Table of Contents

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Defensive Driving

No one likes getting into a collision. It can be quite inconvenient, not to mention expensive. But there is only one guaranteed way to avoid a collision: Sell your vehicle and stay off the road. But for those of us who would rather get out and keep driving our cars, the solution is a bit more complicated. If you want to stay safe on the road, you must always do the following:

  • Obey traffic laws.
  • Drive defensively.
An image of a car's sideview mirror

Collision prevention requires defensive driving and awareness of the environment around your vehicle.

Avoiding crashes is not rocket science. Most collisions involve drivers who fail to do one or both of the above. Think about it - if you are rear-ended on the freeway, it is because the driver who hit you violated the law by following too closely. On the other hand, is it possible that you could have avoided that collision by being more defensive behind the wheel? After all, you were dialing your cell phone when you should have been checking your mirrors. Had you looked, you would have seen that tailgater bearing down on you. You might have had time to change lanes to avoid being hit.

It's simple, right? Not quite!

Once you have mastered the basics, driving becomes "easy." But operating a motor vehicle safely is another matter entirely. Driving safely is a serious challenge. It can be achieved, but it takes commitment and diligence. A driver must be able to multitask behind the wheel without colliding with something, without causing another driver to crash, and last, but not least, without violating traffic laws.

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Perceptual skills needed for driving

Anticipation is an important skill to acquire. Being able to predict a likely outcome is the very essence of defensive driving. When you are behind the wheel, you must think about driving. Forget everything else for the moment - what's missing on your iPod's playlist, etc. - until you are off the road. Various factors affect driver performance, and you must constantly use your perceptual skills for safe driving. They include:

  1. Visual interpretations - If standing still and looking straight ahead, you would be able to see directly in front of you and at an angle to your left and to your right. As speeds increase while driving, our visual field decreases. We need to scan (move the eyes from side to side) to detect possible dangers while driving. The truth is that our most important tool for driving is perhaps our vision.
  2. Hearing - A good sense of hearing is also important while driving. Hearing the sound of an emergency vehicle siren, car horns or trains alerts you of a possible dangerous situation around you. Even if you do not see a car coming towards you or an ambulance coming from behind, your hearing may alert you to their presence before a problem occurs. Your hearing may also alert you of a problem with your car. But while it is not your most important perceptual tool, it can be quite helpful.
  3. Touch - Feeling a vibration in the steering wheel or seat belts tells us of possible mechanical problems.
  4. Smell - The sense of smell is vital in recognizing certain dangerous situations such as: gas, burning, steam or antifreeze leaking.
  5. Reaction abilities - It is important to react quickly when behind the wheel of a motor vehicle. Even a split second can mean the difference between a near miss and a collision. You must be able to quickly respond to unforeseen road hazards, other drivers, and emergencies on the road.
  6. Judging speed and distance - Depth perception helps us to judge the relative distance between two objects. This is important for you as a driver because both depth perception and distance judgment help to control your following distance and adjust your position in traffic.

Defensive driving requires constant decision-making. In every driving situation, the defensive driver must be prepared to stop, slow down, speed up, steer right, steer left, or do nothing. Before you do any actual driving, you may want to practice some of the techniques you learn in this module while riding as a passenger. This will help build your confidence once you actually get behind the wheel.

Video: "Using Your Eyes Effectively"

Safe drivers know how to use their eyes while driving. They rely not just on their central vision when scanning the environment; they use their peripheral (side) vision as well. The following video demonstrates some good techniques for using your vision and where you should concentrate your attention.

Video: "Using Your Eyes Effectively"
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Your vision is one of your most important tools for driving. Your safety may well depend on it! In this chapter, you will learn how to use your senses, particularly your vision, to help you drive safely.

Scanning Techniques

An image of a road

Scanning the road around you will help you easily avoid most hazards.

Baseball Hall of Fame catcher Yogi Berra once said, "You can observe a lot just by watching." As discussed earlier, your most important tool for safe driving is perhaps your vision. How else can you see where you are going? How else can you avoid road hazards? Unfortunately, many of us take our eyesight for granted. How often have you seen people change lanes without looking first? It all comes down to how you use your eyes. Developing the habit of scanning the road around you will help you easily avoid most hazards.

