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Direction guidance of road vehicles. Are better controls in sight?
Applied l:.'rgonomics 1972, 3.3,136~141
Direction guidance of road vehicles. Are better controls in sight? Jaroslav Tejmar Formerly Visiting Professor, University of Geneva, Switzerland Several types of car steering control were tested experimentally. The preferred solution seems to lie in the direction of progressive steering. In the middle-range, the relation of input at the steering-wheel to the output at the steered pair of car wheels is approximately the same as w i t h current cars, but towards the left and right extremes the car wheels are turned more, thusfacilitatingparking manoeuvres. There are both advantages and disadvantages inherent in the present necessity for drivers to steer their cars by manual control. Proposals to replace this individual control by machine guidance (Fig 1), for instance by induction loops built into the super-highways of tomorrow, are quite realistic technically, but utopian from the economic and administrative points of view. Thus a substantial improvement in methods of manual guidance and control would be of human and commercial value.
Possible i m p r o v e m e n t s Criticism has been expressed concerning the existing steering elements or their parts (Shackel, Wilkes and Blake, 1958; Kroemer, t966; Coermann, 1968; Kirk, Edwards and Hindle, 1964; Hindle, Edwards and Kirk, 1964). Also, Grime (1958)has encouraged an overall reconsideration of all control elements in motor-cars. Although many 'backyard' experiments might be done, only one prominent manufacturer has really shown a new kind of steering (Wrist-Twist, Fig 2), and many others have improved only the most 'dangerous' part - the steering column.
performance, by the mechanism of regression to older habits of operation, especially, under fatigue and stress conditions. Thus improvements must be such that the user can cope wilh them under all circumstances.
Background to experiments The starting point for the experimental work was a chart of possible steering elements given by Coermann (1967, 1968) (Fig 3). It may be seen that, from the purely physiological point of view, some of those included are theoretical possibilities only. This holds true, for instance, for version (d), which would not enable a comfortable posture leaning back, and for (b) where the backrest would have to be narrow so as to allow the elbows to pass. In (g) there would be some difficulties getting into the seat, and in all positions where legs control the direction, the arms and hands would have to control velocity and braking. Again, with (1), fatigue of the relatively weak lateral muscles of the foot would not allow continued operation for long.
The orbital flight programmes have brought about some new ideas; for example, the torque controller, which gave superior performance under both static and vibration test conditions 03/eisz, Allen and Goddard, 1966), and also the high ranking pressure control (Ziegler and Chernikoff, 1967), suggested already in 1954 by Gibbs (Gibbs, 1954). However, caution is necessary if one is to transfer these results to the road user. When considering the possibility of new designs, we must remember that the present steering wheel shape serves as support for the forearms, also that changes of the steering system might give rise to confusion and bad Presented in part to the 4th International Congress of the International Ergonomic Association, Strasbourg, 1970. A detailed paper is in preparation: Tejmar, J., and Coermann, R. Untersuchungen iiber die optimale Gestaltung von Steuervorrichtungen fiJr industrielle FiSrdermittel, Project No 3666, Land NordrheinWestfalen, 1969 136
Applied Ergonomics September 1972
Fig 1 Electronically guided car for testing tyres upon a closed test-circuit (by courtesy of Continental Rubber Co, Hanover, Germany) 1. The electro-mechanical steering equipment 2. The control and programme set 3. Radio transmission of the values measured
Fig 2 Wrist-Twist experimental steering (Dunne, 1965). An improved version (1966) includes a newsteering ratio of 17-8 to 1; the small grips turn together with a twist of the wrist (Courtesy of Lincoln-Mercury Division, Ford Motor Co).
However, an arrangement (e) suggests the appealing possibility of combining the directional guidance with acceleration control (pulling backwards) and braking (pushing forwards) in one single element. With the exception of (a), of course, all arrangements show much shorter movement required to operate the input element. This recalls the replacement of tiller-steering at the beginning of tiffs century (Schreiber, 1914), with its limited operational angle, by the steering-wheel which reduced the power required.
