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Driver's eye position relative to the ‘H’ point for trucks and buses
ApphedErgonomtcs, 4.3, 139-143
Driver's eye position relative to the "H" point for trucks and buses H.P. Ruffell Smith The eye position of subjects has been measured while they were driving the prototype of a bus intended for public service and in a static mock-up of this prototype. The average eye position observed in these tests was confirmed by photographing professional drivers while they drove an existing public servme bus. With seat backs inclined at 10 °, the average eye position was found to be between 1 0 and 11 cms (4 and 4.5 in) in advance of the hip hinge point. The eye position found in this way agrees with an SAE recommendation but differs in its fore and aft dimension relative to the hip joint from that specified m some national and international regulations. During a practical investigation, undertaken to check whether the chmensions of the driver's cab for a new single decker one man operated bus were satisfactory, subjects having body and limb dimensions representative of the population expected to act as drivers for this type of vehicle sat in the mock-up of the cab and the for and aft positron of their eyes was noted. Further trials were made of the same subjects whilst driving a prototype vehicle made to the same design. These trials were followed by a further confirmatory experiment In whlch experienced dnvers were observed wlulst driving a London Transport single decker one man operated bus.
Mock up experiment -- static measurements Method All the subjects were measured with respect to their overall height, sitting height, leg length from rear of buttocks with the hmb at right angles to the body and lower leg length from sole of foot to top knee with knee joint at a right angle. Ten subjects were selected with hmb and body measurements within the 45th to the 95th male and the 40th to 95th female percentiles. They were asked to position themselves in the mock up as though they were driving. All chose a seat back angle of 10°. Photographs were taken wRh the camera at a standard position about 3m (10ft) from the subjects and centred at the level of the seat pan In its mid posmon. The photographs, examples of which are shown In Figs 1 and 2, were traced to show the estimated body and thigh angles, the eye position and the H point. (Hip hinge point.) (SAE Standard J826.) Results The results are shown In Table 1 Although there may be parallax errors of some 6% m the measurements, the data suggest that in heavy vehcile drwers the average eye position should, for design purposes, be assumed to be some 10 cm ( 4 in) ahead of the H point. However, this surmise is known to be at variance with the
Based on Report LR440 of the Transport and Road Research Laboratory, Department of the Enwronment.
Table 1 Eye position Males (Four professional commercml vehicle drivers and one non-professional but w~th heavy commerc=al veh=cle experience)
Subject
Eye position ahead of the H point
Nearest cm
inches
15 8 9 10 10
6-0 3-0 3-5 4.0 4.0
1 2 3 4 5 Average 10-4 cm (4.1 sn)
Females (Non-drivers except subject 1) 1 2 3 4 5 Average 6-4 cm (2.5 m)
11 9 6 3 3
4"5 3"5 2"3 10 1"0
eye position indicated in the regulatory requirements of several countries and m some pubhshed scientific papers, as is shown by a search of the literature and perusal of re~latlons and drawings of existing or projected bus cab layouts. The sources of this reformation with the horizontal &stances between eye posmon and H point ln&cated me gwen In Table 2.
