unit 27
Every collision is different, but the specific way a collision occurs has a drastic effect on its consequences. Generally, for example, head-on collisions differ from side-impact collisions in very important ways. It's important that you understand the basic effects of each type of collision so that you can assess a potential or immediate crash risk and respond appropriately.
A head-on collision occurs when a vehicle strikes another object directly in front of it. In this case, 100% of the vehicle's speed is directed towards the point of impact. Almost every collision is a head-on collision for one of the vehicles involved. In a head-on collision, occupants are thrown towards the front of the vehicle. As always, seat belts and air bags are extremely important safety measures. The front crumple zone also offers vital protection: it buckles on impact, increasing the duration over which stopping force is applied to the vehicle. This reduces the impulse felt by occupants, ultimately reducing injury.
A rear-end collision occurs when a vehicle is struck by another object from behind. In this case 100% of the vehicle's speed is directed away from the point of impact—the faster the impacted car is traveling, the less forceful will be the impact. In a rear-end collision, occupants are thrown towards the back of the vehicle. Whiplash, caused by the neck snapping forward and backwards, is a common injury in these collisions. The rear crumple zone offers important protection, but some vehicles, like many minivans, have no rear crumple zone.
A rear-end collision can push your vehicle forward. This is especially dangerous when you're waiting at a traffic light, STOP sign, or YIELD sign—you may be pushed into cross traffic. To avoid being rear-ended, check your mirrors often. Keep track of the vehicles behind you. Try to maintain a safe distance between the vehicle directly behind you, and brake early to give the driver advance warning when you slow down or stop. Signal before every lane change to avoid being struck from behind by a vehicle in the next lane. To avoid rear-ending another vehicle, maintain a safe following distance behind it. Look farther than just the vehicle in front of you, so that you can have advance warning before it slows down or stops.
You will face severe penalties if you are guilty of a hit-and-run. If you leave the scene of a collision which you were involved in without stopping to render aid and exchange information, you may face penalties including a license suspension and: A jail term of up to 20 years and a fine of up to $10,000 if someone was killed or seriously injured A jail term of up to five years and a fine of up to $5,000 if anyone received an injury A jail term of up to 180 days and a fine up to $2,000 if there was $200 or more worth of property damage A $500 fine if there was less than $200 worth of property damage
As you review the information presented in this unit, consider how to incorporate the following topics into your driving plan. To reduce risk on the road, you must: Effectively manage centripetal and centrifugal forces so you can stay in your lane as you drive through a curve Understand the consequences of different types of collisions and develop effective strategies for responding to each of them Handle your vehicle carefully in an emergency so you can avoid catastrophic losses to traction or balance Determine and choose the safest way to enter a collision when it's impossible to avoid one completely Act promptly and responsibly to prevent further injury following a collision
On the Road Ahead Crash Physics Movie: Understanding Car Crashes Collision Types Avoiding and Reducing Impact Post-Crash Safety and Responsibility Reducing Risk: Driving Plan/Unit Review
Before discussing collision types and collision avoidance, it will be helpful for you to recall the physics of car crashes. You don't need to calculate anything, but if you have an intuitive understanding of the basic relationships in play during a collision, it will be easier for you to make decisions that positively affect the outcome.
Give accurate facts to the police when they arrive. When speaking to the police following a collision, you should never attribute fault to the other driver or yourself. Do not leave the scene until all relevant information has been shared with all parties involved. Seek medical attention promptly. You may have been injured in a way that is not immediately apparent. Contact a mechanic about any necessary repairs. For insurance purposes, you are generally required to get two estimates concerning the cost of repairs. Mechanics must report any vehicle that arrives at their shop showing evidence of a collision. Notify your insurance agent as soon as possible. Your insurance company may refuse to pay your claim if you do not contact them within the time specified in your policy.
Call the police immediately after a collision if one of the drivers involved is intoxicated, has no insurance, or leaves the scene of the crash. Uninsured motorist insurance policies will pay for your damages only if the crash is reported to the police. You must report any collision that you're involved in to your insurance company, no matter how much damage it caused. You may be fined $350 and your license may be suspended if you are found to have been driving without properly meeting your financial responsibility requirement.