Outline of experiments With the late Dr. R. Coermann as the senior experimenter, some of these arrangements were tested using equipment designed in 1966 mainly by K.H.E. Kroemer (by courtesy of the Max-Planck-Institut f'dr Arbeitsphysiologie, Dortmund, Germany, and under grants from the Deutsche Forschungsgemeinschaft and Land Nordrhein-Westfalen). The equipment for the experiments is shown in Figs 4, 5 and 6. The subject sits facing a screen, and a line moving downwards, wandering from side to side, is projected onto it as the test 'road'. The subject's task it to steer a spot of light from side to side only, at a fixed level, to keep it on the 'road' all the time if possible. The different types of steering controls used in the tests are shown in Figs 7 to 10. In each test, two control types were tested against each other and always in both
sequences of arrangement, in order to rule out the influence of fatigue from the first part upon the second, which followed after a rest of 60 minutes. The test runs lasted 80 minutes in each case, and during this time 3600 readings were taken. Twenty subjects (12 men and 8 women), who with two exceptions were students aged 18 to 26, participated in 160 experiments after having practised in 4 to 8 sessions, similar to the experiments. The participation in different control pairs was carefully randomized, so that individual subjects participated in different control pairs in successive sessions, imitating the mixed population of drivers in practice. There was only one exception from this rule - ladies performed only within control pairs of low and middle resistance (thin and interrupted lines of the symbols in Table 1; the thick lines show high resistance). Not all people did the whole cycle of control pairs and they were substituted by other subjects. Tile average number of 3600 checks of errors were processed by a computer. The arithmetical means of errors thus obtained for bothparts of the control pair were tested by Wilcoxon non-parametric test. Different levels of significance occurred with different control pairs, as well as contradictions in the merits of the individual arrangements of controls with different subjects. To obtain an overall statement about the rough tendency in favour/unfavour of the individual arrangements, we had to establish a further synthetic index, constructed Applied Ergonomics September 1972
137
I Curve to left ~
Curve to right "-~'1 i
I S . , I ~,
0
I
b}
(c)
(d)
(~)
(f)
(g)
(h)
(i)
(j)
(k)
(t)
(o)
9
Fig 3 Possibilities for new steering elements (Coermann, 1968) (by courtesy of S. Karger, Basle - New York)
in tile following manner. For every preponderance of errors within a test pair of controls with no statistical significance, we charged one negative poin!; for those of P .05, two points, for P .01, four points, and for P .001, eight negative points. The sum of the 'penalty' points gives the virtues of the arrangement, and vice versa. To enable a general comparison of tile differences obtained between the control types tested, the averaged scores are combined in Table 2. However, since these scores are combined from different tests with diiTerent subjects, they can only be taken as a guide to the general differences between controls and not as a precise
Fig 4 Overall View of the testing device used at the Max-PlanckInstitute for Work-Physiology at Dortmund, Germany. A film projector, projecting the test'road' B the film loop of 7.5 m length C galvanometer giving the light spot for tracing the test 'road . . . . D the test-driver's seat, here with steering wheel arrangement E1 potentiometer feeding the deviations of the steering element into the registration system E2 compensating potentiometer assuring the zero level at the beginning of each run F digital voltmeter G tape drum delivering the tape for punching with instantaneous characteristics of the 'road' and of deviations fed in by the steering component 138
Applied Ergonomics September 1972
41
0
Fig 7 Arrangement with a steering wheel. Several modifications were tested, the steering angle and resistance being changed: 90 degrees from medium line to extreme left or right, and high resistance 90 degrees and medium resistance 180 degrees and medium resistance 180 degrees and low resistance 360 degrees (i e, one full turn to each side) and low resistance Other combinations were shown to be unrealistic
I;
Fig 5 Projecting screen with photo-elements reading the codes pertinent to each picture of the 'road' and feeding them into the tape
ISr
2"~
I
0
100
200
3?5
500
600
750
Fig 6 A part of the test 'road' showing the digital characteristics of the position of the dark spot, which in reality was the beam of the controlled galvanometer C in Fig 4. The task of the test subjects was to hold this beam and the light spot as precisely as possible upon the 'road' by moving it only from side to side, the horizontal level being fixed by the system at ]/3 distance up the display from the bottom. At the right, the BCD-code is marked on every picture, but is invisible to the test subjects; it is read by the photo-elements in Fig 5
Fig 8 Arrangements with compounded side-levers. The light spot moved towards the depressed lever; the other lever went up simultaneously, thus allowing operation by one hand only. Theoretically, 90 ~ of lever movement was possible, but in practice this was limited to 60 ~ because of the restriction on the arms by the seat rest and partly because of the inconvenience in bending forward too far.