Scanning is a constant visual search of the roadway that surrounds your vehicle. Scanning is not staring. If you look only in one area, you will overlook other potential hazards. You must scan the road, sidewalks, parked cars and the vehicles you are following to anticipate conflicts before they develop into real hazards. Two scanning techniques we will look at are the Smith System and SIPDE.

The Smith System

The Smith System is a set of scanning tasks centered around five "keys," which are:

1. Aim high in steering. When you focus on the road ahead, you need to "aim high," which means looking up ahead into the distance. If you aim low, you would be staring at the rear bumper of the vehicle right in front of you, which is not a good idea. You do need to be aware of that bumper, just don't stare at it. The higher you look, the farther ahead you see. Looking farther ahead allows you to see hazards and conflicts as they develop, which gives you time to respond without being surprised. You should therefore look about 12-15 seconds ahead, which is about 1-2 blocks in the city at normal, safe speeds. If driving on the freeway, you need to look about 20-30 seconds ahead, which is about 1/3 to 1/2 mile at speeds of up to 65 mph. If you only focus on the car in front of you, you will not see upcoming hazards in time to react to them safely.

2. Get the big picture. When you zoom out of an online map, you get a map of a larger area. It's the same idea here. Scan the entire scene (the "big picture"), not just the roadway in front of you. This means the shoulders, the sidewalks and the roadway behind you. You will be able to make better decisions when you are aware of what is going on around you. This is particularly useful on open highways and intersections, where danger can come from all sides.

3. Keep your eyes moving. To "get the big picture," you need to keep your eyes moving. Look far and near and side to side. Remember that conditions on and off the road change constantly. Focusing on only one area means you may overlook hazards in others. Check your mirrors and look over your shoulder to check your blind spots before proceeding with any driving maneuver.

4. Leave yourself an out. If you want to get out of trouble on the road, you need to leave yourself an "out," or an escape route. You will be able to take evasive action only in the direction of an out. Ideally, you should always have four outs: to the front, to the rear, to the left, and to the right. There are many ways you can take evasive action: slam on the brakes (for which you need an out in the rear), accelerate quickly (for which you need an out in the front), and swerve left or right (into your left or right outs). Avoid side-by-side driving, especially on the freeway. If you don't have a space cushion, you will not be able to get around a hazard.

5. Make sure others see you. Crashes often occur because one driver failed to see the other vehicle. Drivers need to communicate with each other for everyone's safety. To make sure they see you, use your:

  • Headlights
  • Taillights
  • Hazard lights
  • Brake lights
  • Horn
  • Hand waves
  • Turn signals

For example, if you signal your intention to change lanes, other drivers will notice and respond to it. Always use your turn signals before turning or changing lanes and turn on your headlights when it is dark. Be sure to avoid driving in the blind spots of other drivers for any length of time.


SIPDE stands for five behaviors that are essential to safe driving. Like the Smith System, SIPDE requires you to use your eyes to be effective. What makes it different from the other method is that anticipation and decision-making also figure as keys in the process. The five steps for SIPDE are:

  1. Search (or Scan) - Scan the road for possible conflicts and hazards.
  2. Identify - Identify what those conflicts and hazards are.
  3. Predict - Anticipate how these conflicts and hazards will affect you.
  4. Decide - Decide how you will act to avoid the conflicts and hazards.
  5. Execute - Choose a course of action and act on it.

The animation below will take you through each step of the SIPDE technique, using a rock slide as an example.

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Observing Your Own Driving

An image of a man driving

Being a "play-by-play commentator" while driving can improve your focus behind the wheel.

Another effective technique that helps newer drivers develop their defensive driving skills is called commentary driving. This is endorsed by many state driver licensing and driver education agencies as a way for parents to help train their teenage drivers. Commentary driving works by commenting aloud on what you see while driving, what actions you are taking and what you can do, which is similar to a play-by-play commentary during a sporting event.

Commentary driving has proven effective for experienced drivers as well, particularly those who have become lazy behind the wheel and need a little spice to stimulate better driving habits. Observations spoken aloud by a driver force him or her to be aware of their silences when they occur, which then force them to react to their gaps in attentiveness.

Following is an example of commentary spoken aloud by a driver:

..."Heading toward the intersection... Car waiting to turn left in front of me... I'm covering the brake... Okay, he's yielding... I'm hitting the gas... Entering the intersection... Scanning left, right and left again... Need to turn right in driveway at the end of the block... Brake lights ahead, slowing down... activating turn signal... Car pulling out... Hit the brake..."

