Module 3 - COLLISION PREVENTION

The task of driving actually consists of several tasks: controlling the car, watching the road for other drivers and hazards, making sense of signs and signals, and making decisions. What’s more, these also can be broken down further into other tasks. If you find multitasking difficult, you should treat driving in the same way.

Driving defensively is driving to protect yourself while on the road by preparing for and preventing collisions before they occur to you. Safe driving starts with you being able to see where you are going.

Scanning

Baseball Hall of Fame catcher Yogi Berra once said, “You can observe a lot just by watching.” Your vision is perhaps your most important tool for safe driving. How else can you see where you are going or avoid road hazards? We know how important our eyes are to the driving task, yet we still see drivers who fail to look before they change lanes, for example. Fortunately, you can easily avoid these and other hazards for the most part if you develop the habit of constantly scanning the road around you.1

You can use one of several methods to help you scan the road. Some of the more popular include the Smith System and SIPDE, which are discussed below.

The Smith System is a set of five “keys” aimed at making the task of driving safe for you. The five “keys” are:

Aim high in steering. The higher you look, the farther ahead you see. By looking farther ahead, you can see hazards and have time to respond to them. You should look as far ahead as possible in the distance, say about 20-30 seconds ahead. This is about 1-2 blocks in the city at normal, safe speeds and one-third to half a mile on the highway at speeds of up to 65 mph. If you only focus on the car ahead of you, you will not see upcoming hazards in time to react to them safely.

Get the big picture. Scan the entire scene, not just the roadway. This means the sides and behind you as well. You will be able to make better decisions when you are aware of what is going on around you. It is helpful particularly on the open highway and intersections, since danger can come from all sides.

Keep your eyes moving. To scan the entire scene, you need to keep your eyes moving. In addition, conditions on and off the road are constantly changing. Focusing on only one area means you will overlook hazards in others. Check your mirrors and turn your head to check on your blind spots before proceeding with any maneuver.

Leave yourself an out. If you are to get out of a trouble spot, you need an out. Make sure you have an escape route in case of an emergency by maintaining a space cushion around your vehicle. This means keeping the lane next to you clear so you can move there if the car ahead of you stops suddenly, for example. If you are boxed in, you will not be able to avoid another car swerving into you or drive around a hazard in the road.

Make sure others see you. Communicating with other drivers is vital on the road. If you signal your intention to change lanes, for example, other drivers will take note and respond to it. Crashes often occur because one of the drivers failed to see the other vehicle. Always make use of your turn signals and turn on your headlights when it is dark.2

SIPDE is an acronym which stands for the five processes that are central to safe driving according to its creator. Like the Smith System, SIPDE depends on 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:

Search (or Scan) - The first step is to scan the road for potential hazards.

Identify - Next, identify what those hazards are.

Predict - Anticipate how these hazards will affect you.

Decide - Decide how you will act to avoid the hazards.

Execute - Choose a course of action and act on it.2

Another method is commentary driving, which is an advanced driving technique that is also endorsed by many state driver licensing and driver education agencies as a way for parents to help train their teenage drivers. This works by commenting 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 such as the Super Bowl. This helps you focus on your driving as well as anticipate what other drivers will do, making your trip safer.3

When scanning the road, look at least 15-20 seconds ahead (about two blocks in the city or 1/3 mile on the freeway). If you don’t look far enough ahead, you will overlook any hazards that may be coming your way. Also check the vehicles behind you every 5-7 seconds.

Determining an Escape Route

As traffic conditions evolve, you must constantly adjust in order to avoid dangerous situations. However, scanning ahead helps to ensure that your path of travel is safe. This will allow you to spot potential hazards ahead and to adjust your speed or lane position as needed.

Slow down if your view ahead is blocked; you will not be able to adjust otherwise. 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.

As you scan the road, watch for any hazards or indications of them such as brake lights, cars slowing down, lane blockages, and vehicles going significantly faster or slower. Many of these may occur at the same time, so you'll need to be able to predict what may happen. 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.