When performing emergency maneuvers, your vehicle's traction and balance may be pushed to their limits. Remember that hard or sudden braking, as well as sharp steering, may lead to a loss of traction, causing you to lose control of your car. You must often brake to avoid a hazard, but steering is important, too. If you cause your vehicle to skid, there may be no way to avoid running straight into a hazard you could have avoided by steering. If your braking and road conditions cause you to enter a skid, remember how to respond: take your foot off the accelerator and the brake pedal, look and steer where you want the car to go, and make minor adjustments to prevent oversteering after recovering.
Finally, remember that excessive braking and steering can cause your vehicle to lose balance. If you brake hard and steer sharply to one side, your vehicle may roll over towards the opposite side. Such a complete loss of control can have devastating consequences. You must keep all four wheels on the ground and maintain good traction with the road in order to successfully handle your vehicle in an emergency.
If anyone is injured or killed, you must call the police immediately. You and any other drivers involved in a collision must share certain information with the police and each other, including: Your names Your addresses Your drivers license numbers Your license plate numbers The names and addresses of your insurance companies—if you only get the company name, you can get the rest of the information by calling 1-800-252-3439 You should also note the names and addresses of any passengers involved in the collision, as well as where they were sitting and the extent of their injuries.
If you hit a parked vehicle or another form of property, try to find the owner. If you cannot find the owner, leave a note with your name, address, and phone number under the windshield, as well as a description of the circumstances of the collision. Report the collision without delay to the police. You should follow this same procedure if your car rolls away and hits another vehicle after you have parked it.
Check traffic and signal. If you don't think you will have enough room in time, use your horn to let other drivers know that you're coming. Sharply steer left while gripping the steering wheel firmly. The moment your right front wheel touches the edge of the road, counter-steer right. Your success (and survival) in such a critical situation depends on you remaining in control of the steering.
If you realize that a collision with another vehicle or a stationary object is imminent, you can minimize the force of impact in the following ways: Slow down as much as possible before impact Strike the softest object you can Strike a vehicle moving with the lowest speed relative to you—preferably a vehicle moving away from you Strike an object at a wide angle rather than head-on Strike a broad object instead of a narrow one Strike a loose object rather than a fixed one
When you enter a turn or a curve, your car's inertia tries to keep it moving in a straight line, while the angle of your wheels causes friction that tries to move it towards the curve. These are called centrifugal and centripetal forces. When you enter a curve, you balance centripetal force (driving into the curve) against centrifugal force (being pulled out of the curve). An imbalance in these forces will cause you to leave your lane.
If you steer too sharply for your momentum, excessive centripetal force will pull you too far into the curve. In the inside lane of a curve, this will pull you off the road. In the outside lane, this will pull you across the centerline and into oncoming traffic. What's more common is an excess of centrifugal force. If you drive too fast considering your weight and angle of steering, excessive centrifugal force will pull you into a straighter line, failing to turn enough. In the inside lane of a curve, this will pull you across the centerline and into oncoming traffic. In the outside lane of a curve, this will pull you off the road.
A side-impact collision occurs when a vehicle is struck primarily on the side of the passenger compartment—on or near a side door. These collisions are particularly dangerous because crumple zones don't exist in these locations, and because the impact often occurs much closer to where the occupants are seated.
In a side-impact collision, the force of impact is transferred immediately and directly to the passenger compartment. Doors and windows will crush and be pushed towards the occupants as the occupants are thrown towards the point of impact. These collisions occur most often in intersections and parking lots, and are usually caused by a blatant disregard for right-of-way. Always obey the rules of right-of-way.
You must turn in a report whether or not you are responsible for the collision. If a driver is incapacitated in a collision, this report should be filed by a passenger if there is one capable of doing so. These reports are confidential, but available to all parties involved. They are only meant to indicate involvement in a collision and cannot be used in civil cases. At the scene of the collision and when filing this report, you should not admit or attribute fault. Fault will be determined in court or by the insurance companies of the drivers involved.
In order to be prepared for any potential legal issues in the future, following a collision you should always get the names and addresses of everyone present at the collision scene, including all drivers and witnesses. If possible, make a sketch or take a photo of the collision scene. You should record as many facts related to the collision as possible, such as the time, date, location, weather, and driving conditions, as well as the name of the hospital where the injured are taken and the badge number of the police officer at the scene.
