Final answer:
Passenger cars and light trucks should maintain at least a three-second following distance from the vehicle ahead in ideal driving conditions, according to the three-second rule.
Step-by-step explanation:
In ideal driving conditions, passenger cars and light trucks should maintain a minimum of three seconds following distance behind the vehicle they are following. This rule is often referred to as the three-second rule, which helps drivers maintain a safe traveling distance to avoid collisions. To determine if you are following this rule, select a fixed point on the road ahead such as a sign or a tree. When the vehicle in front of you passes that point, begin counting seconds ('one thousand one, one thousand two, one thousand three'). If you reach the same point before you finish counting, you are following too closely and should increase your distance.