivers in the United States travel daily, the number of annual crashes categorized as fatal, injurious and causing property damage, as well as the expected time losses due to crashes of varying severity.
For any driver who wonders how such an estimate affects them personally, Redelmeier said the risk of a potentially deadly or injurious accident occurring exists even for the most mundane reasons for getting behind the wheel. Think of grocery shopping, a doctor's appointment or running the kids to school.
"For every person who died in a motor vehicle crash, there are about 50 other people who are left permanently disabled," he said, including those with spinal cord and traumatic brain injuries or chronic pain syndromes from multiple fractures.
-- The Canadian Press