SECTION 4.1
Approximate Stopping Distances

The Reaction Distance is the distance the car travels in the three-quarters of a second that it takes for a driver to react to a problem and apply the brakes.

The Braking Distance is the distance traveled from the time the brakes are first applied to the time the car comes to a complete stop.

The Stopping Distance is the total distance it takes to stop the vehicle, from the moment the driver sees a problem to the time the car is stopped completely.

Reaction Distance + Braking Distance
= Stopping Distance.

The following are approximate distances for an average passenger car with good brakes in good conditions on dry concrete:
At 20 mph:  Reaction Distance of 31 feet + Braking Distance of 36 feet = Stopping Distance of 67 feet.
This means that if you are traveling at only 20 mph, you have to allow 67 feet of stopping distance for your vehicle after recognizing a hazard.
At 40 mph Your Reaction Distance is 83 feet and your Braking Distance is 152 feet, resulting in a Stopping Distance of 235 feet.
At 60 mph Your Reaction Distance is 187 feet and your Braking Distance is 293 feet, resulting in a Stopping Distance of 480 feet.

Remember:

It takes much more distance to slow down from 70 mph to 50 mph than it does to go from 50 mph to a complete stop

Maintaining a Cushion Ahead

Many drivers don’t see as well as they should because they follow too closely, and the vehicle ahead blocks their view of the road. Good drivers keep a safe following distance so they can see better. The more space they allow between their car and the car ahead, the more time they will have to see a hazard or accident down the road. They will have more time to stop, or to avoid the hazard.

Steering will be easier if you have a "big picture" of your intended path of travel. Keep enough space between your car and the car in front of you, so that it does not block your view. Driving in the center of the lane, instead of hugging one side or the other, improves your view of the roadway.

Following too closely causes most rear end accidents. To avoid this, use the "three-second rule."  When the vehicle ahead of you passes a certain point, such as a sign, count "one-thousand-one, one-thousand-two, one-thousand-three."   This takes about three seconds. If you pass the same point before you finish counting, you are following too closely.  At faster speeds the distance should be greater.

Sometimes you will need more than a three-second cushion -- give yourself four seconds or more.

When a tailgater crowds you, you should allow extra room between your car and the car ahead. Then, if you need to slow down, you can do so gradually. You will be able to avoid braking suddenly and being hit from behind by the tailgater!
On slippery roads, if the car ahead should slow or stop, you will need more distance to stop your car.
When following motorcycles, if the motorcycle falls, you will have to avoid hitting the rider. Motorcycles fall more often on wet or icy roads, on metal surfaces such as bridge gratings or railroad tracks, and on gravel.
When the driver behind you wants to pass, slow down to allow room in front of your car so the driver will have space to move into.
When you are pulling a trailer or carrying a heavy load, the extra weight makes it harder to stop.
When following large vehicles that block your view ahead, you will need the extra room four seconds gives you to see around the vehicle and to the sides.
When you are stopped in traffic on a hill, the vehicle ahead may roll back into your car when it starts moving.
When you see a bus, school bus, or vehicle carrying flammables, remember that these vehicles must stop at railroad crossings. Expect the stops and slow down early to allow plenty of room.
When merging on a freeway, you need the extra time..

When you follow too closely and another driver "cuts" in front of you, the normal reaction is to slam on your brakes and swerve out of the way. Swerving out of the way most often results in cutting someone else off or possibly driving off the roadway. It might also result in the car behind you crashing into you or into other cars around you. If another driver "cuts" in front of you, just take your foot off the gas. This will give you space between your car and the other car, and you can avoid swerving into another lane. Don’t overreact if you are cut off. 

Plan your emergency escape route before
an emergency happens.

Keep A Cushion to the Side

Keep a space cushion on each side of your car.

Don’t drive in the blind spot of another driver. The other driver may not see your car and could change lanes and hit you.
Avoid driving alongside other cars on multilane streets. Someone may crowd your lane or change lanes directly into your car. Move ahead of the other car or drop back.
Keep as much space as you can between yourself and oncoming traffic. On multilane streets, stay out of the lane next to the center line, if you can. That way you will have more room to avoid an oncoming car that suddenly swerves toward you. This is very important at intersections where another driver could turn left without giving a signal. If possible, make room for vehicles entering freeways even though you have the right-of-way.
At freeway exits, don’t drive alongside other cars. A driver on the freeway may pull off suddenly or a driver leaving may swerve back on.
Keep a space between yourself and parked cars. Someone may step out from between them, a car door may open, or a car may start to pull out suddenly.
Be careful when riding near bicycles. A bicycle rider could be seriously hurt in an accident. Always leave plenty of room between your car and any bicycle, and watch carefully for bicycles before turning.
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