Stopping distance is the distance needed to bring a moving vehicle to a complete stop, and understanding this principle is incredibly important. If you’re not able to accurately calculate stopping distance, you run the risk of serious accident, resulting in property damage and bodily injury to yourself and others — or even death.
The following driver safety facts give you the information you need to help you control and stop your vehicle.
Perception distance
Perception time is the three-quarters of a second it takes for you to realize — after your eyes see a hazard — you need to brake. So, if you’re driving at 65 mph, your vehicle will travel 71 feet before you realize you need to start braking.
Reaction distance
Reaction time is also three-quarters of a second. This time, it’s the time you take to move your foot from the accelerator to the brake. Again, at 65 mph, that’s another 71 feet traveled.
So far, your vehicle has traveled 142 feet and you haven’t even touched the brake.
Braking distance
Braking distance is the distance it takes to stop your vehicle once you apply the brakes. At 65 mph, it takes an additional 5.5 seconds or about 525 feet of actual brake application to stop your vehicle.
Stopping distance
Stopping distance is the total distance needed to bring your vehicle to a complete stop. To determine the stopping distance, you calculate: Perception Distance (71 feet) + Reaction Distance (71 feet) + Braking Distance (525 feet) = Stopping Distance (667 feet)
Common sense also says when conditions change, times and distances change too. Age of equipment, speed, traffic, weather, road surface, the weight of your load, and the condition of your tires and brakes are among the factors that can affect one or more of these elements and increase the total stopping distance.
It’s important to know that an empty truck requires a greater stopping distance than a fully loaded truck, because an empty truck has less traction, meaning there is less friction between the tires and the road. An empty truck may also bounce and lock up its wheels, resulting in poor braking capacity.
Wet roads can significantly reduce your ability to stop your vehicle. In general, wet roads can double your stopping distance. In order to stop a vehicle on a wet road using the same stopping distance as a dry road, you will need to drive slower. On wet roads, you should reduce your speed by about one-third, or from 65 mph to around 43 mph. On snow-covered roads, you should reduce your speed by at least one-half. This will help ensure that you have an adequate stopping distance.
There are a number of signs you can look for to help you identify potentially hazardous and slippery road conditions:
- Shady sections of the road stay wet and icy longer than sunny sections.
- Bridges freeze before roads.
- When ice begins to melt, road surfaces become wet and slippery.
- Black ice makes a road appear wet, but in actuality, the road is frozen over.
- Icy vehicle mirrors and antennas are good indicators of impending icy roads.
- When it first begins to rain, water mixes with oil from vehicles, making roads extremely dangerous.
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