First driving experiment Method In view of the difference between the eye position found by pramtcal trials m the mock up and those specified m some regulations, it was decided that the matter should be further investigated. With the help of British Leyland Motors, arrangements were nlade to photograph six ot the same sublects, having sl7es within the percentiles for which
Applied Ergonom=cs September 1973
139
Table 2 Fore and aft eye position for commercial vehicles Regulations Austria Denmark West Germany
Apparently over the H point Apparently over the H point Apparently over the H point
Recommendations Federated Motor Vehmle Safety Standards (US) European Economm Community. Motor Vehicle Regulatmns 11 3.1
Over the H point Over the H point
Reports Driver's space design for standard one man operated bus. Dupu~s, H., and Hartnlng, E. (Max Plank Inst, Bad Kreuznach) ATZ 70(1968)11 SAE Tech Report J 941b (1969)
Human Data for Boeing Computerized Man Model. Ryan, P.W., and Stringer, W.E. US Navy ONR Project No NR 213.065 Space Requtrements of the seated Operator. Dempster, W.T. Wright Atr Development Centre Report 55/159 Two Dimensional Mannikin for use m the Design of Naval eqmpment. Wh0tney, R.J., Lee, D.E., and Pearse, R. Royal Naval Personnel Research Committee, Operational Subcommittee report No 382 (Supplement to RNP 60/912) The Measure of Man (2nd Edition 1968). Dreyfuss, H. Published by Whitney. Library of Design, New York
Not stated, but from the drawings over the H point
Passenger cars -- over the H point.Trucks and Buses* - over the H point for 20 ° seat back angle, 4in in front of H point for 11 ° seat back angle. (*Appendix based on opimon only) 10-2 cm (4m) ahead of the H point
10"2 cm (4m) ahead of the H point 10-2 cm (4m) ahead of the H point
Over the H point
Drawings Leyland FPB7 Bus Sept 1969 VOV Bus Drivers Compartment Layout 1.7.68 Manchester Bus Drawing of cab layout driver's position on drawing I D 295.02.4.8.69 LTE Drawing of cab layout driver's position on AEC Merhn ChassmsDrawing No SK 3819E 21.5.69 Bristol Bus Drawing Cab Compartment 30.10.69 Drawing DRR 555 Duplex Coach Builders on Bedford YR8 Chassis
the vehicle was designed, while driving the prototype bus to which the mock-up referred. Although exactly comparable condmons for the photographs were impossible, because the camera had to be located m the bus, faMy close snmlarlty was achieved. The subjects were each photographed twice without knowing when they were being photographed, the same two posmons on the track being used on all accaslons, one on a right hand curve. Examples of the photographs are shown in Figs 3 and 4. All the tests were undertaken on the same day with slmdar road and hght concht]ons. Tracings were made from the photographs of the subjects to show the estimated body and thigh angles and the eye positions relative to thetr estimated H point. Results The results are shown m Table 3. These ~esults agree closely with those arrived at in the mock-up, and the average fore and aft eye position indicated 140
Applied Ergonomics September 1973
Over the H point 5.1 cm (2in) ahead of the H point Over the H point Over the H point Over the H point 5-1 cm (2m) ahead of the H point
Table 3 Fore and aft dimensions of eye posit=on relative to subjects H point mn heavy commercial vehicles (Seat back angle 10°) Subjects
Distance of eye position =n front of the H point Driving straight ahead Nearest cm inches
Driving round curve Nearest cm inches
Female 1
13
5-2
10
4-0
Males 1 2 3 4 5
10 8 10 14 15
4-0 3-0 4.0 5-6 5.7
10 10 11 10 6
4.0 4-0 4.2 4-0 24
Male average
11
4 5
9
37
Overallaverage 12
4-6
10
3-8
F=g 1. Subject ,n mock-up of bus cab
FDg 3. Subject in prototype bus, going straLght ahead
Fig 2. Female subject ,n bus cab mock-up
F=g 4. Male subject drlwng straight ahead m prototype bus Apphed Ergonomics September 1973
141
of 15 bus driving instructors who vaned m height from 160.7 cm (63-3in) to 187-3 cm (73-3in) and for photographing them whilst driving an LTE one man operated single decker bus on the internal roads at the Chlswlck Works. The subjects were told collectwely that the object of the experiment was to relate new bus driving compartments to the posture of experienced drivers. They were mdwldually measured for total sitting height (other measurements were made at the same time but they are not relevant to tins particular study). The next day each driver adjusted the seat of the bus to their preferred fore and aft and vertical position. At tins Ume the observer placed an adheswe &sc on the side of their trousers over their H point as assessed by palpatmn during flexaon and extensmn of the Inp. The drivers then drove two clrcmts of the same route (approxamately 1.6 km (1 mde)). Dunng the second circmt, four photographs were taken from a positaon at right angles to the drwer's seat, two winle driving straight ahead and two while negotmtmg a right hand bend. An example is shown at Fig 5. Tracings were made from the photographs of the subjects to show the esttrnated body and thagh angles and the eye posmons relatwe to their estimated H point. Results The results are shown m Table 4. It is reahsed that these measurements include a parallax error due to the &fferent lateral positions of the eye. H point and reference scale, m this case about 10% rather than 6% because of smaller camera distance than was used m the static mock-up. However, this wdl st~ll be too small to effect the results slgmficantly.
