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Proving negligence in rear-end collision cases.

Of all the types of automobile accidents, rear-end collisions are the most common. This is true because most people drive too fast for the existing conditions and follow the car ahead of them too closely. Also, many drivers fail to keep a proper lookout for possible dangers ahead.

Even though these collisions are common, most jurors do not truly understand why they occur. Few understand the danger caused by following too closely and most jurors do not normally drive any differently than the rear-ending driver under the facts presented. Therefore, they, have a tendency to be sympathetic to that driver.

This means that a lawyer trying a rear-end collision case must do more than just prove that the plaintiff's vehicle was rear-ended. The lawyer must demonstrate to the jury how the collision occurred and what the rear-ending driver did wrong in order to obtain a finding of negligence. In most cases, expert testimony based on a relatively inexpensive analysis of the facts can be presented to explain why the rear-ending driver was at fault.

The law pertaining to these collisions is relatively clear and uniform throughout the country: A motorist has a duty to "exercise reasonable care to avoid a collision with the vehicle ahead."(1) The driver of a following vehicle must be able to stop or take other appropriate measures to prevent running into the preceding vehicle should it suddenly slow or stop. The driver of a following vehicle must stay back a reasonably safe distance to provide for this contingency and must travel at a speed consistent with an ability to stop within the distance between the two vehicles. The motorist must also maintain a proper lookout for the vehicle ahead in order to take appropriate measures to avoid a collision.(2)

Most states impose, by statute, a duty on drivers of following vehicles, requiring them to keep an "assured clear distance" between the following vehicle and the preceding one so that the following vehicle can be safely brought to a stop without colliding with the preceding vehicle or veering into other vehicles, objects, or people on or near the street or highway.(3) But there are no hard-and-fast rules as to how close a motorist, in the exercise of ordinary care, should follow another vehicle. The only rule governing the interval to be maintained between vehicles is that of reasonable care under the circumstances.(4)

The collision itself is some evidence of negligence on the part of a driver who strikes a car from the rear.(5) However, "the mere occurrence of a rear-end automobile accident is not evidence of negligence as a matter of law.(6)

A question of fact as to negligence is usually presented when a motor vehicle strikes one in front of it going in the same direction.(7) The plaintiff must prove specific acts of negligence by the following driver and must also prove proximate cause.(8)

Even though the mere occurrence of a rear-end collision is not evidence of negligence as a matter of law, the rear-ending driver was almost always negligent. This is so because that driver is required to maintain an assured clear distance between his or her vehicle and the one ahead. In most cases, the rear-ending motorist was either following too closely for the speed the vehicles were traveling, failed to keep a proper lookout, or failed to timely apply the brakes.


To prove negligence on the part of a rear-ending driver, at the time the lawsuit is filed the plaintiff's lawyer should begin by submitting requests for admissions like the following:

* On (date), the vehicle you were driving hit in the rear a car the plaintiff was driving.

* At the time of the wreck, there were no obstructions to your vision.

* You were traveling at a speed that would not allow you to bring your vehicle to a stop without hitting the plaintiff's car in the rear.

* You did not see the plaintiff's car in enough time to take sufficient action to avoid hitting it.

* There was not enough distance between your vehicle and the plaintiff's car to allow you to avoid hitting it.

* You did not apply your brakes before hitting the plaintiff's car.

* You did not apply your brakes in enough time to avoid hitting the plaintiff's car.

The last five requests encompass negligent acts on the part of a following driver that can cause a rear-end collision. In almost every case, one or more of these requests must be admitted by the defendant. If all are denied, the defendant will have difficulty explaining why the wreck happened.

For example, if the defendant denies traveling at a rate of speed that would not allow bringing the vehicle to a stop without hitting the plaintiff's car in the rear, the obvious question becomes why did he or she not stop. If the defendant denies seeing the plainfiff's car in enough time to take action to avoid a collision, why was a collision not avoided?


After the requests for admissions have been admitted or denied, the defendant's deposition should be taken. The defendant's deposition questions should be similar to the requests for admissions. Even when the requests for admissions have been formally denied, the defendant will often admit at deposition that one or more of them are true.

The defendant should be asked

* to elaborate on the facts surrounding each of the requests for admissions,

* to give die speed he or she was traveling immediately before the wreck, and

* to estimate the distance between his or her vehicle and the plaintiff's vehicle when he or she first perceived that a rear-end collision might occur.

These facts, along with the other facts, can then be used by an expert to explain why the defendant's negligence caused the wreck.

Stopping Distance

To demonstrate that a defendant was following too closely, the defendant's total stopping distance must be calculated. This distance is composed of three elements: the braking distance, the perception-time distance, and the reaction-time distance.

