DRIVER EDUCATION
STUDENT LEARNING PLAN #7
THE EVALUATION OF HTS
SITUATIONS AND HAZARDS
After identifying an HTS hazard, the driver will need to predict what will happen. Is there a good chance for a collision? To make predictions call for the ability to make judgements and evaluations. The evaluation of complex traffic situations is one of the most difficult things a driver must learn. These lessons will provide you with the know-how and practice to evaluate hazards in time to avoid them.
DEMONSTRATION CENTER PROJECT
MAIN IDEA
Driving an automobile involves the evaluation of HTS situations for those highway and traffic hazards that could affect the driver’s intended path of travel.
SUPPORTING IDEAS
1. Drivers run into highway hazards because they are forced to leave their intended path of travel.
2. Improper evaluation of highway conditions can cause a driver to leave his or her intended path of travel.
3. Traffic hazards are evaluated as to where and when they would probably conflict with the driver’s intended path of travel.
4. The probable actions of other users is judged by the evidence for or against such action taking place.
LESSON IDEAS
Drivers run into highway hazards because they are forced to leave their intended path of travel.
Improper evaluation of highway conditions can cause a driver to leave the intended path of travel.
LESSON OBJECTIVES
1. For a given HTS situation in which a vehicle is coming to an area of reduced traction, you can judge and tell—
- how much the traction would be reduced;
- if there is a good chance for a loss of vehicle control at the given speed;
- how the probable loss of vehicle control would change the vehicle direction and speed’
- if there is a good chance that vehicle will run into a nearby highway hazard unless proper adjustments in speed and direction are made.
2. For a given HTS situation in which a vehicle is coming to an area of limited visibility, you can judge and tell—
- if the sight distance ahead will be less than the four-second stopping zone for the given vehicle speed;
- if the vehicle’s four-second stopping distance from the intersection is less or greater than the distance observed down an uncontrolled side road.
- the kind of hazards to expect in the hidden area of the roadway(s).
3. For a given HTS situation in which a vehicle is coming to an area of reduced space, you can judge and tell—
- if reduced traction or visibility would increase the chance of running into a nearby hazard;
- if there is enough space for correction any expected errors when making maneuvers.
LEARNING ACTIVITIES
Required activities will be assigned by your teacher at a time when your schedule permits. The others are optional.
1. Read and discuss the first eleven pages of “The Evaluation of HTS Events” Review readings on natural laws and skidding causes.
2. Observe films in the classroom or simulator laboratory and discuss the probable effects of the reduced traction, visibility and space areas on driver controls.
3. As a driver or observer in the driver education car, practice evaluating roadway conditions twelve seconds ahead of car. Compare your judgments with those of your classmates.
4. Make a survey of the highway conditions in your community. Develop a lost of those locations with problem situations that have led or could lead to collisions.
LESSON IDEAS
Traffic hazards are evaluated as to where and when they would probably conflict with the driver’s intended path of travel.
The probable actions of other users is judged by the evidence for or against such
action taking place.
LESSON OBJECTIVES
1. For each of these situations, you can describe which of the possible actions a driver or pedestrian can make that will lead to a probable closing of your intended path of travel:
a. oncoming car situations
b. ongoing or cars ahead situations
c. following car situations
d. entering and merging car situations
e. intersecting cars and pedestrian situations
2. For a traffic hazard in a given HTS situation, you can predict and tell—
a. if there is a good chance the traffic controls will not be obeyed;
b. what effect the road conditions will likely have on control actions;
c. what are the probable errors;
d. if there is a good chance a specific error will be made.
3. For a given HTS situation, you can predict and tell if a traffic hazard has a high or low probability for closing on your intended path of travel.
4. For a given traffic hazard with high closing probability, you can predict and tell—
Where and when the closing will take place in your path of travel.
LEARNING ACTIVITIES
Required activities will be assigned by your teacher at a time when your schedule permits.
1. Read and discuss the part on how to evaluate traffic hazards in “The Evaluation of HTS Events.” Review the section on elements and clues to look for in the “Identification of HTS Elements and Clues.”
2. Write out the answers to the “Case Study Traffic Situations.” Diagrams and instruction sheets will be provided by your teacher. Draw a diagram of at least one traffic situation problem that you have observed in your community or on a trip.
3. As a observer or driver in the driver education car, use commentary driving and checklists to: (a) indicate whether or not the twelve-second path of travel is clear or not clear, (b) predict where and when a traffic hazard will close on your intended path of travel, and (c) support your predictions with evidence when time is made available.
4. Practice the evaluation and prediction of traffic hazard movements when riding with your parents, relatives, or friends.
THE EVLAUATION OF HTS EVENTS
Illinois Demonstration Center Project
A competent driver has the ability to select a safe path of travel that is free from hazards at the time when a driver will want to use such a pathway. It is a pathway that has enough clear space for driving a car along it. When there is not enough clear space ahead of a car, then there is a chance for a collision.
You have already learned how to identify HTS hazards and clues related to them. This is the first step toward selecting a safe path of travel. Now, you will need to learn how to predict what the identified hazards will do. Will they move into your selected pathway at a time you had planned to be there?
To make predictions about HTS events and hazards, a driver will need to use his/her higher mental abilities to make sound judgments. This involves thinking about information perceived from the HTS scene along with related information already stored in the mind. We shall call such a mental ability evaluation.
THE THREE PARTS OF THE INTENDED PATH OF TRAVEL
The evaluation of HTS events is for the purpose of deciding whether or not the driver has a clear path of travel. Therefore, let’s review the parts of a driver’s intended path of travel. The competent driver should visualize the path of travel as made up of three parts. These parts are: (1) the two-second following distance, (2) the four second stopping zone, and (3) the twelve second travel path.
