One hour of driving could reduce life by 20 minutes [or 7.2 minutes]

From Canwest News Service One hour of driving could reduce life by 20 minutes: Study

TORONTO — Researchers at a Toronto hospital say that every hour spent driving could lead to a 20-minute loss in life expectancy.
Using complex computer models, a team at Sunnybrook Health Sciences Centre determined that, much like how each cigarette smoked takes about five minutes off of a person’s life, the more time spent behind the wheel, the more likely a person is to die in a car crash.
“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 Dr. Donald Redelmeier, the study’s lead researcher.
But the study also found that slowing down the average speed of North American drivers by just three kilometres an hour “yielded 11,000 fewer crashes each day, saved about $10 million from property damage each day, and conserved about 199 cumulative life years” across the continent.
The research was published in the latest edition of the journal Medical Decision Making.

I couldn’t find the article, but I was curious, so I used a non-complex model …
Back of the envelope, people spend 365 hours in a car each year and live 80 years. So 365*80=29,200 hours. (About an hour a day, a rough average for a lifespan, too high for children, too low for active adults).
In the US there are about 40,000 car deaths per year, and assume average life expectancy is 80 years. In 80 years there will be 3.2 million car deaths. If US population is about 320 million (which it will be by 2020), there is about a 1% chance of dying in a car crash over a lifespan. Assume the death occurs at age 40, there will be 40 years of life lost (or 350,400 hours). A 1% chance of a 40 year loss gives an expected lost of 3504 hours.
If everything is linear (which it isn’t), for each hour driving you lose .12 hours (7.2 minutes), about 1/3 of the 20 minutes claimed in the article.