Fig 5. Subject in LTE bus, going straight ahead by both sets of results is similar to that recommended by the SAE m the appen&x to their report J941 (b). However, it seemed desirable to support the finchng with trials of a larger number of subjects.
Second driving experiment Method Through the good offices of the London Transport Executwe, faclhtles were made avadable for the measurement
The vahdlty of the method used has been checked by companng the vertical &stances of the subject's eye position from the H point obtained from the photographs allowing for 10% parallax errors and those of their erect anthropological sitting heights that were measured directly
Table 4: Relationship of eye position to H point of 16 subjects driving an LTE one man operated bus; both whilst going straight and in a turn (inches)
Subject
Height overall Nearest cm inches
A B C D E F G H I J K L M N 0 Average
142
Straight Photo 1 Nearest cm inches
Eye position ahead of H point Straight Turning Photo 2 Nearest cm Inches
Photo 1 Nearest cm inches
Turning Photo 2 Nearest cm inches
179 173 170 184 179 171 169 161 187 175 184 164 187 179 177
70-3 68-3 68-5 72-3 70-3 67-3 66"5 63"3 73"8 68.8 725 64"5 73.5 703 69-5
13 14 10 17 8 6 8 8 5 13 11 13 20 8 18
5-0 5"5 4"0 6-5 3-0 2-5 3"0 3"0 20 5.0 4"3 50 8.0 30 7-0
11 13 11 17 14 6 9 5 3 15 11 12 19 8 15
4-5 5-0 4-3 6-5 5-5 2-5 3-5 20 1-0 6"0 4"5 4.8 75 3.0 6-0
15 14 11 20 13 10 12 4 5 20 14 13 20 10 15
6-0 5-5 4.5 8-0 5-0 4-0 4-8 1"5 2-0 8"0 55 5"0 80 4"0 6"0
15 13 9 19 9 12 8 7 6 19 17 13 19 11 15
6"0 5"0 3"5 7-5 3-5 4-8 3"0 2.8 2"5 7.5 65 50 7"5 45 60
175-8
69"2
11"5
4-5
11 5
45
13.2
52
12.7
50
Apphed Ergonomics September 1973
Table 5. Relation of the eye posit,on of subjects to the=r sitting height during drwmg
Eye pos,tion above SRP
Erect sitting height
(measured from photos corrected for parallax)
(measured directly from subjects)
Differences
Nearest cm
inches
Nearest cm
inches
Nearest cm
inches
75 75 75 75 72 75 73 73 79 73 72 71 73 73 70
29'7 29 7 29"4 29"4 28.3 29.7 28 6 28.6 31-1 28"8 28.5 28 0 28-6 28-8 27-7
92 92 90 94 91 92 87 86 94 91 92 88 97 92 93
36"3 36.3 35.5 37.0 36"0 36"5 34-3 34-0 37.0 36.0 36.3 34 8 38 3 36-3 36-8
17 17 16 19 20 17 15 14 15 18 20
6-6 66 6 1 7.6 7.7 6.8 57 5.4 5.9 72 7.8
17
68
25 19 23
9 7 Marked Slump 75 9 1 ....
73-6
29"0
91.4
36-0
18.0
7-1
Pred=cted from anthropological data 75-2
29-6
92" 1
36-3
17-0
6"7
A
B C D E F G H
I J K L M
N O Average
pnor to the experiment. Table 5 shows that ff an allowance of 5.1 cm (2m) Is made for slump, the average chfference between the eye to Seat Reference Point (SRP) distance and the erect sitting height for the subjects is 18 cm (7-hn) instead of the 17 cm (6-7m)that could be prechcted from anthropological data. Also, the measured average eye height of 73-7 cm (29-0m) agrees fairly well with the 75.2 cm (29-6m) reported by McFarland, Damon and Stoudt, (American Journal of Physical Anthropology 16.1.24,1958) and a similar figure corrected for a different reference datum was reported by Moore m RRL Report LN 1842.
