In 2004, women's life expectancy exceeded men's life expectancy by 5.2 years, the smallest gender gap in life expectancy since 1946. Life expectancy for whites was five years greater than that of blacks. Life expectancy for black and white men and women was as follows: 1  Black male: 69.8 years.  White male: 75.7 years.
But, that's not always the case. Safe following distances vary according to traffic speed and weather conditions and according to the type of vehicle you're driving. In good conditions, you should allow 2 seconds between your car and the vehicle in front of you. Here's an easy way to work that out.
A properly set speed limit will be within 3 miles per hour (Â±) of this observed speed. The posted speed limit will then be rounded to the nearest 5 miles per hour. Research has shown that the 85th percentile speed is the speed where accident involvement is the lowest. Reducing the speed limit below what is warranted can actually be detrimental to safety.