To recover safely when your car's right wheels have rolled off the road, you need to perform the following tasks: Hold your steering wheel firmly and continue to move straight ahead towards a safe target area. Relax pressure on the accelerator and slow down until you are moving about 5-10 mph. Avoid braking abruptly. Position your vehicle so that it straddles the edge of the roadway. Look for an appropriate place to get back on the roadway. You should find an area where the pavement and the shoulder are at about the same level. Check for traffic on the road and in your blind spot and activate your left turn signal.
It is dangerous to let panic control your actions. For instance, you may immediately steer sharply left to get back to the road as soon as you drive off it. As a result, your vehicle will be thrust into the roadway, cross the center line, and roll over on the other side of the road. Many fatal one-car crashes have been caused by panic-steering instead of allowing the car to slow down.
When you are involved in a collision, the first thing you must always do is stop immediately. Failure to stop is a serious offense. You may be charged with a hit-and-run. Immediately following a collision, move your vehicle to the side of the road away from the flow of traffic unless it is so damaged that it is impossible to move. Turn off the engine. Once you have safely stopped the vehicle, exit your car cautiously to identify yourself to all parties involved and aid anyone injured in the collision.
Many collisions happen in places where it is dangerous to stop, such as ramps, shoulders, medians, or intersections. If the collision occurs in a place where it is likely to significantly interfere with traffic, you can move to a designated investigation site nearby as long as all vehicles can be moved safely. The site must be agreed upon by all drivers involved in the collision.
The two most prevalent types of error are recognition errors (including distraction, inattention, and failure to scan adequately) and decision errors (such as speeding, maneuvering illegally, or failing to correctly predict the actions of another driver).
Many of these driver errors are heavily influenced by certain factors: Intoxication and fatigue cause inattention, poor vision, bad judgment, lack of coordination, and possible loss of consciousness Distraction causes inattention, rushed decisions, and hesitant actions Speed gives you less time to see objects on the road, less information before making a decision, and less control when executing a maneuver Aggression causes distraction, bad judgment, and poor coordination Intoxication, fatigue, distraction, speed, and aggression are some of the most influential factors leading to fatal collisions.
The way you're sitting inside your vehicle also affects how much injury you suffer. Sit up straight at all times, with your head resting against the headrest. Keep all body parts at least ten inches from where any air bag will deploy. Take your foot off the brake pedal just before the moment of impact: tremendous forces on your vehicle's wheels can be transmitted up through the brake pedal, breaking your leg. Brace yourself against your seat and the steering wheel, if possible. Tighten your muscles to help guard against organ damage.
No one expects to get into a collision when they get on the road, yet hundreds of collisions happen every day. The chances are good that eventually you'll be involved in a collision, too. If you're involved in a collision, don't panic. While shock and anxiety are natural responses, you must remain calm until the immediate situation has been resolved. You could make the situation worse if you are unable to think clearly. Moreover, you may be less prepared to complete the tasks you are legally required to perform in a collision.
Fortunately, it's not difficult to prevent a lot of these errors before they have a chance to occur. By consciously making better choices and practicing safe behavior behind the wheel, you can keep yourself in the best position to avoid collisions on the road. Remember never to drive if you're even slightly impaired due to alcohol, drugs, or fatigue. Impairment quickly destroys your ability to determine how impaired you are, then makes you prone to recognition, decision, performance, and non-performance errors.
Pay attention to the road at all times. You must avoid many different sources of distraction, including music, passengers, food, and collisions on the roadway. Noticing hazards at the last second won't help you avoid them—you must actively search the driving environment for potential and imminent conditions. Never speed or drive aggressively. Always drive at a speed appropriate for current driving conditions, never more than the posted speed limit. Be courteous to other drivers and obey the law at all times. Maintaining a safe following distance is extremely important to your ability to recognize, understand, and safely react to changing road conditions.
Other important types of collisions and emergencies include rollovers, which often occur when vehicles leave the road. Rollovers produce forces that very easily eject unbuckled occupants. They are one of the deadliest types of collisions. SUVs and other vehicles with a high center of gravity are more susceptible to rollovers.
Single-vehicle collisions occur when a single vehicle strikes an immobile object, usually off the road. Maintain control of your vehicle and, above all, stay in your lane. Unless debris or another hazard blocks your path, you will not suffer a single-vehicle collision if you stay in your lane. Unfit drivers are often at fault in their own single-vehicle collisions. Consider the typical collision suffered by drowsy drivers: a single vehicle leaves the road and collides with a stationary object at a high speed, while the driver makes no attempt to avoid the object. These collisions are extremely deadly and are easily avoided by those fit to drive.