Commentary driving forces drivers to eliminate distractions and focus instead on the driving task as well as refine their ability to anticipate what other drivers will do, making them safer behind the wheel.

Regardless of what technique you use, always look ahead at least 12 seconds (about one to two blocks), or if driving on the freeway, at least 20-30 seconds (1/3 to 1/2 mile on the freeway). If you don't look ahead far enough, you will overlook any hazards that are coming your way. Also check behind you every 5-7 seconds.

Determining an Escape Route

As traffic conditions evolve, you must constantly adjust your speed and lane position in order to avoid danger and keep moving. Scanning ahead allows you to ensure that your path of travel is safe. If it is not, you will have time to make the necessary adjustments such as changing lanes.

Slow Down

Slow down if your view ahead is blocked; you will not be able to adjust otherwise. For example, when you are stuck behind a large truck, your view up ahead will be severely limited. In this situation, you should make a safe lane change as soon as you can. When selecting a lane within traffic clusters to move into, look for gaps wide enough for you to maneuver into without forcing others to slow down.

Watch for Hazards

As you scan the roadway, watch for any hazards or indications of potential conflicts such as road debris, brake lights, lane blockages, and vehicles going significantly faster or slower. On city streets, you should also watch for pedestrians, cyclists, cars pulling out of driveways and parking spaces, car doors opening, and changing traffic signals.

Make Compromises

Minimizing your risks often means making compromises. For example, if there's a long line of cars approaching from the opposite direction on a two-lane highway, you need to slow down, be prepared to brake, and move to the right. Why is this important? One of the drivers may attempt to pass and move into your lane. If an approaching vehicle does move into your lane of travel, slow down and pull over to the right. Sound your horn and flash your lights to warn the driver. When approaching a curve, slow down before entering, and stay toward the right of the lane.

Because several of these events may occur at the same time, you need to be prepared to adjust any maneuver you make to account for all circumstances present. If you spot potential hazards, adjust your speed and lane position to avoid them. Plan possible escape routes by anticipating gaps into which you can move safely to avoid dangerous situations.

Blind Spot Awareness

An image of a car's blind spots

Always check your blind spots when scanning the road.

When scanning the road, you should also check your blind spots. So where are they located? Blind spots are located to the rear of your vehicle at the sides, as shown in the illustration. Regardless of the size of other vehicles, it is possible to be completely unaware of them if they are in your blind spots. Motorcycles are particularly easy to overlook. That is true whether you are an experienced driver or a novice.

Your vehicle has tools to that provide you with a view to your rear: the rear-view and side mirrors. Check these mirrors about every 5-7 seconds and when you plan to change lanes or turn. Traffic conditions change constantly on the road, making this an important habit to acquire. However, mirrors only offer a limited view, so you also need to turn your head over your shoulder for lane changes and turns. Periodically checking your mirrors and glancing over your shoulder as you scan the road should eliminate any surprises in your blind spots and keep you well prepared to take evasive action. Also be sure to avoid lingering in the blind spots of other drivers.

Using Your Mirrors

When your mirrors are correctly positioned, they will enable you to account for most (but not all) of your blind spots. You must set your mirrors from your normal position in the driver's seat. There should be some overlap between the mirrors to account for any obstacles in the rear of your vehicle. For example, taller passengers seated in the rear will block some of your view, as will rear seat head restraints in some vehicles. Larger vehicles (i.e. pickups, minivans, SUVs) have larger blind spots to the rear, making the positioning of your outside mirrors that much more critical. Again, your mirrors can never account for all of your blind spots, so be sure to look over your shoulder whenever you need to change lanes, turn or back up.

Keep Your Distance!

You'll have a better chance to avoid rear-end crashes if you maintain a safe following distance. When you tailgate another vehicle, you are forced to focus on the rear of that vehicle. That prevents you from scanning the road up ahead. If that car ahead of you stops abruptly, you'll have only two choices: stop or change lanes. The recommended minimum following distance for safe driving at speeds of 40 mph or less is three seconds. The three-second rule allows you to scan ahead of the vehicle in front of you and keeps you a safe distance back in case of an emergency or unexpected traffic situation. In certain situations, such as when traveling at higher speeds, you need a greater following distance.