Applied Ergonomics September 1972
139
: .J ".,
\,
Fig 10 Arrangement with compounded pedals pushed from body-near position (right leg - right margin of the screen) to body-far position (right leg - left margin), and vice-versa
Fig 9 Arrangement with one central joy-stick moved from side to side - concommitant with the direction of the light beam
measure. Therefore only the large differences shbuld be considered. For example, the highest number (147) shows that in not a single pair of experiments was the pedalling arrangement superior to the steering-wheel with medium movement of 180~ and medium resistance which, in general, was the best condition.
Table 1 Scores derived from all comparisons for each control pair tested Pair of controls tested * First Wheel, Wheel, Wheel, Wheel, Wheel, Wheel,
Control tested first
Second 90, high 180, medium 180, medium 360, low 90, medium 180, low
34 21 12 36 20 25
9 28 41 10 16 18
Wheel, 90, high Side lever, 60, high Wheel, 90, medium Side lever, 60, medium Wheel, 90, low Side lever, 60, low
25 9 20 2 30 1
27 56 22 60 8 66
Wheel, 180, medium Joystick-- high
Joystick-high Wheel, 180, medium
5 38
43 11
Wheel, 180, medium Compounded pedals-high
Compounded pedals-high Wheel, 180, medium
0 73
74 0
Side lever, Wheel, 90, Side lever, Wheel, 90, Side lever, Wheel, 90,
60, high high 60, medium medium 60, low low
Wheel, Wheel, Wheel, Wheel, Wheel, Wheel,
180, medium 90, high 360, low 180, medium 180, low 90, medium
Control tested second
Scores assigned according to the significance of the difference found between the given controls from each control pair test
Significance Not significant P = 0.05 P = 0.01 P = 0.001
Score 1 2 4 8
* Each case gives type of control, number of degrees of movement on either side of the 'straight ahead' position, and the level of resistance to movement 140
Applied Ergonomics September 1972
Table 2 Combined error scores for comparison of control types tested Control type *
Wheel, Wheel, Wheel, Wheel, Wheel,
Combined error score
180, medium 90, medium 180, low 90, high 360, low
17 31 41 49 77
Side levers, 60, medium Side levers, 60, high Joystick - high Sidelevers, 60, low Compounded pedals-high
80 81 81 96 147
* Each case gives type of control, number of degrees of movement on either side of the 'straight ahead' position, and the level of resistance to movement
The results did not completely meet expectations as it was supposed that the precision of tracking would be highest with the steering-wheel having 45 ~ turn to the right and 45 ~ to the left. Apparently, with an apparatus of some mechanical resistance, the proprioception in subjects without a special and probably prolonged training did not allow the response required to avoid overshooting the trace. With apparatus of more precision, the optimum might perhaps be shifted more to the steering with limited rotation, but Katz (1925) has already shown the necessity for the driver to 'feel' the road through the steering element. Everyday experience underlines the importance of this observation. Conclusion
The method adopted, an up-to-date modification of the classical approach of Graf (1931, 1932), certainly does not allow an uncritical transfer of the experimental results in detail to the practical conditions of heavy roadtraffic. Nevertheless, the losses upon roads and the loads imposed upon drivers are rising instead of being reduced, and only the sum of many improvements in the lay-out of roads, signals, cars and their single elements, not to forget better training of drivers, gives some chance for the future. If we are to offer some recommendations from our experiments, the first one would be the reduction of the turns upon the steering-wheel necessary for the change of dkection, but not to such a degree that the smallest movement of the steering-wheel - in the hands of an average driver - would result in a considerable deviation. On the other hand, during parking manoeuvres and going at low speed round the sharp corners of city streets, a large deviation of the road wheels should result from a relatively small displacement of the circumference of the steering-wheel in order to make these operations faster and easier, especially for female drivers. These two requirements can be fulfilled only by progressive steering with a differential ratio of steering input to steering effect. Such a system has been made and successfully tested by Grossbach (1967).
References
Coermann, R. 1967 World Congress for Automotive Medicine, May 7 13, Vienna. Gestaltung yon Kraftfahrzeugen nach ergonomischen Gesischtspunkten. Coermann, R. 1968 1st Int Seminar Biomechanics Zurich, 1967, 258263 (Karger, Basel/New York) Kinetische Probleme beim Fiahren von Kraftfahzeugen.
