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Similarly, using only social maladjustment based on such items as a broken home, truancy, poor employment records, marital discord, and repeated contacts with social service or public health agencies, McFarland and Mosely were able to classify,truck drivers as accident-free or repeaters, with an accuracy of 85 percent. Thus by sampling attitudes, psychopathology, social maladjustment, and past driving records, strikingly accurate predictions of high and low accident rates can be made.


If accidents result from mere chance, then taking into account the difference in traffic volumes, the ratio should be independent of the time of day. However, the accident ratio is greater at night. Furthermore, there are more accidents per vehicle mile in the four hours after midnight than within the four hours preceding Cars and roads remain unchanged. Faulty driving is the primary cause.

Surveys of broad population groups show, on a mileage basis, that there is a much higher degree of accident involvement among the young. Youthful male drivers have a death rate from accidents that exceeds any other. Many studies show that accident involved drivers tend to be psychologically maladjusted. Dangerous drivers are more likely to use driving as an outlet for tension. Because of anti-social attitudes, they have far more than average contact with the courts and social welfare agencies. The importance of driver psychopathology in accident causation has been verified by predictive studies which demonstrate a much higher accident rate among poor credit risks and people hospitalized for suicide attempts.

There is another tragic proof that driver fault, not chance, is the main cause of traffic accidents. Alcoholics and other problem drinkers, who drive after excessive consumption of alcohol, are involved in 25,000 deaths and 800,000 crashes each year. Considering the combined experience of psychological misfits and excessive drinkers, it is apparent that a small proportion causes more than half of our serious traffic accidents.


The day by day deterioration of motor vehicles on the nation's highways poses an excessive and unnecessary safety hazard. Broad countermeasures are required involving vehicle manufacturers, owners, distributors and dealers, and inspection and servicing personnel. Deterioration due to age involves rusting, rubber oxidation, and metal fatigue. Motor vehicle inspection statistics indicate that about 59 percent of the vehicles which are six years and older have been rejected." Especially shocking is the finding that cars one year old or less were rejected at a rate of 25 percent.

These figures are conservative when compared with the findings of the Automobile Club of Missouri diagnostic clinic.25 Potentially dangerous defects were identified on 50 percent of then-current cars (1968s). The figure rose to 90 percent on cars five years old. The most common defect was in wheel alignment, as measured by camber and toe-in. Brakes came next on the list.

Zero defect is the only acceptable level of performance in a vehicle used on highways. Thus, it is important to determine the proportion of highway accidents caused by mechanical malfunction. If most accidents are caused by vehicles veering out of control because of defective parts or tire blowouts, what difference can driver behavior make? Indeed, some speculate that concentration upon the responsibility of purchasers and operators of motor vehicles may detract from the responsibilities of those who manufacture and sell them.

Tire Failure

How important a factor are flat tires in causing automobile accidents? To answer this question, a study was made of tire malfunction and accidents on the Illinois Tollway. The cooperative project included the Traffic Institute of Northwestern University, the Illinois State Toll Highway Commission, the Illinois State Police, and the Rubber Manufacturers Association. The project director was J. S. Baker. There were 1,486 recorded auto accidents on the Illinois Tollway from September, 1966 to August, 1967. No more than 36 (2.42 percent) and possibly as few as 13 (0.88 percent) of the accidents followed flat tires. This was between one in 40 and one in 110 auto accidents on the tollway. On the average, automobiles had a flat tire for every 22,000 miles traveled. At least 99.94 percent of the drivers during the test period coped successfully with an estimated 60,000 flat tires on the tollway. Only one in 1,700 (.06 percent) to 4,600 (.02 percent) flat tires was followed by an accident. (The range of percentages was caused by incomplete evidence. After some accidents it was impossible to interview the persons or to locate the tires involved.) Experts studied the accidents in which a tire was deflated for any reason. Careful attention was given to drivers' explanations of the accidents. Whenever possible, damage to tires, rims, and autos was examined in detail. The purpose was to determine how many flat tires had been disabled before the accident, thus perhaps contributing to it.

Baker said that drivers often blame accidents on physical factors such as tires, wrongly assuming that a tire went flat before rather than during an accident. Drivers also appear to blame about two and one-half times as many accidents on tire malfunction than is justified. Tollway police accepted about two out of three of the drivers' explanations. An intensive follow-up study showed that a minimum of five percent and a maximum of 15 percent of the vehicles could have had the flat tire before the accident.

This study showed that tire failure caused only between one and two and one-half percent of the accidents on a high speed freeway.

New York And Pennsylvania Studies

Other studies of actual highway accidents reveal the proportion of accidents due to all forms of mechanical failure. Unless there is some obvious reason to think otherwise, police officers tend to report what drivers say cause accidents.20 Driving while intoxicated is illegal and can lead to severe penalties. Drivers tend to cite vehicle failure as a primary cause rather than driving under the influence of alcohol or severe fatigue. In 1968, on the New York State Thruway, there were 5,031 accidents. From 703 accidents listed as vehicle caused, 64 are attributed to either an insecured load or a defective trailer hitch. Following is a breakdown of the 639 accidents which can be attributed to vehicular failure:

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For the above reasons, Fisch believes that mechanical failures are not under-reported by the special state trooper detail assigned to the Thruway. About half of the defects are attributed to tires. Judging by the results of the Illinois study, detailed tire inspections would have yielded a lower figure in the Thruway results.