Establishing Following Distance

To establish the three-second gap, first choose a fixed point on the side of the roadway ahead. You want to use something that will not move such as an overpass, sign or tree. Wait for the vehicle ahead to pass the fixed point and then start counting at least two seconds. You can get a relatively accurate count by saying to yourself "one-thousand-one, one-thousand-two, one-thousand-three." If you pass the fixed point before you finish counting, slow down a little because you are too close.

An image depicting following distance

The recommended minimum following distance under 40 mph is three seconds.

In the following situations, you should increase your following distance to at least four seconds, or for an extra margin of safety, five seconds.

  • You are being tailgated. Establishing a larger cushion gives you more time to react and brake, thus helping you to avoid a collision with the vehicle behind you.
  • Your vision of the road is obstructed or visibility in general is poor. Increasing your following distance gives you time to react to any surprises.
  • You are behind a large vehicle, like a truck or bus. When a large vehicle is blocking your view of the road ahead, you must fall back and increase your following distance. The increased distance will allow you to see the road ahead.
  • Driving on slippery roads. It's more difficult to stop due to the reduced traction. You may have to increase the following distance to as much as 10 seconds when driving on icy roads.
  • Following motorcycles. Motorcycles can stop more quickly. Also if the motorcycle crashes, you'll need more distance to avoid hitting the rider.
  • The driver behind you wants to pass. Give him or her space to move into the lane.
  • You see a municipal bus, school bus, or other vehicle that makes frequent stops, such as at railroad crossings.
  • Road or weather conditions are poor. You'll need time to react should something unexpected occurs.
  • Traveling at high speeds. The faster you go, the longer it will take for you to stop.
  • Pulling a trailer or carrying a heavy load. The extra weight makes it more difficult to stop and may pull you in a different direction.
  • Merging onto a freeway. You need to give yourself, and the car you pull in front of, a space cushion.

In order to establish a safe following distance, you need to look ahead and around your vehicle as well as the one ahead of you. Check your mirrors, your speedometer, and the road often. Avoid focusing only on the car in front, or any one thing, but keep your eyes moving. If you need to look at something on the road or in your car, look only when it's safe to do so (and only briefly) after you check the road ahead.

Video: "Managing Space and Time for Safe Driving"

Good drivers are good at managing space and time. This means they constantly make adjustments that keep them safe while driving. This video will demonstrate techniques that safe drivers use to maintain a safe space cushion.

Video: "Managing Space and Time for Safe Driving"
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You can see how maintaining a following distance keeps you safe. You are better able to react to dangerous situations, thus protecting yourself.

Stopping Distance

An image of 'STOP'

Speed, road conditions and vehicle condition all affect how quickly you can stop.

Do you know how long it takes for you to stop? Factors that affect how quickly you can stop include speed, road conditions and vehicle condition. It takes longer than you may think to stop - both in terms of time and distance. Regardless of the conditions or the speed at which you travel, there are always three factors that influence your total stopping distance: perception, reaction time, and braking.

Your perception time is the time it takes for you to see and recognize a hazard. Under ideal conditions (i.e. daytime, dry roads and absence of distractions, measured in a laboratory setting where conditions are controlled), it will take the average driver about three-fourths of a second to perceive the danger. Suppose you are traveling at 40 mph, or about 60 feet per second. By the time you identify a situation, assuming ideal conditions, you will have already traveled about 45 feet. The distance you travel when you perceive a potential danger is your perception distance. Your vision and level of alertness can affect your perception time, as will any distractions.

Once you perceive a hazard on the road, the time it takes you to do something about it is your reaction time. As you react to the danger, you take your foot off the gas and move it on the brake. This usually takes about half a second to three-fourths of a second. At 40 mph, you will have traveled 30 to 45 feet. The distance you travel as you react to the potential danger is your reaction distance.

Your braking distance is the distance it takes for your vehicle to stop after you press the brake pedal. This will be affected by the condition of your brakes, your tires, the weight of your vehicle, road surface and road grade. Your braking time is also dependent on these factors. At 40 mph, it may take your vehicle about 72 feet to stop after you apply the brakes. When you double your speed, the braking distance is typically about four times longer. However, this is not your total stopping distance.

Your vehicle's total stopping distance is the sum of perception distance, reaction distance, and braking distance. When traveling at 40 mph, supposing a total perception and reaction time of 1.5 seconds, you will have traveled about 160 feet before finally coming to a stop.