Dunne, J. 1965 Automotive Industries, Philadelphia, Pa., May 1, 6263.Ford's new steering system. Gibbs, C.B. 1954 Brit JPsycbo145, 24 - 39. The continuous regulation of skilled response by kinaesthetic feedback. Graf, O. 1931 Handbuch der biol. arbeitsmethoden, E. Abderhaden (ed.), Section IV, part 13, Urban & Schwarzenberg, Berlin - Munich - Vienna. Die Methodik des pharmakiologischen Arbeitsver suchs. Graf, O. 1932 Arbeitsphysiologie (Dortmund) 6, 169. ()ber den Zusammenhang zwischen Alkoholblutkonzentration und psychiescher Alkoholwirkung. Grime, G. 1968 Ergonomics 1.2, 151 - 162. Research on human factors in road transport. Grossbach, A. 1967 Private demonstration, patent pending. Hindle, T., Edwards, E., and Kirk, N.S. 1964 Design 189, 61 - 65. Motor car design and driving skill. Katz, D. 1925 Zschr. Psychol. (Barth), Leipzig, 270. Der Aufbau der Tastwelt, Erg~nzungsband 11. Kirk, N.S., Edwards, E., and Hindle, T. 1964 Design 188, 36 - 41. Designing the driver's workplace. Kroemer, K.H.E. 1966 Automobiltechnische Zeitschr 68.11,380 - 385. UngenU~ende Berncksichtigung arbeitsphysiologischer Erkenntnisse bei der Konstruction yon Kraftfahrzeugen als Unfallursach. Schreiber, A. 1914 Der Motorwagen, p 4. Ober linksseitige Steurung. Quoted by W. Lutter: Rechts oder links im Strabenverkehr, Res. Dept. Ministry of Traffic, Bonn, Germany, 1963, p 161. Shackel, B., Wilkes, E.G.M., and Blake, J.E. 1958 Design I 15, July, 29 - 35. Ergonomics versus styling in cars. Wcisz, A.Z., Allen, R.W., and Goddard, C.J. 1966 2nd Annual NASA-University Conference on Manual Control; MIT Cambridge (Mass.), NASA SP- 128. An evaluation of three types of hand controllers under random vertical vibration. Ziegler, P.N., and Chernikoff, R. 1967 Nav Res Lab Report 6646, 9 pp. A comparison of three types of manual controls on a third-order tracking task. Applied Ergonomics September 1972
141
Direction guidance of road vehicles. Are better controls in sight? Jaroslav Tejmar Formerly Visiting Professor, University of Geneva, Switzerland Several types of car steering control were tested experimentally. The preferred solution seems to lie in the direction of progressive steering. In the middle-range, the relation of input at the steering-wheel to the output at the steered pair of car wheels is approximately the same as w i t h current cars, but towards the left and right extremes the car wheels are turned more, thusfacilitatingparking manoeuvres. There are both advantages and disadvantages inherent in the present necessity for drivers to steer their cars by manual control. Proposals to replace this individual control by machine guidance (Fig 1), for instance by induction loops built into the super-highways of tomorrow, are quite realistic technically, but utopian from the economic and administrative points of view. Thus a substantial improvement in methods of manual guidance and control would be of human and commercial value.
Possible i m p r o v e m e n t s Criticism has been expressed concerning the existing steering elements or their parts (Shackel, Wilkes and Blake, 1958; Kroemer, t966; Coermann, 1968; Kirk, Edwards and Hindle, 1964; Hindle, Edwards and Kirk, 1964). Also, Grime (1958)has encouraged an overall reconsideration of all control elements in motor-cars. Although many 'backyard' experiments might be done, only one prominent manufacturer has really shown a new kind of steering (Wrist-Twist, Fig 2), and many others have improved only the most 'dangerous' part - the steering column.
performance, by the mechanism of regression to older habits of operation, especially, under fatigue and stress conditions. Thus improvements must be such that the user can cope wilh them under all circumstances.
Background to experiments The starting point for the experimental work was a chart of possible steering elements given by Coermann (1967, 1968) (Fig 3). It may be seen that, from the purely physiological point of view, some of those included are theoretical possibilities only. This holds true, for instance, for version (d), which would not enable a comfortable posture leaning back, and for (b) where the backrest would have to be narrow so as to allow the elbows to pass. In (g) there would be some difficulties getting into the seat, and in all positions where legs control the direction, the arms and hands would have to control velocity and braking. Again, with (1), fatigue of the relatively weak lateral muscles of the foot would not allow continued operation for long.