The braking distance is the minimum distance it takes to stop a vehicle traveling on a particular roadway at a specific speed. The distance is calculated by using the distance-to-stop formula:

distance to stop = [speed.sup.2]/30 x drag factor

This formula will reveal the minimum stopping distance after the brakes are applied on a vehicle equipped with passenger car tires. Whether the vehicle is equipped with antilock brakes makes no difference. Antilock brakes do not shorten the braking distance; they simply give a driver the continued ability to steer while braking.

To use the distance-to-stop formula in a rear-end collision case, one must assign a speed to the defendant's vehicle using either the speed testified to by the defendant or other testimony and evidence in the case. One need not be overly concerned about using the defendant's speed estimate in making these calculations. If defendants underestimate their speed, that will actually work against them because, as will be demonstrated later, their stopping distance will be reduced because of the lower speed.

The drag factor of the roadway involved must also be known to use this formula. The drag factor is the coefficient of friction plus or minus the grade of the roadway. The drag factor is expressed as a percentage of the weight of an object that is required to push it or pull it along a given surface.(9) The grade takes into account whether the object was going uphill or downhill. The drag factor is a mathematical expression of the ability of the road surface to stop an object sliding on it. The sticker the surface, the lower the drag factor and the greater the distance it takes to stop. The rougher the surface, the higher the drag factor and the less distance it takes to stop.(10)

Many publications give drag-factor ranges for various roadway surfaces, such as cement, asphalt, gravel, ice, and snow.(11) These ranges arc best used only to get a general idea of the drag factors that might be expected for each type of surface. These publications say, ice may have a drag factor as low as .10; new, dry concrete, drag factors as high as 1.00 or 1.20. Although these ranges may be useful for illustration purposes, the actual drag factor of a roadway where a collision occurred should be used when applying the distance-to-stop formula. The drag factor at the scene should be determined under the same conditions that existed at the time of the wreck. The drag factor cm vary greatly, even on the same roadway, depending on variable conditions like temperature and humidity.

An accident reconstruction expert can determine the drag factor of a roadway at any location. The actual drag factor can then be used in making the distance-to-stop calculations.

Once the defendant's speed has been determined and the drag factor obtained, the minimum braking distance can be calculated. For example, assume a defendant testified that he was traveling 55 mph down a freeway when the vehicle ahead of him suddenly came to a stop. Assume also that the freeway was made of sharp Portland cement and that the weather was hot and dry. The drag factor of the roadway was determined to be .75.

By using the distance-to-stop formula, the braking distance can be calculated as follows:

distance to stop = [speed.sup.2]/30 x drag factor

= [55.sup.2]/30 x .75

= 3025/22.5 distance to stop = 134 feet

Therefore, once the defendant's brakes were applied, it would take at least 134 feet to bring the vehicle to a complete stop without a collision.

Perception and Reaction Times

Besides the braking distance, the distance traveled during the driver's perception time and reaction time must be taken into account. "Perception time is defined as the interval between first possible sighting of the obstacle and accelerator release."(12) Stated simply, it is the time it takes a driver to perceive a danger and begin to react. It is widely accepted that perception time for the average driver is at least three-quarters of a second. Studies show that many variables affect perception time; the three-quarters of a second is a minimum. Some drivers, under some conditions, may have a perception time of up to 2 seconds or more.(13)

"Reaction time," also called response time, "is defined as the interval between release of the accelerator and contact with the brake pedal.(14) It is the time it takes a driver to react by applying the brakes after perceiving a danger. The reaction time of an average driver is three-quarters of a second, and many courts will take judicial notice of that fact as a matter of law.(15)

To compute the distance traveled during the defendant's perception time and reaction time, the speed the defendant was traveling must first be converted from miles per hour to feet per second. Miles per hour can be converted to feet per second by multiplying the miles per hour by 1.47. Therefore, to determine the feet per second traveled by a car going 55 mph, one must simply multiply 55 by 1.47, which equals 80.85.

To calculate the distance traveled during perception time, one must multiply the 80.85 feet traveled during one second by .75, the three-quarters of a second minimum perception time, which equals 66.64 feet. Thus, at 55 mph the defendant's vehicle traveled 60.64 feet during the time it took the defendant to perceive the danger.

The same calculations must again be made for the defendant's reaction time. Since the average reaction time is also three-quarters of a second, the vehicle traveled another 60.64 feet during the time it took the defendant to react after the danger was perceived. The combined distance the vehicle traveled during the defendant's perception time and reaction time was just over 121 feet.

The breaking distance of 134 feet in this example must be added to the perception-time and reaction-time distance calculated to be at least 121 feet, for a total stopping distance of at least 255 feet. That is the minimum distance it would take the defendant to stop without having a collision.