The average driver in a passenger car traveling at 20 mph in ideal conditions will need approximately 44 feet to perceive and react to a situation, then 18 feet to apply the brakes, for a total stopping distance of 62 feet. However, time and distance needs increase considerably at higher speeds. At 60 mph, it will take about 132 feet to perceive and react, then 161 feet for the brakes to stop the vehicle, for a total of 293 feet. That's almost the length of a football field!

The table below shows the approximate total distance it will take to stop from various speeds (again, distances are approximate and assume ideal laboratory conditions):

Speed (in mph) Perception + Reaction Distance Estimated Braking Distance Total Stopping Distance
20 mph 44 feet 18 feet 62 feet
30 mph 66 feet 40 feet 106 feet
40 mph 88 feet 72 feet 160 feet
50 mph 110 feet 112 feet 222 feet
60 mph 132 feet 161 feet 293 feet
70 mph 154 feet 220 feet 374 feet

When adverse conditions are factored in, it will take much longer to stop. One technique that will help you reduce your stopping distance - by cutting down on your reaction time - is covering the brake.

An image of a foot ready to hit the brake

Covering the brake allows you to react to hazardous situations more quickly.

Sometimes you need to be prepared to stop right away, and the best way is to cover your brake. Covering the brake means placing your foot over the brake but without touching it until needed. This allows you to respond more quickly to hazardous situations, and it may reduce your reaction time by as much as three-fourths of a second. So when should you cover your brakes? You should use this technique when:

  • You are driving next to parked cars.
  • You are approaching intersections.
  • You are approaching traffic signals.
  • You are driving in a school zone.
  • You are seeing brake lights of other cars.

Riding the brake (keeping your foot pressed down on the brake slightly) causes more wear and tear on your vehicle and gives other drivers the false impression that you are about to stop. In contrast, covering the brake is often prudent and is a safe driving practice. Of course you cannot do this continuously while you drive, but when you approach potentially hazardous areas such as intersections, covering the brake is a good idea.

Put Your Knowledge to the Test

As a driver, you must constantly perceive road hazards and take the appropriate actions. The laws of physics apply whenever and wherever you drive. Put yourself behind the wheel in the following animated scenario and test your skills. Remember, you must decide if and when to take action.

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How did you do? Threats on the road often come from unexpected places. Whether it's another vehicle running a red light or an animal crossing the road, you must always be prepared. The laws of physics cannot be broken.

Be a Defensive Driver

To sum it up, defensive driving requires you to do the following:

Adjusting Your Speed

As you scan the road for changes in traffic conditions, you will often need to adjust your speed accordingly. Prepare to slow down or stop when you approach these areas:

An image of three cars stopped at an intersection

Be prepared to slow down or stop when you approach intersections or crosswalks.

  • Intersections.
  • Crosswalks.
  • Lanes next to parked cars.
  • Parking lot entrances.
  • Freeway interchanges where vehicles enter and leave.
  • Slippery or ice-covered roads.
  • Schools, playgrounds, parks or any other place where children are present.
  • Construction zones.

Anticipating the Actions of Others

You can steer clear of bad drivers by properly positioning your vehicle and having general road awareness. Avoid making assumptions that other drivers will complete certain maneuvers simply because it may appear that way. Never attempt to force your way into traffic. Anticipation of other drivers' actions, in combination with yielding the right-of- way, is important. Forfeiting the right-of-way to other drivers prevents collisions. Some things to remember include:

  • Always expect the unexpected.
  • Keep your eyes moving, and always be aware of everything that's going on around you.
  • When someone passes you, assume he/she will pull in front of you and then slow down; it's nice to be pleasantly surprised if he/she does not.
  • Check your rear view mirror every five to seven seconds.
  • If you see someone getting into his/her car, assume that the driver will pull out into the street in front of you without looking.

You have to, in effect, drive for everyone around you, not just for yourself.

Driving Defensively

To avoid being in a traffic incident because of someone else's mistake, you must drive defensively. To be a defensive driver, you must:

  • Keep your eyes moving. Be aware of what is happening on the sides of the road, and check your mirrors every few seconds.
  • Be prepared for other drivers to make mistakes, and think of what you would do if a mistake does happen.
  • Avoid relying on traffic signs or signals to keep others from crossing in front of you. Drivers do not always obey traffic signals.
  • Always look left, right, and then left again at an intersection, even if opposing traffic has a red light or stop sign.