THE TWO-SECOND FOLLOWING DISTANCE is that part of the intended path of travel which extends a distance of two seconds in front of the driver’s vehicle. It is that distance or space interval you should follow behind an ongoing vehicle. Since an ongoing car is moving about the same speed you are, this distance provides you with adequate space for stopping visibility. Since this distance varies with the speed of cars, it is appropriate for normal driving speeds under normal roadway conditions. Of course, when traction is reduced, the time should be increased to three or more seconds.
THE FOUR-SECOND STOPPING ZONE is
That part of the intended path of travel that extends
a distance of four seconds in front of the driver’s vehicle. It is that minimum distance you will usually need to stop for a fixed object in the roadway or for other traffic moving across your path of travel. This could be an intersecting or entering car, a pedestrian, or an animal. It should
be obvious that you should never allow a hazard to move into or remain in the four-second stopping zone. Otherwise a collision would be most difficult to avoid.
THE TWELVE-SECOND TRAVEL PATH is the distance that extends a total of twelve seconds ahead of your vehicle along the intended path of travel. This should usually be considered the minimum sight distance you need ahead of your car. Under ordinary conditions, this should give you time to identify, evaluate and decide what to do about a hazard before your four-second stopping zone is reached.
There will be situations, such as bumper to bumper rush hour traffic, when these timed distances may not be practical. However, they should be goals that a driver should always strive for.
Now that we have looked at each part of the intended path of travel, it should be easier to understand why we usually think of distance in terms of time. Timing is extremely important for avoiding HTS hazards. Time is easier and more accurate to estimate than distance. Also, you have better control over time because of your ability to control the speed and placement of your car.
GENERAL GUIDES FOR THE EVLUATION OF HTS HAZARDS
If HTS hazards are to be avoided, the driver must make evaluations in time to take some action. Each driver will need a systematic pattern of thinking for making wise evaluations. The following guides should be helpful.
1. EVAALUATE HAZARDS IN ADVANCE OF FOUR SECOND
STOPPING ZONE
A driver should always get in the habit of evaluating hazards as far in advance of his/her four-second stopping zone as practical. A driver should be especially alert for unusual highway or traffic conditions.
A sudden change in an unfamiliar roadway or disabled car can be a surprise to a driver. The more unusual or complex the events, the more time will be required for evaluation.
One way a driver can avoid collisions is to prevent becoming surprised. Drivers who anticipate trouble early enough stay out of collisions. They give themselves enough time to make proper adjustments. The answer to surprise is awareness and anticipation.
2. JUDGE THE HAZARDS FOR THEIR CLOSING PROBABILITIES
The evaluation of HTS hazards has to do mostly with traffic movement. The driver will want to judge whether or not some movement will take place that will lead to a conflict or collision. THE LIKELIHOOD OR CHANCE FOR YOUR VEHICLE AND A HAZARD TO MOVE CLOSER TOGETHER AS YOU FOLLOW YOUR PATH OF TRAVEL WILL BE CALLED CLOSING PROBABILITY. Our evaluation as a driver is to determine whether or not there is a good chance or probability for a closing movement to take place. Will the other driver or pedestrian make the move that will cause the distance between us to decrease?
What is the best way to judge closing probabilities? To make judgments requires the collection of evidence (clues) that must be thought of in terms of effect. What will it do? And how much will it do? Then we will have a basis for making predictions.
Therefore, the probability for closing with a HTS hazard must be judged in terms of the available evidence for of against the closing to take place. In some cases the amount of evidence noted may not always be as important as the kind or quality of evidence.
An HTS HAZZRD WITH LOW CLOSING PROBABILITY IS ONE FOR WHICH VERY LITTLE IF ANY EVIDENCE IS AVAILABLE FOR A CLOSING TO TAKE PLACE. Usually there is strong evidence against the closing to happen. A pedestrian walking toward a house or parked cars with no drivers would be good examples. Those hazards with low probability for closing on your path of travel can be dismissed from your thinking as unimportant.
An HTS HAZARD WITH HIGH CLOSING PROBABILITY IS ONE FOR WHICH THERE IS CLEARLY MORE EVIDENCE FOR THE CLOSING TO TAKE PLACE THAN THERE IS AGAINST SUCH CLOSING. If there is some doubt as to whether closing will take place, it is usually safest to assume the worst and predict a closing on the path of travel. Driver should continue to look for additional or new evidence of a closing movement.
3. PREDICT WHEN AND WHERE THE CLOSING WITH A HAZARD WILL PROBABLY TAKE PLACE
Once you have predicted a high probability for closing, you will then need to predict where and when such closing would most likely happen. This can be done with the evidence used for judging the closing movements.
For a hazard to cause a conflict or lead to a collision, it must be in your path of travel at the same time you are. This means you should be concerned first with those hazards that could come into or stay in your twelve-second path of travel.
Here are two examples: A small child is walking or running toward the street. There definitely could be closure on your path of travel. But you judge the child could not reach the street until after you have driven by. In another situation, you judge an intersecting car will cross your path of travel about twelve seconds away. In either situation you would not be faced with conflict. You would have a clear and safe path of travel.
1. EVALUATED HAZARDS IN ADVANCE OF FOUR-SECOND ZONE.
2. JUDGE HAZARDS FOR CLOSING PROBABILITIES.
3. PREDICT WHERE AND WHEN CLOSING WILL HAPPEN.
HOW TO EVALUATE HIGHWAY HAZARDS
There are two major types of HTS hazards—traffic and highway. Generally a driver will have to deal with both types of hazards together. However, there is an increasing number of single vehicle collisions that do not involve other traffic. It will be less complicated to learn first how to evaluate highway hazards.