Discussion and conclusion In view of the close correlatzon between the figures obtained m the mock up and during driving of the prototype by the same individuals as well as with those from another group of professmnal drivers whdst drwmg a different bus but w~th a simdar seat, it seems fatr to assume that, with a seat back angle of 10° to the vertical, the average eye posmon of bus drivers ~s honzontaUy
between 10 and 11 cms (4 and 4-5 m) ahead of their H points. This finding agrees with the recommendation m the Appendix to SAE Report J941 (b) 1969 Motor Vehicle Dnvers Eye Range and suggests that this eye position should be used to calculate the view out of these vehicles rather than one posmoned directly over the H point as m the European Economic Commumty proposal Motor Vehicle Regulataons 11.3.1, (Field of Vmon, Viewpoint). The results of tlus experiment reiterate the need to check actual body posmons m work places that have been arrived at by the use of manmkans with those of hve subjects performing the task m hand.
Acknowledgements This Report was prepared m the Vehicles Secuon of the Safety Dlvmon. The Laboratory is indebted to the London Transport Executive and to Bnt~sh Leyland Motors for the provmon of facflmes and to the subjects for their helpful co-operation.
Applied Ergonomics September 1973
143
Driver's eye position relative to the "H" point for trucks and buses H.P. Ruffell Smith The eye position of subjects has been measured while they were driving the prototype of a bus intended for public service and in a static mock-up of this prototype. The average eye position observed in these tests was confirmed by photographing professional drivers while they drove an existing public servme bus. With seat backs inclined at 10 °, the average eye position was found to be between 1 0 and 11 cms (4 and 4.5 in) in advance of the hip hinge point. The eye position found in this way agrees with an SAE recommendation but differs in its fore and aft dimension relative to the hip joint from that specified m some national and international regulations. During a practical investigation, undertaken to check whether the chmensions of the driver's cab for a new single decker one man operated bus were satisfactory, subjects having body and limb dimensions representative of the population expected to act as drivers for this type of vehicle sat in the mock-up of the cab and the for and aft positron of their eyes was noted. Further trials were made of the same subjects whilst driving a prototype vehicle made to the same design. These trials were followed by a further confirmatory experiment In whlch experienced dnvers were observed wlulst driving a London Transport single decker one man operated bus.
Mock up experiment -- static measurements Method All the subjects were measured with respect to their overall height, sitting height, leg length from rear of buttocks with the hmb at right angles to the body and lower leg length from sole of foot to top knee with knee joint at a right angle. Ten subjects were selected with hmb and body measurements within the 45th to the 95th male and the 40th to 95th female percentiles. They were asked to position themselves in the mock up as though they were driving. All chose a seat back angle of 10°. Photographs were taken wRh the camera at a standard position about 3m (10ft) from the subjects and centred at the level of the seat pan In its mid posmon. The photographs, examples of which are shown In Figs 1 and 2, were traced to show the estimated body and thigh angles, the eye position and the H point. (Hip hinge point.) (SAE Standard J826.) Results The results are shown In Table 1 Although there may be parallax errors of some 6% m the measurements, the data suggest that in heavy vehcile drwers the average eye position should, for design purposes, be assumed to be some 10 cm ( 4 in) ahead of the H point. However, this surmise is known to be at variance with the
Based on Report LR440 of the Transport and Road Research Laboratory, Department of the Enwronment.
Table 1 Eye position Males (Four professional commercml vehicle drivers and one non-professional but w~th heavy commerc=al veh=cle experience)
Subject
Eye position ahead of the H point
Nearest cm
inches
15 8 9 10 10
6-0 3-0 3-5 4.0 4.0
1 2 3 4 5 Average 10-4 cm (4.1 sn)
Females (Non-drivers except subject 1) 1 2 3 4 5 Average 6-4 cm (2.5 m)
11 9 6 3 3
4"5 3"5 2"3 10 1"0
eye position indicated in the regulatory requirements of several countries and m some pubhshed scientific papers, as is shown by a search of the literature and perusal of re~latlons and drawings of existing or projected bus cab layouts. The sources of this reformation with the horizontal &stances between eye posmon and H point ln&cated me gwen In Table 2.