Minimizing your risks often means making compromises. If there's a long line of cars approaching from the opposite direction, slow down, be prepared to brake, and move to the right. If an approaching vehicle drifts 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.1, 2, 3

Blind Spots

You need to also check your blind spots and avoid lingering in those of other drivers while scanning the road. These are located to the rear at the sides of your vehicle, as represented in the shaded areas in the illustration below. Regardless of the size of other vehicles, you can completely overlook 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.

But your vehicle has some tools to help you with that: the rearview and side mirrors. Check these mirrors about every 5-8 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, they only offer you a limited view, so you 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 ahead should keep you well aware of what occurs around you.4

Your mirrors need to be positioned correctly if you are to check them. When they are correctly positioned, a vehicle’s mirrors will enable you to account for most of your blind spots. Your mirrors must be set from your normal position on the driver’s seat. There should be some overlap 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 have correspondingly 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 look over your shoulder whenever you need to change lanes, turn or back up.5

Backing Up Safely

Blind spots can be a problem when you are backing up. For example, there may be debris to the rear that can damage your car, a passing vehicle, or young children nearby.6

According to KIDS AND CARS, there were 561 reported incidents of children being backed over between 1994 and 2004, with most of them under the age of 4. Of these incidents, 392 resulted in a death, more than 60% involved larger vehicles (i.e. truck, SUV or van), and over 70% were caused by a parent or close relative.7

These researchers found that if your vehicle is longer or taller than average, such as a truck, SUV or van, you have an even bigger blind spot than that of a typical passenger car. They found that a driver of average height (5 feet 8 inches) driving a 2003 Honda Accord EX had a blind spot to the back measuring 13 feet, while a shorter driver (5 feet 1 inch) driving the same car would not be able to see for 23 feet. With the 2003 Dodge Grand Caravan EX (a popular minivan), the average-height driver had a blind spot measuring 14 feet, while it was 23 feet for the shorter driver. However, an average-height driver in a 2004 Ford F-150 XLT had a blind spot of 34 feet, while it was 45 feet for the shorter driver.

It does not really matter how large your vehicle is, as the danger is still there. Always check behind your vehicle before getting in and while you back up. If there are children nearby, make sure you can see them as you back up. You may be better off having someone help while you do the maneuver, especially if you have a large vehicle.8

Florida law says that you may not back up unless you can do so safely and without interfering with traffic. You are also not permitted to back up on a shoulder or anywhere on a limited access roadway such as a freeway.9 Backing up is a maneuver that must be done with care to avoid a collision and perhaps a tragedy. Keep the speed of your vehicle low and look behind you as you back up.6

Following Distance

You’ll be in a better position to avoid crashes if you maintain the proper following distance and have a space cushion around your vehicle. Should the car ahead of you stop abruptly, you'll have one of two choices: stop or change lanes. Scanning ahead will help you know if it is safe for you to move into a lane to your left or right. At higher speeds, you'll need a larger space cushion. This cushion can be determined by following the two-second rule.

This rule allows you to see ahead of the vehicle in front of you and to keep a cushion or safe distance in the event of an emergency or unexpected traffic situation. This is the minimum recommended following distance, though in some circumstances that should be increased. To establish a two-second gap, select a fixed point on the road, such as a sign or tree. Wait for the vehicle ahead of you to pass that point, and then start counting “one-thousand-one, one-thousand-two.” If you pass the fixed point before you finish your count, you are following too closely, so ease off the gas slightly.