We have defined a highway hazard as an object, structure, or part of the highway environment with which you could collide. Examples are poles, guardrails, and bridge structures. A high curbing or deep hole in the roadway would be classified as a hazard only if it could cause damage to your car or you. Wet leaves on the roadway surface are not considered a highway hazard because they cannot collide with you car.
We use the term “highway rather than roadway to agree with the definitions used by traffic engineers. According to their definition, a highway includes the roadway, shoulders, medians, and all other areas between the boundary lines “right-of-way.”
Most highway hazards, then, are fixed objects along the roadway. A barricade or a rock slide would be an exception. No driver would select an intended path of travel with a highway hazard in it. Therefore, it is only as a driver leaves the intended path of travel that there would be a good probability for closing with a highway hazard.
Why should there be an increasing number of single vehicle collisions with highway hazards? There are three reasons. First is driver condition such as a driver who is sleepy, drugged, or inexperienced. The second is vehicle condition such as a tire blow out or steering failure. The third is highway condition, which we are interested in here.
There are three main areas of the highway condition that are factors in causing a driver to have a collision. These are (1) areas of reduced traction, (2) areas of reduced visibility, and (3)areas of reduced space. They will need careful evaluation by drivers.
1. HOW TO EVALUATE AREAS OF REDUCED TRACTIONS
Areas of reduced traction must be evaluated because of their effect on car control. Reduced traction always increases the possibility of skidding. A skidding car can change direction, speed or both. As a result, the car may be forced from its intended pathway into a highway hazard.
When a driver evaluates areas of reduced traction, he/she will need to judge theamount of reduced traction, the effect on car control, and the probability for the car running into a nearby hazard. Then the driver can either avoid or adjust to the conditions.
HOW MUCH WILL THE TRACTION BE REDUCED? The amount of traction varies with the road surface. Holes, bumps and cracks can cause control problems. A wet brick pavement usually provides less traction than a wet concrete surface. The car will be harder to control on an ice covered roadway that is crowned than one that is flat. Water mixed with oil or dirt is more slippery than a clean surface. The depth of water can affect the tendency for a car to hydroplane.
The weather conditions around the area can also affect the amount of traction. The temperature or changes in temperature can affect the slipperiness of ice or packed snow. Surfaces of bridges and overpasses will freeze quicker and take longer to melt. So will shaded areas. Wind gusts and strong crosswinds can make steering more difficult on a slippery surface.
HOW WILL THE AREA AFFECT CAR CONTROL? Steering straigth ahead over patches of ice or wet leaves creates unequal traction and possible fishtailing. Any condition that will cause the car to skid sideways can result in leaving the intended path. The increase in the braking distance will also need to be estimated.
The chance for a collision will depend on the amount of control the driver may lose and the location of the hazard or hazards. The more trees and the closer they are to the highway, the more the chance for a skidding car to hit them.
Whether or not a certain maneuver is planned or required can also increase the chance for driver error. Lane changing or cornering on a slippery surface can lead to skidding sideways. Accelerating on upgrades and braking on downgrades can easily lead to loss to control.
2. HOW TO EVALUATE AREAS OF REDUCED VISIBILITY
Areas of reduced visibility may be due to weather conditions, kind and location of traffic, conditions within your car, and conditions of the highway. In this section we will be concerned mostly with highway conditions.
HOW DOES THE STOPPING ZONE COMPARE WITH THE SIGHT DISTANCE? Highway and traffic conditions can very easily reduce a driver’s sight distance and visual lead time. This could result in a fixed or slow moving hazard being hidden from view until too late. For example, hillcrests or curves could hide a disabled car or a slow moving farm vehicle. A large truck or bus can also reduce the view of your pathway. This is especially true when the truck is stopped to make a left turn. Of course small compact cars and motorcycles are easily hidden from view by larger vehicle or dips in the roadway.
HOW DOES THE STOPPING ZONE COMPARE WITH THE FIELD OF VIEW? Highway conditions also reduce your field of view to either side of your intended path of travel. Hedges, signs, buildings and parked vehicles may block your view at intersections and private driveways. Not only is you ability to see moving hazards reduced, but the drivers of intersecting vehicles can’t see you. These situations are especially dangerous, since it may be possible for the hidden hazards to move into your four-second stopping zone.
WHAT KIND OF HAZARD AND MOVEMENT CAN BE EXPECTED?
The clues relating to the direction and rate of movement of a hazard are usually hidden along with the hazard. To help evaluate, a driver should think of the setting for the area and such factors as time of day and season of the year. For example, during planting and harvesting seasons in rural areas, a driver should expect various types of farm vehicles to be using the highways. School buses can be expected at certain times during the day. Mailboxes, telephone lines and clouds of dust could serve as clues to the possible presence of other vehicles, animals, or pedestrians.
3. HOW TO EVALUATE AREAS OF REDUCED SPACE
Areas of reduced space are areas in which the driver will have very little space on either side of the car. Frequently there is only one narrow path of travel available. This means that braking may be the only control action that can be used for avoiding a hazard.
IS THERE REDUCED TRACTION OR VISIBILITY IN THE AREA?
The combination of poor traction and limited space can be hard to judge. Only a slight side skid is enough to throw a car into a nearby object. Many areas have reduced space because of roadside structures which also limit visibility. Bridges, hillcrests and underpasses are good examples.
WILL CHANGES IN DIRECTION BE REQUIRED IN THE AREA?
In such areas, there is little room for correcting steering errors or speed adjustments errors. Many areas of reduced space require lane changes. This means the car may be going into a situation at an angle. Turning into a narrow driveway or onto a narrow gravel side road from a busy highway can cause spacing problems.
HOW TO EVALUATE HIGHWAY HAZARDS EVALUATE AREAS OF REDUCED TRACTION
How much traction is reduced?