If you kill or injure an animal, pull over to the side of the road and stop. Try to find the owner. If you cannot find the owner, call the Humane Society or the police. Do not try to move an injured animal, but never leave an injured animal to die—it is inhumane and cruel.
When you are involved in a collision that results in injury, death, or property damage of at least $1,000, you must report the collision to the DPS within ten days of the event. If an officer visits the scene of the collision, he or she will file a report with the DPS that fulfills this requirement. If you don't file a report within 10 days of the collision, you may be fined up to $500.
Occasionally the right wheels of your car will drive off of the paved roadway inadvertently as the result of a temporary loss of control or the need to avoid an immediate hazard. While the shoulder will sometimes even and in good condition, in many situations, the shoulder will be lower than the roadway and unpaved. Upon rolling off the roadway, the front wheel of your car may suddenly drop down, which can disrupt the distribution of weight and balance in your vehicle. Moreover, the unstable surfaces of the unpaved area make traction unreliable. Generally, you will have to respond immediately to avoid more significant risks. However, attempting to re-enter the roadway by braking hard or turning sharply can cause your vehicle to move across the road into oncoming traffic and roll over.
When your vehicle's right wheels drop off the pavement, the most important thing to remember is: do not panic. Using the off-road recovery technique described in the following slides, you can and will recover from this situation.
The presence of a collision in the roadway or on the side of the road can increase the chances that another driver may become distracted or need to react suddenly, causing another collision. In order to prevent further damage, turn on your hazard lights if possible and set up flares or reflectors at least 100 ft in front of and behind your car (or 500 ft in high-speed traffic). If these devices are unavailable, you can try to warn traffic by standing ahead of the site and directing vehicles around your car. Never position yourself in a way that would endanger yourself or others. If there has been a gas spill, avoid the use of flares as well as other potentially dangerous activities like smoking.
You are legally required to determine who was involved in the crash and whether anyone involved has been harmed, and provide assistance to anyone who's been injured. However, you should provide medical aid only if you know what you're doing. Improper medical care will often make the situation much worse. In most cases, assistance will consist of calling for an ambulance or paramedics. Be sure that you identify the place of the collision clearly and precisely when you call 911. If the injury is not severe, you may offer to transport the injured party to medical care yourself.
When your car expends or absorbs energy to speed up or slow down, you may feel a pull or a jolt, called impulse. Impulse increases as the energy or force increases, and increases as the duration of the force decreases. You'll feel a harder jolt if you speed up or slow down suddenly. Consider: coming to a stop from 60 mph in ten seconds doesn't hurt you or your vehicle because the force of this event is spread out over a long time. But if you hit a wall and come to a stop in just half a second, you'll feel twenty times the impulse, causing severe damage.
A large impulse can be very deadly, which is why braking, air bags, and crumple zones on your vehicle all increase crash safety. When you brake, or impact an air bag, or come to a stop more slowly as the front or rear of your vehicle collapses, the impulse of your collision is reduced. For this reason, side-impact crashes are often more deadly to occupants than head-on or rear-end collisions. Front and rear crumple zones slow down the impact, but a strike against a vehicle's door or B-pillar transmits the force of impact over much less time. Keep this in mind when a possible collision is imminent.
If it is safe and you are competent to do so, you should attempt to provide medical aid to anyone who is seriously injured. Even basic medical care provided in the first few minutes after an injury can mean the difference between life and death. Help anyone who is not already walking and talking. Firmly apply thick cloth pads or bandages to bleeding wounds. These pads should be as clean as possible. Begin artificial respiration at once on anyone who appears not to be breathing, if you are certified to do so. If you have completed a certified first-aid course, you may also attempt to treat severe bleeding or shock. Do not move an injured person unless they are in a burning vehicle or in other imminent danger—it may make their injuries much worse.
According to the Good Samaritan law: A person who in good faith administers emergency care is not liable in civil damages for an act performed during the emergency unless the act is willfully or wantonly negligent. You should provide any emergency care you are capable of providing. You will not be held responsible for any damages that accidentally result from your care unless you expect payment, are aware that injury will result from your treatment, or are found responsible for the collision.