A two-second cushion is not enough in certain situations. When that is the case, increase your following distance to at least three seconds, or better yet, four seconds.10 You should widen the gap between your car and the vehicle ahead when:

  • You are being tailgated. Establishing a larger cushion gives you more time to react and brake, thus allowing you to avoid a collision with the vehicle behind you.
  • Your vision of the road is obstructed, or visibility is poor. Increasing the following distance allows you to account for any surprises.
  • You are behind a large vehicle. When you can only see the vehicle’s back in front of you, and not the road, you are too close. To see the road ahead, you need to make room by staying back a bit further.
  • 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. You'll have to avoid hitting the rider, especially if the motorcycle falls.
  • 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.
  • 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 solely on the car in front, or any one thing, but keep your eyes moving. If you see something on the road or in your car, look when it's safe to do so after you check the road ahead.11

How to Avoid the Rear-ender

A rear-end collision is common at intersections, but also may result from tailgating. To avoid being rear-ended by another vehicle, you should do the following:

  • Increase following distance from vehicles in front of you, or leave space ahead of you when stopping at an intersection.
  • Signal to let other drivers know when you plan to make a turn, stop, or change lanes.
  • Brake smoothly by applying gradual pressure. Don’t ride or tap your brakes, as that will only confuse or irritate the driver behind you.
  • Keep pace with traffic whenever possible.
  • Allow tailgaters to pass you by slowing down slightly. Change lanes if needed.
  • Check your mirrors for vehicles behind you. Be aware of the proximity of any that are behind you.
  • Before changing lanes, check to be sure the one you are moving into is clear, and maintain your speed so that vehicles approaching from behind won't have to brake to avoid hitting you.
  • After you stop, keep your foot pressed on the brake pedal to let others know you have stopped. You’ll need to keep your rear lights clean and working.12, 13

Stopping Distance

Do you know how long it takes for you to stop? The speed you travel is a key factor. The greater the speed you travel, the longer it will take for you to stop. But speed is not the only factor that affects stopping distance. On slick roads, such as those you encounter during rain or snow, it will take you longer to stop your vehicle. The same goes if the brakes or tires are worn. No matter how quickly you think you can react, you still need time to respond to a situation and then to stop. 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, and road conditions. The time it takes for your brakes to stop the vehicle are 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 the three distances noted above: 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.14

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, the 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 to apply the brakes, for a total of 293 feet. That's almost the length of a football field! The chart 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
(in feet)
Estimated
Braking Distance
(in feet)
Total Stopping Distance
(in feet)
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

As noted earlier, 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. This will allow you to reduce your reaction time by as much as three-fourths of a second! 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.17

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 the following areas, as drivers ahead of you may see signs of trouble and react to them:

  • Traffic-controlled intersections.
  • Crosswalks.
  • Lanes next to parked cars.
  • Parking lot entrances.
  • Interchanges where vehicles enter and leave.
  • Slippery or ice-covered roads.
  • Where children are present, such as schools, playgrounds or parks.
  • Construction zones.

School Zones

You are required to slow down when nearing a posted school zone where children are present. This means 30 minutes before, during, and 30 minutes after children begin arriving at school (for breakfast or for the start of the school session) and leaving at the end of the school session for the day. At these times, the greatest number of children can be found outside school grounds, but you still should slow down if you see them at other times.18 Chapter 5 discusses these issues further.

Construction Zones

When approaching a construction or maintenance zone, you are required to yield the right-of-way to workers that are present in the area.19 Florida was second to Texas in the number of deaths in these areas in 2006, with 119 people killed.20 It is important to understand that these workers are trying to improve the roads to make your drive in the future better! You must be patient as you travel through a work zone, for the safety of both the workers and yourself. Pay attention to signs that warn you of these zones ahead of time; these are orange in color. The signs are there to protect these workers and you as well. In addition, when driving through these areas:

  • Expect the unexpected. Traffic lanes may have been changed to accommodate the work being done.
  • Slow down. Speeding is a major cause of work zone crashes. Keep in mind that speeding fines are doubled.
  • Don’t tailgate.
  • Maintain a safe distance between your vehicle and the workers and their equipment.
  • Obey flaggers. They wear orange vests or jackets and use red flags or slow/stop signs to direct traffic.
  • Stay alert. Remove distractions that keep your full attention from the roadway. This means putting away your cell phone, leaving your radio alone, etc.
  • Keep up with the flow of traffic. If you need to merge, do it as soon as you can, not at the last minute.
  • Give yourself plenty of time, leaving early if possible. Expect delays. If you check for traffic before you leave, you will be better prepared.21

In General

Always keep the speed of your vehicle under control so that you can scan the road for any hazards, maintain a safe following distance, and stop safely. Maintain control of your vehicle’s speed by covering the brake.