How will area affect car control?
What are changes for hitting a hazard?
EVALUATE AREAS OF REDUCED VISIBILITY
Comparing stopping zone with sight distance.
Compare stopping zone with field of view.
Expect movement from area.
EVALUATE AREAS OF REDUCED SPACE
Is there reduced traction or visibility in area?
Will changes in direction be required?
QUESTIONS FOR REVIEW
1. How can you prevent becoming surprised when driving?
2. Why is it best to think of distance in terms of time?
3. What is the four-second stopping zone?
4. How do you decide whether a hazard has high or low closing probability?
5. How would you go about evaluating (a) areas of reduced traction, (b) areas of reduced visibility, and (c) areas of reduced space?
HOW TO EVALUATE TRAFFIC HAZARDS
Evaluating traffic hazards is probably the most difficult and important thing a driver must do. Other users might be traveling at high speeds and make sudden changes in direction. There are so many possibilities that can happen in complex system. It is not always easy to estimate the space and time between two or more moving vehicles. There is always the need to predict the actions of drivers and pedestrians who are around you. At times this can be a real problem.
Drivers can do become very successful in evaluating traffic hazards an avoiding collisions. They do this by learning the knowledge and mental processes required. When common rules are known and followed, then drivers can make good predictions about the actions of their users. Even when such rules are not followed, drivers can know the kind of errors that are usually made in various situations.
You can do a good job of evaluating hazards if you learn what to do and how to do it. You must be willing to practice over and over. First you must be able to apply most of the knowledge and experience you have gained thus far. Then you will need to develop an efficient set of thought patterns. The following guided are provided to help you in this development.
1. KNOW HOW TRAFFIC COLLISIONS HAPPEN
Drivers need to be aware of how collisions happen. Then they can do a better job of selecting where to look and what to expect. Most cars and pedestrians will become a conflict by entering your path of travel from the front, the rear or the sides. The majority of collisions are a result of traffic moving from the sides.
There are five types of conflict situations you should know about and be able to evaluate.
ONCOMING CAR SITUATIONS—oncoming cars may cross the center line and come into your intended path of travel. Even on freeways, cars have been known to cross the median or jump the guardrails and end up on front of other car. The head-on crashes that result are the most dangerous of all.
ONGOING OR CARS AHEAD SITUATIONS—ongoing cars can do two things that can cause you a problem. A driver of the car ahead can stop suddenly, or swerve out of his/her lane to avoid hitting another car or object in the roadway. In either case a collision could easily result.
FOLLOWING CAR SITUATIONS- – a following car could crash into your rear end if you suddenly stop. Other drivers who tailgate always create a serious problem, especially at night.
ENTERING AND MERGING CAR SITUATIONS- – in these situations, cars will come into your path or travel at a slight angle from either side. They are actually changing lanes. Such cars are usually accelerating from either a standing or moving position. A driver can expect these cars to enter his/her pathway from a parked position along a street or a shoulder of the highway. On freeways one can expect merging cars from ramps and acceleration lanes. Passing cars on two lane highways are also included in this type of situation.
INTERSECTING CARS AND PEDESTRIANS SITUATIONS- -Except for controlled-access highways, most roadways meet or cross other roadways and private driveways to form various types of intersections. These intersecting situations make it possible for cars and pedestrians to cross another driver’s pathway at or about right angles. Of course cars can cross a drivers pathway at various angles by turning into or from such intersecting roads.
It should be obvious that intersecting traffic creates serious hazards. In spite of the many traffic control devices, these locations account for more than one-fourth of all the collisions.
2. KNOW WHY TRAFFIC COLLISIONS HAPPEN
Very few collisions happen that don’t involve a human error. Not all human errors can be eliminated. We will all make mistakes from time to time. However, it is our responsibility to make as few errors as possible. We will make fewer driving errors and avoid the errors of other road users if we know what errors to expect. Following are examples of errors you can learn to expect and protect yourself against.
MAKES SEEING ERRORS.
… Allows vision to be blocked due to ice, snow, dirt, packages, and clothes covering windows.
… Becomes inattentive or distracted due to mental problems, watching advertising signs or scenic views, visiting with passengers, smoking, eating, and map reading.
… Does not try to get eye contact with others.
… Runs red light; jumps green light.
… Does not yield to car on right.
FAILS TO ADJUST SPEED FOR CONDITIONS.
… Approaches stop or yield sign too fast.
… Takes corners too fast.
… Does not adjust speed for areas of reduced traction.
MISJUDGES DISTANCE OR SPACE REQUIREMENTS.
… Tailgates other vehicles
… Swings wide or cuts turns.
… Improper passing and overtaking.
… Leaving or entering parking spots.
… Improper lane selection or position for turns.
MAKES IMPROPER CAR CONTROLS
… Brakes or steers too quickly on slippery pavement.
… Poor recovery after running off pavement.
… Motorcyclist uses improper body lean.
FAILS TO SIGNAL INTENTIONS PROPERLY.
… No signal when changing directions
… Improper use of parking or flasher lights.
… Gives false signal.
SWERVES OR STOPS SUDDENLY TO AVOID OTHER USERS.
… Avoids entering or parking vehicles.
… Avoids pedestrians or bicyclist.
… Avoids slow moving vehicles such as farm tractor.
… Avoids driver who can’t complete maneuver.
3. EVALUATE THE EVIDENCE FOR AND AGAINST THE OTHER USER ACTION THAT WOULD LEAD TO A HIGH CLOSING PROBABILITY.
There is an endless variety of events and situations that take place as a driver moves along the roadway. From our experience with identification, we know there will be more HTS events and clues to evaluate than we will have time for. Therefore, we must be selective in our evaluation of the evidence for and against closing movements. Here are guides that can help a driver be selective and make the best use of the time available.
