Are You Safe to Drive?
I
AUTOMOBILE driver, know thyself! My friend Schwartz did n’t. Schwartz was driving his car along a two-lane concrete highway one day last summer. His speedometer wavered from 40 to 50, back to 45, up to 60, and down again as the road gently twisted, turned, straightened out, and crossed other highways through an undulating countryside. Sometimes Schwartz was passed by faster travelers; occasionally he passed machines not maintaining his gait in the course of the smooth miles. My friend was neither road hog nor speedster. He held his own private pace with due caution.
Finally Schwartz found himself behind a heavily laden truck. He decided to pass. Although he saw another car coming toward him, he thought there was ample time for him to get around. He stepped on the accelerator. He moved to the left lane.
He discovered in one awful moment that the approaching machine was upon him!
The crash involved all three vehicles. In attempting to avoid a head-on collision, Schwartz drove into the side of the truck. The truck careened madly into a ditch. The other automobile sideswiped Schwartz’s machine and tumbled end over end off the road on the opposite side. Schwartz’s car remained miraculously in the highway, twisted and bent, but upright.
My friend received painful lacerations from flying glass, and for weeks hobbled about with a badly sprained back. The driver of the car which had approached him, a girl of twenty, recently emerged from a hospital with a shortened left leg and disfiguring scars on her face and neck. The driver of the truck was lucky. He received no more than a bad fright and minor bruises.
Schwartz was not only heartbroken because of the accident (a wealthy man, he voluntarily settled a small fortune on the girl), but he was dumbfounded that such a thing could happen to him. True, he had occasionally found himself unexpectedly in tight places while driving, but he was not given to taking foolish chances. At the time of the tragedy he was in full possession of his faculties. The sun was not in his eyes. He was not lighting a cigar, nor was he especially preoccupied by business or other cares. Moreover, he had just passed a physical examination with flying colors for a man of his age.
Finally he heard of a place where he might discover the cause of his gross miscalculation in passing the truck. Like the victim of a mysterious disease who hurries off to the specialist in the distant clinic, Schwartz went to Ames, Iowa. There his difficulty was diagnosed; the true cause of his almost fatal error was isolated.
He was found to be a sufferer from a singular ocular defect, one of several which have an important bearing on safe driving. He has deficient depth perception. Thus he is unable to determine how far away objects are from him, and likewise unable to gauge the speed with which they approach. If Schwartz’s eyes had told him how close the girl’s car was and how fast it was coming, a pitiful tragedy would have been averted. The specialist in this case is neither a physician nor an oculist. He is a psychologist. As chairman of the Committee on the Psychology of the Highway of the National Research Council, he is conducting researches into the personal causes of automobile accidents. His ‘clinic’ is a laboratory at Iowa State College, where he is associate professor of psychology. His name is Dr. Alvhh R. Lauer.
In the course of a number of years Dr. Lauer has developed and selected a series of tests calculated to enable him to determine whether or not a person has the physical attributes to make a safe driver. The tests are complete now, or practically so, and the psychologist is validating his methods by testing drivers whose accident records are known. So satisfactory have been the results that he is assured that in nine cases out of ten he can find out in thirty or forty minutes as much about a man’s ability to drive safely as one could discover formerly by the excessively tedious and costly practice of letting him operate an automobile for four or five years, counting the accidents he has experienced, analyzing them for the causes, and thus determining his relative proneness to mishap. The driver in the corps of the United Motor Coach Company of Des Plaines, Illinois, for example, who recently received the highest rating in Dr. Lauer’s tests was the driver with the best accident record in the fleet.
The day is coming when these tests will supplant the limited ones now being administered in the states which examine drivers before licensing them to drive. It is a practical certainty that progressive operators of large fleets of motor vehicles will soon be employing them in selecting their drivers. And they will enable insurance companies to determine more equitably liability and property damage rates. At the present time the safe driver pays for a large share of the carelessness and weaknesses of the poor driver — a system which certainly does not encourage good driving. Perhaps before long some automobile manufacturer will make the tests available to anyone who wants an analysis made of himself so that he can learn his own deficiencies and compensate for them. Then a driver will be able to know himself as Schwartz and thousands like him did not, and the number of tragedies on our streets and highways will be reduced.