1 Lanier, J. "The Eyes Have It: Visionary Tactics for Smooth, Quick Driving"Inside Line, Edmunds, available at: www.edmunds.com/insideline/do/Features/articleId=104950
2 American Automobile Association, Responsible Driving Chapter 1, Lessons 3, 4. Available at: www.driveraide.com/Pubs/class%20book/Chapter1.htm
3 Institute of Advanced Motorists, "Commentate to Concentrate,"available at: www.irishadvancedmotorists.ie/pressdocs/SafetyTips/Safety_Tips_05-04_Commentate_to_concentrate.pdf
4 Schaller, R. "Defensive Driving Rule #17: Know Your Blind Spots!"RoadTripAmerica.com, available at: www.roadtripamerica.com/DefensiveDriving/Rule17.htm
5 Wren, E. "Setting Outside Mirrors to the Correct Angle,"Drive and Stay Alive, Inc. 2003, available at: www.driveandstayalive.com/articles%20and%20topics/driving-myths-and-mistakes/setting-the-mirrors.htm
6 Schaller, R. "Defensive Driving Rule #19: Avoid Backing Up!"RoadTripAmerica.com, available at: www.roadtripamerica.com/DefensiveDriving/Rule19.htm
7 Kidsandcars.org, "Back Over Fact Sheet,"available at: www.kidsandcars.org/incidents/backover/backoverinformation.html
8 Consumer Reports, "The problem of blind spots,"October 2005, available at: www.consumerreports.org/cro/cars/safety-recalls/mind-that-blind-spot-1005/overview.htm
9 Florida Statute 316.1985
10 Schaller, R. "Defensive Driving Rule #13: Create Space and Use the Two-Seconds-Plus Rule,"RoadTripAmerica.com, available at: www.roadtripamerica.com/DefensiveDriving/Rule13.htm
11 Schaller, R. "Defensive Driving Rule #12: Look Down the Road,"RoadTripAmerica.com, available at: www.roadtripamerica.com/DefensiveDriving/Rule12.htm
12 Schaller, R. "Defensive Driving Rule #51: Make Defensive Stops!"RoadTripAmerica.com, available at: www.roadtripamerica.com/DefensiveDriving/Rule51.htm
13 Schaller, R. "Defensive Driving Rule #27: Get Rid of Tailgaters,"RoadTripAmerica.com, available at: www.roadtripamerica.com/DefensiveDriving/Rule27.htm
14 Memmer, S. and Helperin, J. "Keeping Your (Braking) Distance: More Than Just Slowing Down,"Edmunds.com, November 23, 2000, available at: www.edmunds.com/ownership/driving/articles/43810/article.html
15 NHTSA Highway Safety Programs: Safe & Sober Campaign, "Driving at Night Can Be Deadly,"available at: www.nhtsa.dot.gov/people/outreach/safesobr/pub/deadly.pdf
16 NHTSA, Consumer Braking Information, available at: www.nhtsa.dot.gov/cars/testing/brakes/
17 National Safety Council, "Failure to Yield Right-of-Way,"available at: www.nsc.org/nsm/rightofway.htm
18 Florida Statute 316.1895
19 Florida Statute 316.079
20 Fatalities in Motor Vehicle Traffic Crashes by State and Construction/Maintenance Zone (2006), National Work Zone Safety Information Clearinghouse, available at: wzsafety.tamu.edu/crash_data/workzone_fatalities/2006
21 National Work Zone Awareness Week 2006 Fact Sheet, Federal Highway Administration, available at: safety.fhwa.dot.gov/wz/nwzaw_events/factsheet06.htm


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