IDENTIFY WHICH ACTION THE OTHER USER MUST TALE TO CLOSE ON THE PATH OF TRAVEL. – -Fortunately, there are few possible actions that each driver or pedestrian can take. A driver of a moving car can (1) increase or decrease speed, (2) change directions to the right, (3) or left, (4) or continue the same speed. The parked car driver cannot decrease speed, but can back up. A combination of speed and directional changes is also possible.
In most situations, only one of these other user actions could cause a driver to close on your path of travel. In the case of an oncoming car, you must judge whether or not the driver will turn into your path. For the ongoing car, you will need to judge whether the driver will decrease speed and perhaps break suddenly. Will the intersecting car choose a speed that will get it into the intersection at the same time I will get there? Will the following car be able to reduce speed when I do? Will the car along the roadway accelerate into my path?
A key question is, what action will the other user have to take that will cause the distance between us to be reduced? This simplifies our job of evaluation. We only have to look for our evidence of the one action rather than several possibilities.
JUDGE WHAT EFFECT TRAFFIC CONTROLS WILL HAVE ON THE OTHER USER ACTIONS. When rules of the road are known and followed, driver actions are usually easy to predict. It can be assumed that a vehicle coming to a stop sign will stop. Evaluations can then be limited to those clues that can be used to identify the other users who do not follow these rules.
JUDGE WHAT EFFECT HIGHWAY CONDITIONS WILL HAVE ON THE OTHER USER ACTION. You have already learned how to evaluate the effect that certain highway conditions can have on your own car control. Now you will need to judge what other users are likely to do when faced with areas of reduced traction, reduced visibility and reduced space. Are there clues the other user may lose control? Will the other user be forced into your path of travel?
JUDGE THE PROBABILITY FOR A DRIVER OR PEDESTRIAN ERROR IN EACH SITUATION. Once you have learned what errors to expect, you can be more selective in what to look for. Most errors involve speed control and right-of-way problems. This is probably because most of us find judging space and time hard to do. The more practice and experience you have with such judgements in your own driving, the better you can evaluate other driver judgements.
For the maneuvers other drives are attempting , you might ask yourself: How much time and space will be needed? What procedures should be followed? Will the driver be able to complete the maneuver?
PREDICT WHICH TRAFFIC HAZARDDS HAVE A HIGH CLOSING PROBABILITY. The line of reasoning used above should give you enough evidence for making a final prediction. Situations can become complicated because of the interaction of two or more hazards. In the case of an oncoming car, suppose the car stops suddenly. The second or third car following may swerve into your path. This means you must constantly evaluate the whole traffic scene around you for the various traffic interactions which could affect you.
4. PREDICT WHERE AND WHEN THE PROBABLE CLOSING WILL TAKE PLACE
Traffic collisions happen because at least two persons try to use the same space in a highway at the same time. These collisions can be avoided if the point of conflict is identified soon enough and one or both persons make the proper changes in direction or speed or both. An evaluation of how much and how fast the other user is closing is required for predicting points of conflict.
HOW MUCH OF THE DRIVER’S INTENDED PATH OF TRAVEL WILL BE USED BY A TRAFFIC HAZARD? Some traffic hazards may use all the path of travel; others may use only use a part. A parallel parking car may swing into part of the next lane. Pedestrians, bicyclists, and motorcyclists very seldom take up more than a part of a standard lane width. On going cars that are turning left or right may not complete the turn. A disabled car may still be part of the roadway. Some of these situations may be difficult to judge. To many drivers may be tempted to squeeze by.
WILL THE TRAFFIC HAZARD COME INTO OR BE IN THE TWELVE-SECOND PATH OF TRAVEL? How fast a traffic hazard is closing on your path of travel will dtermine when it reaches you. There is also the possibility of an increase or decrease in this speed. The evidence being evaluated for and against closing can also be used for this final judgement.
HOW TO EVALUATE TRAFFIC HAZARDS
1. Know How Traffic Collisions Happen
a. Oncoming car situations
b. Ongoing or cars ahead situations
c. Following car situations’
d. Entering and merging car situations
e. Intersecting car and pedestrian situations
2. Know Why Traffic Collisions Happen
a. Makes seeing errors
b. Fails to yield right-of-way
c. Fails to adjust speed for conditions
d. Misjudges distance or space requirements
e. Makes improper car control actions
f. Fails to signal intentions properly
g. Swerves or stops suddenly to avoid other users
3. Evaluate the Evidence For and Against the Other User Actions That Would Lead to a High Closing Probability
a. Identify the action the other user must take to close in the path of travel.
b. Judge what effect traffic controls will have on the other user actions
c. Judge what effect the highway conditions will have on the other user action
d. Judge the probability for a driver or pedestrian error in each situation
e. Predict which traffic hazards have a high closing probability
4. Predict where and when the Probable Closing will take Place
a. How much of the pathway will the traffic hazard use?
b. Will the traffic hazard come into or be on the twelve second path of travel?
SOME AFTER THOUGHTS
Up to now you may have found some of these ideas and guides for evaluation interesting. But you may also be thinking to yourself. “Who on the world would have time for all of that while driving? It’s a bit unreal.” And your right! However, let’s not forget the power of the human brain.
The human brain is like a giant computer. It can do many amazing things. With practice, some of these things may take only a fraction of a second. But our brain, like a computer, is a little value if it hasn’t been fed the right kind of information. It will also need some rules or guides for using the incoming and stored information. This is what we are trying to do.
