Use __________ to ensure that you are not driving faster than the distance you can see ahead.

Explanation

You must not drive faster than the distance you can see ahead. The South Dakota Driver License Manual recommends the four-second sight distance rule for safe driving. Pick a stationary object that is as far ahead as you can see. Then count how many seconds it takes you to reach that object. If it takes you less than four seconds to reach it, you are driving too fast and may not be able to stop in time to avoid a hazard that far ahead. You should also use this rule at night to make sure that you are not "over-driving" your headlights.