‘But,’ one may well ask, ‘is it possible to test a man and then say whether or not he will have an accident?’
Since I asked the psychologist this question, I shall give his answer.
‘No, we can only determine whether or not the man is a safe “risk,”’ he said. ‘When a person is examined for a life insurance policy and it is found that he is suffering from tuberculosis, the company actuaries, with all the thousands of longevity records available, cannot tell when the man will die. Maybe he will die to-morrow; maybe he will live thirty years. The actuaries know merely that in the light of experience the victim of this disease is a poor risk, and the policy is denied him.
‘It is the same with susceptibility to accidents. If the probationer is color-blind, if his depth or distance perception is poor, and if he is inclined occasionally to take long chances, we cannot say that he will have an accident if he operates an automobile. But we can say that he is an exceedingly poor risk and that for his personal safety and for the safety of the public he should not be permitted to drive unless he is educated to correct his faults and to compensate for his deficiencies. And even then he should be allowed to drive only after he has assumed full responsibility for his driving.’
II
Dr. Lauer’s tests include twelve of vision (‘eye-openers’ to the layman), one of strength of grip, one of speed of movement, one of excitability, and a cover-all test of observation, motor control, nervousness, and manipulation.
While this last test is by far the most spectacular, the most surprising are the tests of vision. Twelve of them! Good vision means acuity only to most people. If Smith can read the legend on the distant billboard as well as Jones, he assumes that his sight is just as good; ergo, in the matter of eyes, he ought to be just as competent a driver as his friend. A few people go further than this and admit that color vision is probably of importance in driving. Again, if Smith can distinguish colors about as aptly as Jones, he is very sure indeed that his friend has nothing on him when it comes to adequate vision.
‘But what,’ inquires Dr. Lauer, ‘about your field of vision? What about this thing called depth perception? What about exophoria, esophoria, hyperphoria, strabismus, and lacunæ or scotomata?’
‘Never heard of any of ’em,’ answers Smith.
‘How about your susceptibility to glare?’ the psychologist goes on.
The bewildered Smith cannot cope with such an onrush of technical erudition. It is the scientist who must explain these strange things and what bearing they have on safe automobile driving. Not that Smith is stupid. No. Like most laymen, he is simply unaware of what efficient human eyes can do — and equally oblivious of the hazard that inefficient eyes represent.
Take field of vision, for example. A person with normal sight can look straight ahead as through the windshield of his car and yet, without altering the focus of his eyes, detect a moving object at either side. This gives him a total field of 185 to 195 degrees. The importance of a wide field is at once apparent. It enables the driver to watch the road and still see everything that comes toward him from the side. The person with a contracted field wears, in effect, ‘blinders.’ He does n’t see the car which is passing around him until it is in front of him. He does n’t see the machine which approaches at a fast clip at an intersection. He misses road markers of all kinds, including caution signs. He fails to see many things that he ought to see for his own safety and the safety of the people riding with him — not to mention the safety of other drivers and pedestrians. Sufferers with an extremely contracted field are said to have tunnel vision. It is as if they were looking through a tunnel or pipe and saw only what was at the far end.
Dr. Lauer has found that a field of vision of less than 140 degrees is dangerous. He measures the field by placing a large cardboard protractor in a horizontal position in front of the driver’s eyes with the centre of the flat edge at the bridge of the nose. While the driver’s gaze is focused straight ahead, the psychologist moves a pencil along the curved edge of the protractor from front to back until it passes out of the driver’s sight. He does this on both sides and the points of disappearance give the measurement of the field. The reader can test his own field of vision by focusing his eyes on some object directly before him and wiggling his fingers at each side of his head. The result will not be accurate, but at least he can discover if his field approximates the normal.
It is said that American Indians knew that the periphery of vision is more sensitive to movement than the centre of the eye. The Indian would lie on his back and look out of the corner of his eye to detect slight movements of bushes where enemies might be lurking.
Depth perception is equally important, but it is more interesting. Sufferers like my friend Schwartz cannot see depth or distance, A normal pair of eyes each focused on the same object gives a person three-dimensional sight. People with only one eye see depth very poorly. Close one eye and bring your two index fingers together at an easy distance. See how far you miss.