At one time or another, you have probably worked on a puzzle. After you have once solved a puzzle, what happen the second tine your try it? It then becomes very easy and takes only a fraction of the time you first needed. This is because you can quickly identify the clues and know what to expect. You no longer have to rely on trial and error methods. Other similar puzzles become easier to work the first time you try them, This is also true of traffic situations.
Once you evaluate traffic situations in class or in a car, predicting the actions of others becomes easy. With practice, you will be able to handle the common situations almost automatically. This frees the higher centers of your mind for dealing with the unusual or complex traffic situations. Then you will have a good chance of never getting trapped into a collision course.
Another interesting thing will begin to happen. Your mind will bring together all you have learned into one whole process. Your visual habits, identification, and evaluation abilities, along with your stored information will combine into set of mental actions. As you scan the HTS scene, you can identify and evaluate the hazards and their clues at the same time. You can then build up your confidence and sense of pride in your ability to drive without ever having a preventable collision.
QUESTIONS FOR REVIEW
1. How do collisions happen?
2. What ate some of the common errors you can expect of other drivers and pedestrians?
3. For situations involving (a) oncoming cars, (b) following cars, (c) ongoing cars and (d) entering cars, what other driver action will cause a probable closing or collision?
4. How would you go about predicting when and where a probable closing or collision could take place with your car and another car?
5. How can you learn to make predictions quickly while driving?
DEFINITIONS OF TERMS
CLOSING POTENTIAL—is the possibility that your vehicle and HTS hazard may move closer together.
CLOSING PROBABILITY—is the likelihood or chance that your vehicle and an HTS hazard will move closer together.
a. Low closing probability for an HTS hazard is one for which very little if any evidence is available for a closing movement to take place.
b. High closing probability for an HTS hazard is one for which there is clearly more evidence for a closing movement to take place than there is against such closing.
EVALUTATION—involves the making of judgements about the value or worth of something. In driving, we are interested in the amount and importance of some HTS event such as highway condition or traffic movement.
HIGHWAY HAZARD—is any object, structure, or part of the highway environment which has collision potential. It is judged in terms of the probability for your vehicle running into it.
INTENDED PATH OF TRAVEL (or PATHWAY)—is that traffic lane or strip of roadway, visualized by the driver, as wide enough and long enough to permit the forward movement of his or her vehicle.
JUDGEMENT—is the ability to size up a situation and make estimates about its amount or importance. Good judgements can be made when proper rules and standards are used.
PREDICT—is to tell in advance what another traffic unit will probably do.
SAFE PATH OF TRAVEL (or PATHWAY)—is one free of hazards at the time of intended use.
TRAFFIC HAZARD—is any traffic unit which has closing potential with your vehicle as you follow your intended path of travel.
TWELVE-SECOND TRAVEL PATH (or PATHWAY)—is the distance that extends twelve seconds ahead of your vehicle and long the intended path of travel.
>TRAFFIC COLLISIONS HAPPEN BECAUSE TWO OR MORE PERSONS TRY TO US THE SAME SPACE AT THE SAME TIME.
>A SAFE PATH OF TRAVEL IS ONE FREE FROM HAZARDS AT THE TIMEOF INTENDED USE.
REQUIREMENTS FOR CAR CONTROL
-TRACTION
-SPACE
-TIME
REQUIREMENTS FOR DRIVER ACTION
-TIME
-VISIBILITY
A CAR IS DRIVEN ALONG AN INTENDED PATH OF TRAVEL WHICH IS MADE UP OF THREE PARTS.
TWELVE-SECOND TRAVEL PATH
FOUR-SECOND STOPPING ZONE
TWO-SECOND FOLLOWING DISTANCE
THE PURPOSE OF EVLUATION
-IS MY PATH CLEAR OR NOT CLEAR??
HTS HAZARDS AND CONDITIONS THAT AFFECT A DRIVER’S PATH OF TRAVEL:
ongoing cars
oncoming cars
weather
reduced traction
visibility
space
obstacles
passing cars
signals
sign
intersecting cars
entering cars
animals pedestrians
merging cars
GENERAL GUIDES
EVALUATE
JUDGE
PREDICT
>EVALUATE HAZARDS IN ADVANCE OF FOUR-SECOND ZONE
>JUDGE HAZARDS FOR CLOSING PROBABILITIES
>EVALUATE EVIDENCE FOR AND AGAINST CLOSING
>PREDICT HIGH AND LOW CLOSING PROBABILITIES
>PREDICT WHERE AND WHEN CLOSING WILL HAPPEN
HOW TO EVALUATE HIGHWAYS FOR AREA OF REDUCED TRACTION
-HOW MUCH?
-EFFECT ON CAR CONTROL?
-CHANCE FOR HITTING HAZARD?
HOW TO EVALUATE HIGHWAY FOR AREAS OF REDUCED VISIBILITY
-COMPARE SIGHT DISTANCE WITH STOPPING DISTANCES
-COMPARE STOPPING DISTANCES WITH VIEW ALONG SIDE ROADS
HOW TO EVALUATE HIGHWAYS FOR AREAS OF REDUCED SPACE
-IS THERE REDUCE TRACTION OF VISIBILITY TOO?
-WILL CHANGES IN DIRECTION BE REQUIRED?
HOW TO EVALUATE TRAFFIC HAZARDS
-FOR ONCOMING CARS SITUATIONS
-FOR FOLLOWING CAR SITUATIONS
-FOR ONGOING OR CARS AHEAD
-FOR ENTERING AND MERGING CARS
-FOR INTERSECTING CARS AND PEDESTRIANS
-WHAT MOVE WILL CAUSE THE CLOSING??