The orbital flight programmes have brought about some new ideas; for example, the torque controller, which gave superior performance under both static and vibration test conditions 03/eisz, Allen and Goddard, 1966), and also the high ranking pressure control (Ziegler and Chernikoff, 1967), suggested already in 1954 by Gibbs (Gibbs, 1954). However, caution is necessary if one is to transfer these results to the road user. When considering the possibility of new designs, we must remember that the present steering wheel shape serves as support for the forearms, also that changes of the steering system might give rise to confusion and bad Presented in part to the 4th International Congress of the International Ergonomic Association, Strasbourg, 1970. A detailed paper is in preparation: Tejmar, J., and Coermann, R. Untersuchungen iiber die optimale Gestaltung von Steuervorrichtungen fiJr industrielle FiSrdermittel, Project No 3666, Land NordrheinWestfalen, 1969 136
Applied Ergonomics September 1972
Fig 1 Electronically guided car for testing tyres upon a closed test-circuit (by courtesy of Continental Rubber Co, Hanover, Germany) 1. The electro-mechanical steering equipment 2. The control and programme set 3. Radio transmission of the values measured
Fig 2 Wrist-Twist experimental steering (Dunne, 1965). An improved version (1966) includes a newsteering ratio of 17-8 to 1; the small grips turn together with a twist of the wrist (Courtesy of Lincoln-Mercury Division, Ford Motor Co).
However, an arrangement (e) suggests the appealing possibility of combining the directional guidance with acceleration control (pulling backwards) and braking (pushing forwards) in one single element. With the exception of (a), of course, all arrangements show much shorter movement required to operate the input element. This recalls the replacement of tiller-steering at the beginning of tiffs century (Schreiber, 1914), with its limited operational angle, by the steering-wheel which reduced the power required.
Outline of experiments With the late Dr. R. Coermann as the senior experimenter, some of these arrangements were tested using equipment designed in 1966 mainly by K.H.E. Kroemer (by courtesy of the Max-Planck-Institut f'dr Arbeitsphysiologie, Dortmund, Germany, and under grants from the Deutsche Forschungsgemeinschaft and Land Nordrhein-Westfalen). The equipment for the experiments is shown in Figs 4, 5 and 6. The subject sits facing a screen, and a line moving downwards, wandering from side to side, is projected onto it as the test 'road'. The subject's task it to steer a spot of light from side to side only, at a fixed level, to keep it on the 'road' all the time if possible. The different types of steering controls used in the tests are shown in Figs 7 to 10. In each test, two control types were tested against each other and always in both
sequences of arrangement, in order to rule out the influence of fatigue from the first part upon the second, which followed after a rest of 60 minutes. The test runs lasted 80 minutes in each case, and during this time 3600 readings were taken. Twenty subjects (12 men and 8 women), who with two exceptions were students aged 18 to 26, participated in 160 experiments after having practised in 4 to 8 sessions, similar to the experiments. The participation in different control pairs was carefully randomized, so that individual subjects participated in different control pairs in successive sessions, imitating the mixed population of drivers in practice. There was only one exception from this rule - ladies performed only within control pairs of low and middle resistance (thin and interrupted lines of the symbols in Table 1; the thick lines show high resistance). Not all people did the whole cycle of control pairs and they were substituted by other subjects. Tile average number of 3600 checks of errors were processed by a computer. The arithmetical means of errors thus obtained for bothparts of the control pair were tested by Wilcoxon non-parametric test. Different levels of significance occurred with different control pairs, as well as contradictions in the merits of the individual arrangements of controls with different subjects. To obtain an overall statement about the rough tendency in favour/unfavour of the individual arrangements, we had to establish a further synthetic index, constructed Applied Ergonomics September 1972
137
I Curve to left ~
Curve to right "-~'1 i
I S . , I ~,
0
I
b}
(c)
(d)
(~)
(f)
(g)
(h)
(i)
(j)
(k)
(t)
(o)
9
Fig 3 Possibilities for new steering elements (Coermann, 1968) (by courtesy of S. Karger, Basle - New York)