For this test the psychologist uses an old-fashioned stereoscope, such an instrument as everybody’s grandmother used to have in her front parlor, with a series of specially adapted pictures. He advises the driver with faulty depth perception to be exceedingly careful when he passes other cars, because an oncoming machine may be closer than he thinks.
While the reader knows whether he is rightor left-handed, is he aware that he also is rightor left-eyed? Probably not. And yet exact equality of sight is about as rare as ambidexterity. Psychologists call this common tendency ocular dominance. When the sufferer is fatigued, he unconsciously tends to use his better eye and to allow the other one to rest. In extreme cases the driver is, for all practical purposes, one-eyed, with an exceedingly narrow field of vision and impaired depth perception. To make it worse, the good eye is overworked and the strain causes headache and other disturbances, all of which result in still greater fatigue.
Dr. Lauer uses an odd device for determining ocular dominance. It is a metal instrument in the shape of a flattened cone. The driver being tested looks with both eyes through the large end, and the examiner moves a pencil back and forth not far from the other end. The driver is required to focus on the pencil. If he focuses on the pencil to the right of a centre sight on the instrument, his left eye is dominant, and vice versa. If he focuses on it at centre, he has used both eyes equally. Cross-eyed persons, who technically suffer from strabismus, use one eye almost exclusively. They are hampered all the time by the same difficulties that sufferers from ocular dominance experience at times of greatest fatigue.
Closely allied to strabismus are the three phorias. In exophoria, the eyes tend to turn out; in esophoria, they tend to turn in; in hyperphoria, one eye tends to turn up. In extreme cases, as I have said, the patient is called ‘wall-eyed’ or ‘cross-eyed’ or ‘cockeyed.’ But usually the defect is only a tendency and is not noticeable; indeed, the sufferer himself is ordinarily unaware of it. The danger is that the malfocus sometimes results in double vision.
A railroad engineman, recently tested, was of the opinion for years that there were two signal arms at all switches, one above the other. His was a case of hyperphoria. The sufferer driving an automobile, particularly at night, is in a dangerous predicament indeed. Especially is this so in cases of exophoria and esophoria. Instead of one, he sees two automobiles approach and does n’t know which to miss! He sees two tail lights on the car ahead.
If two cars are coming almost abreast, he sees the road filled from edge to edge with eight headlights forming a blurred, confusing mass.
III
A novel device is used by Dr. Lauer for testing resistance to glare. Called a glarometer, it consists of a light behind a circular, frosted glass and a diffusing lens. In the centre of the glass is the word ‘out’ (any word would do), printed plainly on a white background which is impervious to light. As the intensity of the light is gradually increased, the probationer is asked to tell when the light is so strong that the word disappears. For some people the word is gone when the light reaches only moderate intensity. Others can read it when the light is blinding to the ordinary sight. Since the intensity of the light is calibrated, it is possible to give each driver a definite rating on his resistance to glare.
Glare is a direct cause of some accidents and an indirect cause of others. In thousands of accidents each year the motorist gives ’blinded by headlights’ or ‘blinded by the sun’ as the sole reason why he failed to see the other car or the defenseless pedestrian in his path. As an indirect cause, glare from bright sunlight results frequently in dangerous fatigue; indeed, drivers who are unusually susceptible to glare have fallen sound asleep at the wheel. Being blinded by bright light has always been looked upon as the perfect excuse in case of an accident — but will it be considered so when drivers have an opportunity to know their eyes? Dr. Lauer advises those who are easily blinded to shield their eyes against sunlight by shaded spectacle lenses and against headlights by colored panels or disks on the windshield.
For color blindness he uses the Ishihara test, about which a great deal has been written. It consists of a series of circular areas made up of a patchwork of different-colored dots so arranged that one numeral in colors is visible to the normal eye while a different one is apparent to the person suffering from color blindness. There are many charts of different sets of colors in the series, so that it is possible to determine just which colors the driver cannot distinguish. In automobile driving, red-green color blindness is the most important because of the use of these colors in signals, and this combination of color blindness is the most common. Dr. Lauer, who has tested thousands of pairs of eyes, says that 10 per cent of male drivers and 1 per cent of female drivers are color-blind and that a tenth of these experience serious difficulty in reading signals. Thus there are thousands of drivers on the streets to-day who do not know what signals mean. Drivers in this category are cautioned to watch what other drivers do at signalized intersections and thus to compensate as best they can for their deficiency. It is not safe to memorize the relative positions of the red, amber, and green lights, because in some signals the green is at the top and the red is at the bottom, while in others the opposite is true.