Zone of Danger

In the example above, the total stopping distance of 255 feet is the defendant's zone of danger. If any object becomes stationary within a vehicle's zone of danger, the vehicle cannot stop without colliding with that object unless the driver can steer around the object by turning to the right or left.

The faster the speed, the greater the zone of danger. This can be illustrated by comparing the zone of danger distances for vehicles traveling at different speeds.

When a stopped or slowly moving car is rear-ended, the collision occurred because the rear-ending driver either failed to keep a proper lookout or failed to apply the brakes until the car ahead was within the zone of danger.

When two vehicles arc traveling at the same speed and a rear-end collision occurs because the vehicle in front has to come to a stop, following too closely can also be a factor.

When two vehicles travel at the same speed, a dynamic situation exists. If the vehicles have to stop suddenly, both win come to a stop in the same number of feet once the brakes are applied because both vehicles have the same braking distances. The vehicle in front will continue to move forward and away from the rear vehicle while it is stopping.

But the driver of the car behind must perceive the danger and react to the braking of the car ahead. While the car in front is braking, the car in the rear continues to move forward for at least 1.5 seconds, the driver's combined perception and reaction time (P/R time).

Even if the driver of the rear car applies the brakes instantly after realizing the car in front is coming to a stop, his or her car will have traveled the driver's P/R time distance during that interval. Thus, the rear driver must keep more than his or her P/R time distance between his or her car and the car ahead to maintain an assured clear distance.

If the rear car is moving closer to the car ahead than the P/R distance, the rear driver is following too closely In the 55 mph example, the rear vehicle would have to be at least 121 feet behind the car ahead to maintain an assured clear distance.

Illustrations Help Jury

An illustration like the one that accompanies this article can help a jury visualize the zone-of-danger concept and understand the peril caused by following too closely. In an appropriate case, illustrations can be shown through computer animation so a jury can better understand how a particular rear-end collision occurred.

Whether a rear-ending driver was at fault should not be left to speculation and surmise. With a little effort an minimal discovery, the negligence of a driver can easily be demonstrated to a jury. Through a simple scientific analysis of the facts, a jury can come to understand exactly what the driver did wrong and how that driver was negligent in causing a collision.

Dale Felton, a member of the Texas Association of Accident Reconstruction Specialists, practices with the law office of Felton and Associates in Houston


(1) 2 PATRICK D. KELLY, BLASHFIELD, AUTOMOBILE LAW AND PRACTICE 703, [section]113.12 (rev. 3d ed. 1979) (citation omitted); see also Renshaw v. Countess, 289 S.W.2d 621, 624 (Tex. Civ. App. 1956); Caraway v. Behrendt, 224 S.W.2d 512, 514 (Tex. Civ. App. 1949). (2) 2 KELLY, supra note 1, at [section]113.13. (3) See, e.g., TEX. REV. CIV. STAT. ANN. art. 6701d (West 1977). (4) 2 KELLY, supra note 1, [section]113.15. (5) Renshaw 289 S.W.2d 621, 624. (6) Neese v. Dietz, 845 S.W.2d 311 (Tex. Ct. App. 1992), writ denied, May 5, 1993. (7) Renshaw 289 S.W.2d 621, 624-25. (8) Neese, 845 S.W.2d 311, 313. (9) R.W. RIVERS, TRAFFIC ACCIDENT INVESTIGATORS' HANDBOOK 155 (1980). (10) LYNN B. FRICKE, TRAFFIC ACCIDENT RECONSTRUCTION 62-13 (1990). (11) Id. at 62-14; RIVERS, supra note 9, at 157; TRAFFIC INSTITUTE, NORTHWESTERN UNIVERSITY, HOW TO USE THE TRAFFIC TEMPLATE AND CALCULATOR 19 (1984). (12) Paul L. Olson & Michael Sivak, Perception-Response Time to Unexpected Roadway Hazards, 28 HUMAN FACTORS 91, 93 (1986). (13) Id. at 95-96. (14) Id. at 93. (15) Samford x,. Duff, 483 S.W.2d 517, 525 (Tex. Civ. App. 1972), writ ref'd n.r.e., Oct. 11, 1972, and reh'g of writ of error overruled, Nov. 22 1972; Thornton v. Campise, 459 S.W.2d 455, 461 (Tex. Civ. App. 1970), writ ref'd n.r.e., Feb. 17, 1971.
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Title Annotation:Auto Safety
Author:Felton, Dale
Date:Apr 1, 1995
Previous Article:Child restraint litigation: compensating the littlest victims.
Next Article:Cross-examining the accident reconstructionist.

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