in tile following manner. For every preponderance of errors within a test pair of controls with no statistical significance, we charged one negative poin!; for those of P .05, two points, for P .01, four points, and for P .001, eight negative points. The sum of the 'penalty' points gives the virtues of the arrangement, and vice versa. To enable a general comparison of tile differences obtained between the control types tested, the averaged scores are combined in Table 2. However, since these scores are combined from different tests with diiTerent subjects, they can only be taken as a guide to the general differences between controls and not as a precise
Fig 4 Overall View of the testing device used at the Max-PlanckInstitute for Work-Physiology at Dortmund, Germany. A film projector, projecting the test'road' B the film loop of 7.5 m length C galvanometer giving the light spot for tracing the test 'road . . . . D the test-driver's seat, here with steering wheel arrangement E1 potentiometer feeding the deviations of the steering element into the registration system E2 compensating potentiometer assuring the zero level at the beginning of each run F digital voltmeter G tape drum delivering the tape for punching with instantaneous characteristics of the 'road' and of deviations fed in by the steering component 138
Applied Ergonomics September 1972
41
0
Fig 7 Arrangement with a steering wheel. Several modifications were tested, the steering angle and resistance being changed: 90 degrees from medium line to extreme left or right, and high resistance 90 degrees and medium resistance 180 degrees and medium resistance 180 degrees and low resistance 360 degrees (i e, one full turn to each side) and low resistance Other combinations were shown to be unrealistic
I;
Fig 5 Projecting screen with photo-elements reading the codes pertinent to each picture of the 'road' and feeding them into the tape
ISr
2"~
I
0
100
200
3?5
500
600
750
Fig 6 A part of the test 'road' showing the digital characteristics of the position of the dark spot, which in reality was the beam of the controlled galvanometer C in Fig 4. The task of the test subjects was to hold this beam and the light spot as precisely as possible upon the 'road' by moving it only from side to side, the horizontal level being fixed by the system at ]/3 distance up the display from the bottom. At the right, the BCD-code is marked on every picture, but is invisible to the test subjects; it is read by the photo-elements in Fig 5
Fig 8 Arrangements with compounded side-levers. The light spot moved towards the depressed lever; the other lever went up simultaneously, thus allowing operation by one hand only. Theoretically, 90 ~ of lever movement was possible, but in practice this was limited to 60 ~ because of the restriction on the arms by the seat rest and partly because of the inconvenience in bending forward too far.
Applied Ergonomics September 1972
139
: .J ".,
\,
Fig 10 Arrangement with compounded pedals pushed from body-near position (right leg - right margin of the screen) to body-far position (right leg - left margin), and vice-versa
Fig 9 Arrangement with one central joy-stick moved from side to side - concommitant with the direction of the light beam
measure. Therefore only the large differences shbuld be considered. For example, the highest number (147) shows that in not a single pair of experiments was the pedalling arrangement superior to the steering-wheel with medium movement of 180~ and medium resistance which, in general, was the best condition.
Table 1 Scores derived from all comparisons for each control pair tested Pair of controls tested * First Wheel, Wheel, Wheel, Wheel, Wheel, Wheel,
Control tested first
Second 90, high 180, medium 180, medium 360, low 90, medium 180, low
34 21 12 36 20 25
9 28 41 10 16 18
Wheel, 90, high Side lever, 60, high Wheel, 90, medium Side lever, 60, medium Wheel, 90, low Side lever, 60, low
25 9 20 2 30 1
27 56 22 60 8 66
Wheel, 180, medium Joystick-- high
Joystick-high Wheel, 180, medium
5 38
43 11
Wheel, 180, medium Compounded pedals-high
Compounded pedals-high Wheel, 180, medium
0 73
74 0
Side lever, Wheel, 90, Side lever, Wheel, 90, Side lever, Wheel, 90,
60, high high 60, medium medium 60, low low
Wheel, Wheel, Wheel, Wheel, Wheel, Wheel,
180, medium 90, high 360, low 180, medium 180, low 90, medium
Control tested second
Scores assigned according to the significance of the difference found between the given controls from each control pair test
Significance Not significant P = 0.05 P = 0.01 P = 0.001
Score 1 2 4 8
* Each case gives type of control, number of degrees of movement on either side of the 'straight ahead' position, and the level of resistance to movement 140
Applied Ergonomics September 1972