A surprisingly large percentage of people do not know that there is such a defect as color blindness. Dr. Lauer tells a story about a man and wife who almost came to blows in his laboratory during the color-vision test. One of the Ishihara charts was shown to the husband, a commercial driver. He promptly said ‘21,’ which was the number color-blind people see on that particular chart. His wife, standing near by, saw the number 74, which is what normal eyes perceive. A bitter altercation ensued. The husband insisted that the number was 21, the wife that it was 74; then both appealed to the psychologist. Very carefully he explained the difficulty to both of them. But the wife was unimpressed. ‘No,’ she exclaimed. ‘Joe’s just bull-headed. Don’t pay any attention to him. He’s always that way when he’s around strangers.’
A thoroughgoing test for acuity of vision is also included in the series of examinations — the test which most people think of as being the only practical one of vision. In defense of those who hold this opinion let me say that it is the only test in use to-day (except for color vision) in most of the states which attempt to test the sight of drivers before granting them a license to drive. Acuity is, of course, very important. The psychologist tests the eyes together and each eye separately, both with and without glasses, if the probationer wears them. The studies have shown that 25 per cent of drivers wear glasses, a fact that has no particular significance from the point of view of traffic safety; but the studies have also shown that a considerable percentage of people who need to wear them do not, a fact that has a tremendous bearing on safety.
Some drivers have as low as 15 to 20 per cent of normal vision. This means that they can see at a distance of fifteen to twenty feet what the average person can see with equal clarity at one hundred feet. Some suffer from myopia or nearsightedness; others from hyperopia or farsightedness; and still others suffer from astigmatism, which means roughly that they are both farsighted and nearsighted in the same eye and have blurred vision. Except in extreme cases, farsightedness is the least dangerous of these defects.
Another not uncommon ocular difficulty is malingering of the eye, or its failure to function at certain times. Eyes frequently fail when they are needed most! And, curiously, this seems to be a purely psychological phenomenon. Lacunæ or scotomata also are found in a considerable percentage of cases. Everybody has a blind spot (of which he is not aware), but the sufferer from lacunæ has a blind spot so large that a child may be standing in full view a few hundred feet away and yet be invisible. A cheiroscope is used for detecting this condition — an interesting instrument. The probationer looks through the instrument with both eyes. With one eye he sees a simple picture, which he is asked to draw, and the other is trained on a plain piece of paper. Thus with one eye he is to draw what the other eye sees. If he is a sufferer from lacunæ and has a ‘hole in his vision,’ he will see and be able to draw only the portion of the picture seen by the defective eye. Both eyes are tested this way in turn.
IV
When the tests of vision are completed, the examiner can say with fair accuracy whether or not the probationer’s vision is adequate for safe automobile driving. But vision is not all there is to the physical attributes of a safe driver. The tests of sight do not exhaust Dr. Lauer’s bag of scientific tricks. There is strength of grip, for example, which is very important because of the power required to hold an automobile in the road in case of a blowout of a tire or to swerve the car suddenly to avoid a collision. Some women drivers are scarcely strong enough for driving certain types of cars, and truck and bus drivers need powerful hands to control their heavy vehicles even though ordinary manipulation may be comparatively easy. A dynamometer, or spring device like a small pair of scales, is used to test grip; for safety each hand should have a gripping strength of from 75 to 100 pounds.
Speed of movement is measured by the use of a telegraph key and an electric counter. The person taking the test operates the key as rapidly as he can in five periods of ten seconds each. His score is found by averaging the number of contacts made, and the record is compared to the normal. Quickness is so often vital in automobile driving that the importance of this attribute to safe driving is obvious. This test is similar to a standard test for reaction time, but is more practical because it is not influenced so much by distractions to the person taking it.
