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.
The recommended advance placement distances in Table 2C-4 are 1) stopping sight distance values for the stated speed minus 180 feet for Condition A (for Speed reduction and Lane changing in heavy traffic) and 2) stopping sight distance minus 250 feet for Condition B (decelerating to a stop condition).