Table 2 Combined error scores for comparison of control types tested Control type *
Wheel, Wheel, Wheel, Wheel, Wheel,
Combined error score
180, medium 90, medium 180, low 90, high 360, low
17 31 41 49 77
Side levers, 60, medium Side levers, 60, high Joystick - high Sidelevers, 60, low Compounded pedals-high
80 81 81 96 147
* Each case gives type of control, number of degrees of movement on either side of the 'straight ahead' position, and the level of resistance to movement
The results did not completely meet expectations as it was supposed that the precision of tracking would be highest with the steering-wheel having 45 ~ turn to the right and 45 ~ to the left. Apparently, with an apparatus of some mechanical resistance, the proprioception in subjects without a special and probably prolonged training did not allow the response required to avoid overshooting the trace. With apparatus of more precision, the optimum might perhaps be shifted more to the steering with limited rotation, but Katz (1925) has already shown the necessity for the driver to 'feel' the road through the steering element. Everyday experience underlines the importance of this observation. Conclusion
The method adopted, an up-to-date modification of the classical approach of Graf (1931, 1932), certainly does not allow an uncritical transfer of the experimental results in detail to the practical conditions of heavy roadtraffic. Nevertheless, the losses upon roads and the loads imposed upon drivers are rising instead of being reduced, and only the sum of many improvements in the lay-out of roads, signals, cars and their single elements, not to forget better training of drivers, gives some chance for the future. If we are to offer some recommendations from our experiments, the first one would be the reduction of the turns upon the steering-wheel necessary for the change of dkection, but not to such a degree that the smallest movement of the steering-wheel - in the hands of an average driver - would result in a considerable deviation. On the other hand, during parking manoeuvres and going at low speed round the sharp corners of city streets, a large deviation of the road wheels should result from a relatively small displacement of the circumference of the steering-wheel in order to make these operations faster and easier, especially for female drivers. These two requirements can be fulfilled only by progressive steering with a differential ratio of steering input to steering effect. Such a system has been made and successfully tested by Grossbach (1967).
References
Coermann, R. 1967 World Congress for Automotive Medicine, May 7 13, Vienna. Gestaltung yon Kraftfahrzeugen nach ergonomischen Gesischtspunkten. Coermann, R. 1968 1st Int Seminar Biomechanics Zurich, 1967, 258263 (Karger, Basel/New York) Kinetische Probleme beim Fiahren von Kraftfahzeugen.
Dunne, J. 1965 Automotive Industries, Philadelphia, Pa., May 1, 6263.Ford's new steering system. Gibbs, C.B. 1954 Brit JPsycbo145, 24 - 39. The continuous regulation of skilled response by kinaesthetic feedback. Graf, O. 1931 Handbuch der biol. arbeitsmethoden, E. Abderhaden (ed.), Section IV, part 13, Urban & Schwarzenberg, Berlin - Munich - Vienna. Die Methodik des pharmakiologischen Arbeitsver suchs. Graf, O. 1932 Arbeitsphysiologie (Dortmund) 6, 169. ()ber den Zusammenhang zwischen Alkoholblutkonzentration und psychiescher Alkoholwirkung. Grime, G. 1968 Ergonomics 1.2, 151 - 162. Research on human factors in road transport. Grossbach, A. 1967 Private demonstration, patent pending. Hindle, T., Edwards, E., and Kirk, N.S. 1964 Design 189, 61 - 65. Motor car design and driving skill. Katz, D. 1925 Zschr. Psychol. (Barth), Leipzig, 270. Der Aufbau der Tastwelt, Erg~nzungsband 11. Kirk, N.S., Edwards, E., and Hindle, T. 1964 Design 188, 36 - 41. Designing the driver's workplace. Kroemer, K.H.E. 1966 Automobiltechnische Zeitschr 68.11,380 - 385. UngenU~ende Berncksichtigung arbeitsphysiologischer Erkenntnisse bei der Konstruction yon Kraftfahrzeugen als Unfallursach. Schreiber, A. 1914 Der Motorwagen, p 4. Ober linksseitige Steurung. Quoted by W. Lutter: Rechts oder links im Strabenverkehr, Res. Dept. Ministry of Traffic, Bonn, Germany, 1963, p 161. Shackel, B., Wilkes, E.G.M., and Blake, J.E. 1958 Design I 15, July, 29 - 35. Ergonomics versus styling in cars. Wcisz, A.Z., Allen, R.W., and Goddard, C.J. 1966 2nd Annual NASA-University Conference on Manual Control; MIT Cambridge (Mass.), NASA SP- 128. An evaluation of three types of hand controllers under random vertical vibration. Ziegler, P.N., and Chernikoff, R. 1967 Nav Res Lab Report 6646, 9 pp. A comparison of three types of manual controls on a third-order tracking task. Applied Ergonomics September 1972
141