KNOW PROBABLE ERRORS
-SEEING ERRORS
-FAILS TO YIELD
-FAILS TO ADJUST SPEED
-IMPROPER CAR CONTROL
-FAILS TO SIGNAL
-SWERVES OR STOPS SUDDENLY TO AVOID OTHER USERS
EVALUATE EVIDENCE FOR AND AGAINST CLOSING
-JUDGE EFFECTS ON TRAFFIC CONTROLS
-JUDGE EFFECTS OF HIGHWAY CONDITIONS
-JUDGE THE PROBABILITIES FOR ERRORS
-PREDICT HIGH OF LOW CLOSING PROBABILITY
PREDICT WHERE AND WHEN
-HOW MUCH OF THE PATHWAY WILL BE USED??
-WILL THE HAZARD BE IN TWELV-SECOND PATHWAY??
CASE STUDY DIAGRAMS
SYMBOLS FOR CAR ACTIONS
Turn Signal Lights
Vehicle Direction
-full turn
-quarter turn
-straight ahead
-blank for parked
Speed of Car
-00 when parked
Car Designation
Stop Lights
Signal Lights
Flasher Lights
Back-up Lights
Direction for Backing
LEFT LANE HAZARDS
WHAT TO LOOK FOR
an oncoming car that is moving over toward the center line, signaling or slowing down.
an oncoming car could make a left turn into your path.
situations in the oncoming lanes that could cause the oncoming driver to swerve over the center line.
an oncoming car could swerve or be crowded over the center line as a result of an action of an action of a car alongside.
watch the problems of the driver ahead. this also included the lanes to the right and left.
the car ahead of you could stop suddenly. this can happen in any lane of any kind of street.
watch the problems that develop ahead of drivers in the right lane.
the care in the right lane beside you could swerve to miss one of the many right lane problems.
RIGHT LANE HAZARDS
WHAT TO LOOK FOR
the car ahead of you turning right could stop for people walking in the crosswalk.
you are one lane width closer to the car that might run a light or stop sign.
a parked car might want to go straight when you want to go right.
a person sitting in a car could pop a door out into your lane.
brake lights could mean that the parked driver is ready to pull out.
back up lights and an open parking space mean that the car ahead might parallel park.
a car could stop to pick up a peron or let someone off.
a person could step from between parked cars.
a car should swing out of a parking space into your lane.
exhaust fumes should alert you.
wheels pointed out also swerve as a warning.
A car in the left lane beside you could swerve into your path.
this person is unlocking the door. it could swing into your lane.
the back of this car is out in the street. be careful about swerving left.
a person sitting in a car should alert you for possible action.
back up lights and wheels pointed right mean the front could swing out into street.
BRIDGE-WIND FROM LEFT
Car swerves right.
Cross wind again.
No wind here.
Car swerve left.
GROVE TREES-WIND FROM RIGHT
Car swerve left.
Cross wind here.
No wind here.
Car swerves right.
MEET LARGE TRUCK-WIND FROM LEFT WIND FROM RIGHT
Car swerves right.
Cross wind here.
No wind here.
Car swerves left.
PASS LARGE TRUCK
Car pushed left.
Strong wind blast.
No wind here.
Car swerves right.
CASE #1 THE SUPERMARKET SHOPPER
YOU ARE DRIVING CAR “E” IN A BUSINESS DISTRICT. YOU CAN SEE THAT CAR “B” WILL NOT BE ABLE TO COMPLETE THE TURN. CAR “A” AND “C” CANNOT SEE CAR “F.” CAR “A” IS ABOUT TWO SECONDS BEHIND CAR “B.”
CASE #2
THE UNDERPASS SCISSORS MANEUVER
RAMP GOING TO
UPPER LEVEL
ROADWAY ABOVE
RAMP COMING FROM UPPER LEVEL
YOU ARE DRIVING CAR “B” AT AN INTERCHANGE
CASE #3 THE PASS WITH HAZARD ON RIGHT
MAIL BOX
YOU ARE DRIVING CAR “A.” YOU HAVE NARROW SHOULDERS AND LIMITED VISIBILITY TO YOUR LEFT. YOU STILL HAVEN’T MADE EYE CONTACT WITH DRIVER OF PANEL TRUCK “C.”
CASE #4 THE LEFT TURN AGAINST TRAFFIC
YOU ARE DRIVING CAR “B.” YOUR SIGNAL LIGHTS ARE GREEN.
CASE #5 THE NARROW DRIVEWAY
YOU ARE DRIVING CAR “A” IN A
RESIDENTIAL DISTRICT. THE
CURBS ARE SHARP AND THE
DRIVEWAY IS SLIGHTLY UPHILL.
THERE IS NO DRIVER IN CAR “B.”
CASE #6 THE PARALLEL PARKERS
YOU ARE DRIVING CAR “A”
IN A BUSINESS DISTRICT.
CAR “C” HAS JUST HIT
THE CURB. THE DRIVERS
OF BOTH CAR “C” AND
CAR “G” ARE LOOKING
FORWARD. CAR “B” IS
BEGINNING TO CROWD
THE LANE LINE. THE
OTHER PARKED CARS DO
NOT HAVE PERSONS IN
THEM.
CASE #7 THE FOLLOW PASS
CAR “C” HAS JUST CHANGED LANES TO
PASS CAR “B.”
YOU ARE DRIVING CAR “A” IN A RESIDENTIAL DISTRICT
CASE #8 THE FRINGE BUSINESS DISTRICT
NO DRIVERS IN
PARKED CARS.
STREET CHANGES FROM
FOUR LANES TO TWO LANES DUE TO PARKED
CARS.
BUILDING MAKE FOR
POOR VISIBILITY.
YOU ARE DRIVING CAR “A” AND LEAVING THE DOWNTOWN
BUSINESS DISTRICT.