A complicated electrical device including a Wheatstone bridge and a galvanometer is used to measure the driver’s susceptibility to sudden noise, which, in turn, gives a clue to his nervous stability. First used in France to select street-car motormen, the method is the same in principle as that of the famous ’lie detector’ which is rapidly coming into use by progressive criminologists. A tiny electric current is passed through the body of the person being tested. Suddenly a loud automobile horn is sounded near him. If he is unstable nervously, his body resistance to the current is lowered and this is registered on the galvanometer. The unexpected sounding of the horn will give one man a terrific start, while another apparently would show no loss of composure if a bomb were to be set off under his chair.
Dr. Lauer will add an audiometer to his equipment when funds become available. A well-known device, it measures accurately a person’s ability to hear. It varies the pitch and sound intensity so that hearing in the various registers is measured and calibrated. The psychologist says that, while hearing is undoubtedly important to safe driving, research studies to show exactly how important it is are yet to be made.
By far the most interesting piece of equipment developed by the psychologist is a mechanical device for giving a driving examination which tests the driver’s observation, motor control, nervousness, and manipulation. Since an actual driving field, with all the common turns and stops carefully arranged (such as Dr. Lauer has laid out near his laboratory at Ames), is not transportable, an amazing substitute has been developed. The man being tested sits at the wheel of a dummy car. It has the regulation steering wheel, horn, pedals, gearshifting lever, and accelerator. He looks through a windshield and over the top of a dummy hood, but, instead of seeing a roadway, his gaze enters a miniature stage about four feet wide, two feet high, and three feet deep. Across the front of the stage several inches from the floor is a quarter-inch iron bar, and to this bar is fixed a toy automobile. The driver turns the wheel of the dummy car to the right, and behold, the toy car moves along the bar to the right. He finds that he can move the toy back and forth along the bar at will.
The floor of the stage consists of an endless leather belt operated by a special electric motor. On the belt is painted a country road with trees, fences, barns, houses, filling stations, and railroad tracks. The road winds, branches, comes to intersections, goes straight — it does, in fact, about everything that an actual road can do. Since the belt moves from back to front, it passes under the toy car, giving the same effect as if the toy car were passing over the road. Part of the task for the person taking the test is to steer in such a manner that the toy car will be directly over the right side of the road as the road moves under.
If all ono had to watch were the road and the steering, it would not be so difficult a test. But that is by no means all. At the back of the stage such signs as ‘Slow down and sound horn at 6,’ ‘Take road to left at 8,’ and ‘Observe railroad at 4’ appear in rotation, and corresponding numbers, which represent road signs, are painted along the side of the road. One must follow these directions and one must also observe a small Stop-and-Go signal situated at the top of the stage.
But still I have not fully described this unusual contrivance. The speed with which the road moves is determined by the pressure the driver puts on the accelerator. And as he shifts gears from low to high the road speeds up, giving, of course, the illusion that the toy car speeds up.
Thus the person taking the test must keep the toy car over the right side of the road as it winds through the makebelieve countryside. He must observe the Stop-and-Go light at the top of the stage and follow the directional signs at the rear. Such errors as not heeding the signals and signs are counted by the examiner, who sits in the driving seat of the dummy car with the driver. An automatic check is made of the driver’s ability to keep the toy car in the road by silver springs suspended from the bottom of the car, which contact copper lugs set at short intervals on the road. If he gets off the road, contact is not made. As one who has taken this test, permit me to say that it is not easy.
But its scientific worth has been demonstrated. The alert, capable, observant, quick, cool driver comes through with the best record almost invariably, and these are the characteristics found in the best and safest drivers on our highways. In fact, higher correlations are obtained between the score for this test and actual accident records than between employer’s ratings, after several years’ service, and the records. In other words, it is a more accurate test than actual driving for several years.
The work is not finished (few scientific researches of this kind ever are), but a magnificent start has been made. Dr. Lauer is constantly improving his technique and his equipment. He hopes eventually to be able to classify every driver — and not just nine out of ten, as he is now able to do — as safe or unsafe, and to tell the unsafe drivers just wherein they fail to meet the standard. Without doubt he will accomplish this. The advantages will be manifold. The operators of fleets of cars and state motor vehicle commissioners will be able to keep off the highways drivers who lack the requisites for safe driving, and thoughtful people will be able to determine their own deficiencies and either compensate for them or cease driving voluntarily for their own sake and for the sake of the public. A driver will really be able to know himself!