The necessity for detailed in-depth investigation of accidents by various disciplines has long been recognized by highway safety engineers. Perhaps the first large scale project along these lines has started in Pennsylvania.27 Eleven investigating teams including an engineer and a state patrolman, supported by a physician and an automotive expert were established. To date, 219 accidents have been investigated. Preliminary results indicate that mechanical defects were definitely involved in only 18 of these accidents, for a total of eight percent. 28 Although the preliminary nature of these findings must be stressed, they are consistent with other appraisals of the New York Thruway accident statistics.

It should be emphasized that the above studies do not, in the least, negate the importance of eliminating injuries and deaths due to mechanical defects. As in the case of improved vehicle design to minimize human destruction after impact, correction of mechanical defects should pay off rapidly with practical results.

Highway defects also cause accidents. A dropped shoulder can throw a vehicle out of control. Many older highways have unexpected obstructions or sharp changes in alignment. The failure to warn of such a hazard may place a driver in a dangerous situation with possible tragic consequences. Even more deplorable are the highway hazards which are to be found on new interstate highways. These perils include unprotected bridge piers, unnecessary signs, and improperly placed guard rails - items which are only a few of the many dangerous objects which confront the motorist who has the misfortune to leave the paved travel lanes. The transcript of the vital Blatnik Committee hearings on this subject runs over 1200 pages and is filled with horrible examples of how not to design or build highways.“


Vehicle de fects cause only a small proportion of highway accidents. But even with this small percentage, several thousand people are killed and many times that number are injured because of the negligence of others. There is no excuse for careless automotive safety inspection or faulty maintenance. There is equal need for a concentrated attack on highway deficiencies. The Federation of Insurance Counsel, in its publication entitled "Booby Trapped Highways," has illustrated faulty highway design splendidly. To a traffic engineer, it is tragic to realize that a group of attorneys must point out that virtually each of these hazards could have been eliminated had published safety policies and procedures been followed.

A particular person or group is responsible for each vehicle and highway defect. There is a distinct need to sharpen the focus of causative responsibility on those individuals and organizations upon whose actions the safety of others depend. The proposed no-fault system would abolish the existing legal foundation of responsibility. This would be a grave mistake. Instead, means should be sought to improve existing fault seeking machinery. There surely must come a time when it no longer can be said, "For want of a traffic sign, a human life was lost."


Except for a person contemplating suicide, nobody wants to injure or kill himself. It seems logical that fear of injury or death would be the paramount factor in driving behavior. It might there fore be reasonable, as Keeton and O'Connell aver, to believe that change in law would not diminish the major deterrent value of fear of injury to oneself. But before we bow to this seemingly inviolable "law" of human logic, it would be wise to examine the antecedent of a major injury accident.

The Top Of The Accident Pyramid

Heinrich, when writing about industrial accidents, points out that all accidents must be considered in accident prevention analysis." Accidents not injuries - are the proper point of attack. The terminology "major or minor accidents" is misleading. In one sense, there is no major or minor accident. There are major and minor injuries. It may be said that a major accident is one that produces a major injury. The accident and the injury are, however, distinct occurrences; one is the result of the other. When the terms "accident" and "injury" are so merged, it is assumed that no accident is serious unless it produces a major injury. Yet thousands of accidents, having the potential of producing serious injuries, do not so result. There are certain types of accidents, of course, where the probability of serious injury may vary in accord with circumstances. A fall, if occurring on a level field of soft earth or on a rug-covered floor in the home, may not have so serious a potential as a fall of a steel erector from a skyscraper. Yet the former may, and often does, result in a severe injury.

Only the upper portion of the pyramid is visible in the case of automobile accidents. In 1967, according to figures gathered by the National Safety Council, only one out of every eleven accidents produced a fatality or a disabling injury beyond the day of the accident. The remaining ten out of eleven accidents are classified as property damage accidents which include non-disabling injury accidents. There is no record of the many un reported minor collisions which are not tabulated. For example, in New York State, reports of accidents having an estimated damage less than 100 dollars are not required.

Major Injury Accidents

When reconstructing many major automobile accidents I have found that frequently only the smallest of margins separates the minor accident from the major. Heinrich cites the following case which illustrates the close relationship between the minor accident and that which is fatal:

A millwright attempted by hand to put a 5 inch
belt on a revolving pully 24 inches in diameter.
Tight and loose pulleys were not provided, no belt
pole was used, the employee wore a loose jumper
with long sleeves and stood on a shaky stepladder
while slipping on the belt from the underside.
He was caught and killed. Investigation indicated
that this method of slipping on the belt had been
employed daily for several years. Review of first-
aid records for a period of four years disclosed 33

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