CASE # 9 RIGHT TURN WITH PARKED CARS
YOU ARE DRIVING CAR
“B” IN A BUSINESS
DISTRICT.
THERE ARE DRIVERS IN
BOTH CAR “C” AND CAR
“E.” THERE ARE NO
DRIVERS IN OTHER
PARKED CARS.
CAR “A” IS CLOSER THAN
TWO SECONDS.
CASE #10 THE BUSY RAMP
YOU ARE DRIVING CAR “B” ON A RAMP AT
ONE INTERCHANGE. YOU ARE ABOUT ONE
SECOND AWAY FROM CAR “C” AND CAR “A.” CAR “F” IS TAILGATING CAR “D” ON THE FREEWAY. THE ACCELERATION LANE IS UP TO STANDARDS. CAR “C” IS BEGINNING TO ACCELERATE.
CASE #11
THE GRAVEL SIDE ROAD
YOU ARE DRIVING CAR “A” IN A RURAL
DISTRICT. THERE IS GRAVEL ON THE
PAVEMENT AT THE INTERSECTION. BOTH
SHOULDERS ARE NARROW AND NOT LEVEL
WITH THE ROADWAY. CAR “B” HAS JUST
BEGUN RAPID ACCELERATION. CAR “C” IS
ABOUT TWO SECONDS FROM THE SIDE ROAD.
CASE #12 THE NARROW SIDE
STREET
YOU ARE DRIVING CAR “A” IN
A RESIDENTIAL DISTRICT.
CAR “C” IS ABOUT TWO FEET
FROM CURB. CAR “D” IS LESS
THAN TWO SECONDS FROM CAR
“C.” THERE IS NO ONE IN
CAR “E.” YOU HAVE MADE EYE
CONTACT WITH THE DRIVER OF
CAR “B.”
CASE #13 THE ANGLE PAKER
YOU ARE DRIVING CAR “A” IN THE BUSINESS
DISTRICT. CAR “E” HAS JUST STOPPED.
CAR “G” AND CAR “H” ARE FOLLOWING
LESS THAN TWO SECONDS. CAR “I” IS
DRIVING IN THE BLIND SPOT OF CAR “H.”
THERE ARE NO DRIVERS IN THE PARKED CARS.
ANSWER SHEET FOR EVALUATION OF CASE SUTDIES
NAME SCORE
INSTRUCTIONS: Each case (traffic situation) diagram should provide you with enough evidence to make judgments and predictions. The drawings are made to scale when practical. Remember that at 10 mph a car will travel one car length in one second. Use 15 feet as an average car length if you need to figure distances.
Study each case carefully and apply your stored information related to laws, vehicle capabilities, roadway conditions and driver actions. Then write your answers. Write none for those effects that do not apply. Please do not write on the diagram sheets.
CASE # and TITLE
1. What is the likely effect of TRAFFIC CONTROLS on other users?
2. What is the likely effect of HIGHWAY CONDITIONS on other users?
a. SPACE
b. VISIBILITY
c. TRACTION
3. What are the likely ERRORS for any of the other users?
4. Which car (letter) do you predict has a high closing probability on your intended path
of travel? .
5. About when do you predict the closing to take place? (circle one)
a. Within 2 second part of path. c. Within 4-12 second part of path.
b. Within 2-4 second part of path. d. Outside 12 second part of path.
6. About how much of your pathway or lane will be used? (circle one)
a. Less than one-half.
b. One-half.
c. All or more.
CHECKLIST FOR CLOSING EVALUATIONS
Observer or Driver Instructions—In advance of each block or segment of roadway, you will orally indicate whether the path is “CLEAR” or “NOT CLEAR.” For each NOT CLEAR situation, you will tell when and where the hazards with high closing will probably close. You will have a choice of three closing locations that make up part of the intended pathway—(1) between four and twelve seconds, and (2) over twelve seconds.
Recorder Instructions—Check in the proper column the closing locations picked for all NOT CLEAT situations. Then after a discussion with the teacher and other students, score correct or incorrect. Use “C” for correct.
T S N T S N
R CLOSING C A R CLOSING C A
I LOCATION O M I LOCATION O M
A Over R E A Over R E
L 2-4 4-12 12 E L 2-4 4-12 12 E
1 1
2 2
3 3
4 4
1 1
2 2
3 3
4 4
1 1
2 2
3 3
4 4
GUIDE FOR UNIT 7 SLIDE PROGRAM
The slides used in Unit 8 may be used for practicing evaluations. The following slides and suggested are provided as an example of one approach.
SLIDE # QUESTIONS FOR STUDENT RESPONSE
ID-1-B What highway hazards are there?
What traffic hazards are there?
Is there a probable closing with the truck? Trees?
ID-1-3 What are the traffic hazards?
Predict what course of action the blue car will take.
What is the closing probability?
ID-1-5 How would you evaluate space? Visibility?
What predictions can be made about traffic hazards?
ID-2-4 Is there a probable closing with the pedestrian?
Why? Where? How much?
ID-2-5 Describe space ahead and to the sides.
What are the highway hazards?
What are closing probabilities with traffic hazards?
ID-2-6 Describe the closing probability with oncoming car.
What other traffic hazards are there?
What are their closing probabilities?
ID-3-4 What is the closing probability here?
Is your pathway clear or not clear?
ID-3-8 What predictions can be made here?
What are the closing probabilities?
ID-4-1 What are the highway hazards?
What are the traffic hazards?
Explain the closing probabilities.
ID-4-5 What predictions car you make here?
Where would the closing most likely take place?
ID-4-7 What traffic hazards are there?
Where would the closing most likely take place?
ID-4-8 How much will your traction be reduced?
What are the highway and traffic hazards?
What are the closing probabilities for each?
Source: https://t-tees.com
Category: WHEN