Finally, pay attention to other drivers. Never make any assumptions concerning another driver's intentions, sobriety, alertness, or respect for the law. Treat every road situation as new and unpredictable. Everyone makes mistakes from time to time. Over time you'll encounter a great number of drivers on the road, so expect them to make mistakes, and have an escape plan for when they do. Make a habit of thinking ahead and you'll find there's a lot you can do to prepare for possible and imminent changes in the driving environment.
Awareness of the driving environment is extremely important when dealing with an emergency. Seeing hazards will help you avoid them, but seeing hazardous situations and understanding them will help far more. Scan the road and consider the most likely consequences of the conditions you observe. Prepare responses to possible situations: make room for motorcyclists passing you from behind; brake gently if a vehicle far ahead of you brakes suddenly; look for space in an adjacent lane if a vehicle ahead is broken down in your lane.
If your vehicle falls into deep water and begins sinking, leave it behind and concentrate on your safety and the safety of the other occupants. If your car enters water deep enough to sink in, immediately roll down all windows. This will help it fill with water, which is actually a good thing. If your vehicle becomes submerged with its windows rolled up, the pressure of the water on your doors may be too great to allow you to open them. If you open your windows late, the rush of water may make breathing and escaping more difficult. Unbuckle yourself, breathe in as much air as you can hold, and exit the vehicle.
Recall the primary causes of collisions: the actions of the driver, the condition of the roadway, and the condition of the vehicle being driven. Driver error plays a part in 94% of all collisions, and consists of poor recognition, poor decisions, poor performance, and "non-performance errors" such as falling asleep.
When it is safe, start your off-road recovery by steering sharply left. The more severe the drop-off, the more you will have to slow down and turn sharply to get back on the pavement. As soon as your right front tire comes back onto the pavement, counter-steer sharply right to straighten your vehicle. Finally, position your car in the center of the lane, cancel your turn signal, and adjust your speed to the traffic flow. If traffic is heavy when you drive off the roadway, you should leave the roadway entirely and wait for a large gap in traffic before you start to reenter.
Sometimes the situation is more complicated. For instance, after your car's right wheels have driven off the road, you may realize that there is an obstruction like a pole, traffic sign, or guardrail ahead of you on the shoulder. These circumstances require you to make your off-road recovery quickly. In the limited time available to you, you won't be able to slow down or look for an ideal spot to re-enter the roadway.
When responding to an emergency situation, change the way you handle your vehicle only just as much as is needed to safely avoid hazards. If you jerk your steering wheel to one side or slam on the brakes when it's not necessary, you may make the consequences much worse. When avoiding a head-on collision, always evade to the right unless you're sure that evading to the left is the only way to avoid the collision. If the other driver corrects his or her mistake, the vehicle will move to your left—so you don't want to move there. Further, if you successfully evade the other vehicle, you should try to end your maneuver in your own lanes of traffic rather than in opposing lanes.
You may be able to avoid a rear-end or side-impact collision by speeding up and steering out of the way. In a rear-end collision, increase your speed to reduce the force of impact and make the damage less severe. In a side-impact collision, speed up or slow down to change the point of impact to your engine compartment or rear end, which will reduce damage to the passenger compartment. As long as it doesn't point you towards another danger like a cliff or oncoming traffic, steer away from the oncoming vehicle. This will reduce the force of impact and make the point of impact closer to the rear end.
Both you and your car have momentum, and a tendency to maintain it, called inertia. When the car strikes an object, your body will keep moving until something stops it. If you're wearing your seat belt, it holds on to your body, stopping you at the same rate as the car. But if you're not wearing your seat belt, something else will have to stop your body. This means crashing into the dashboard, the windshield, maybe even the pavement after exiting the windshield—and any of these impacts can be deadly.
Your car's kinetic energy increases as weight increases, and increases with the square of speed. If you slam on the brakes or crash into a wall, your car must absorb energy equal to its kinetic energy before coming to a stop. Importantly, this means that stopping distance and force of impact increase with the square of speed. Driving at an appropriate speed, and slowing down as soon as you see hazards ahead, are some of the most effective actions you can take to increase maneuverability and reduce crash severity. Remember: stopping distance at 50 mph is four times that at 25 mph, and a crash at 75 mph has nine times the force of impact of a crash at 25 mph.
