This operating procedure is the setting and holding of an appropriate vehicle following-distance - one that permits you to make safe, controlled stops in all circumstances.
A safe following distance in traffic is always important, but never more than when the weather reduces visibility and traction - and increases your chances for skids, spins and crashes. In such conditions, you must pay special attention to putting more space between you and the vehicle ahead of you.
Question is: How much space is enough? Let's figure.
Remember: Even under what the pros call "ideal" driving conditions - dry, clear, daylight - the rule of thumb for an adequate following distance by a heavy, air-braked vehicle is an interval of at least four seconds between you and the vehicle ahead. To calculate:
- Observe the leading vehicle as it passes an abutment, tree, or other landmark. Then count to four: One-thousand one... One-thousand two... One-thousand three. One-thousand four.
- If you reach the landmark before you have finished counting, you're too close.
- Back off until the interval reaches at least four seconds.
- Continue adjusting if other vehicles move ahead of you into the gap.
This formula applies only to optimal driving conditions. So when bad weather sets in, you'll have to compensate.
How? Some experts suggest using what amounts to "safety spacers" - One or more seconds of additional interval for each negative driving element you encounter.
Building on your base of at lease four seconds, you should increase the following-distances as driving conditions deteriorate. The worse the weather, the greater the gap should grow between you and the vehicle ahead. For example, you might track on:
- One second for darkness.
- Another second for rain.
- Multiply seconds - each - for snow, ice, or fog.
- And so on.
Of course, these weather-related adjustments are only approximate. And what you actually do depends - like so much in driving - on your own experience, judgment, and individual circumstances.
For instance, there could come a time when the interval grows so large, and conditions grow so poor, that you can't stay in contact with the leading vehicle.
At that point, unable to see the vehicle ahead, you may no longer be able to calculate a "safe distance" for following - meaning that you might have to get off the road.
If that happens, pull your vehicle to a safe place and follow company and regulatory policies covering your situation.
You can get rolling again once condition improve, confident that you're always in control - no matter what the weather throws at you.