First driving experiment Method In view of the difference between the eye position found by pramtcal trials m the mock up and those specified m some regulations, it was decided that the matter should be further investigated. With the help of British Leyland Motors, arrangements were nlade to photograph six ot the same sublects, having sl7es within the percentiles for which
Applied Ergonom=cs September 1973
139
Table 2 Fore and aft eye position for commercial vehicles Regulations Austria Denmark West Germany
Apparently over the H point Apparently over the H point Apparently over the H point
Recommendations Federated Motor Vehmle Safety Standards (US) European Economm Community. Motor Vehicle Regulatmns 11 3.1
Over the H point Over the H point
Reports Driver's space design for standard one man operated bus. Dupu~s, H., and Hartnlng, E. (Max Plank Inst, Bad Kreuznach) ATZ 70(1968)11 SAE Tech Report J 941b (1969)
Human Data for Boeing Computerized Man Model. Ryan, P.W., and Stringer, W.E. US Navy ONR Project No NR 213.065 Space Requtrements of the seated Operator. Dempster, W.T. Wright Atr Development Centre Report 55/159 Two Dimensional Mannikin for use m the Design of Naval eqmpment. Wh0tney, R.J., Lee, D.E., and Pearse, R. Royal Naval Personnel Research Committee, Operational Subcommittee report No 382 (Supplement to RNP 60/912) The Measure of Man (2nd Edition 1968). Dreyfuss, H. Published by Whitney. Library of Design, New York
Not stated, but from the drawings over the H point
Passenger cars -- over the H point.Trucks and Buses* - over the H point for 20 ° seat back angle, 4in in front of H point for 11 ° seat back angle. (*Appendix based on opimon only) 10-2 cm (4m) ahead of the H point
10"2 cm (4m) ahead of the H point 10-2 cm (4m) ahead of the H point
Over the H point
Drawings Leyland FPB7 Bus Sept 1969 VOV Bus Drivers Compartment Layout 1.7.68 Manchester Bus Drawing of cab layout driver's position on drawing I D 295.02.4.8.69 LTE Drawing of cab layout driver's position on AEC Merhn ChassmsDrawing No SK 3819E 21.5.69 Bristol Bus Drawing Cab Compartment 30.10.69 Drawing DRR 555 Duplex Coach Builders on Bedford YR8 Chassis
the vehicle was designed, while driving the prototype bus to which the mock-up referred. Although exactly comparable condmons for the photographs were impossible, because the camera had to be located m the bus, faMy close snmlarlty was achieved. The subjects were each photographed twice without knowing when they were being photographed, the same two posmons on the track being used on all accaslons, one on a right hand curve. Examples of the photographs are shown in Figs 3 and 4. All the tests were undertaken on the same day with slmdar road and hght concht]ons. Tracings were made from the photographs of the subjects to show the estimated body and thigh angles and the eye positions relative to thetr estimated H point. Results The results are shown m Table 3. These ~esults agree closely with those arrived at in the mock-up, and the average fore and aft eye position indicated 140
Applied Ergonomics September 1973
Over the H point 5.1 cm (2in) ahead of the H point Over the H point Over the H point Over the H point 5-1 cm (2m) ahead of the H point
Table 3 Fore and aft dimensions of eye posit=on relative to subjects H point mn heavy commercial vehicles (Seat back angle 10°) Subjects
Distance of eye position =n front of the H point Driving straight ahead Nearest cm inches
Driving round curve Nearest cm inches
Female 1
13
5-2
10
4-0
Males 1 2 3 4 5
10 8 10 14 15
4-0 3-0 4.0 5-6 5.7
10 10 11 10 6
4.0 4-0 4.2 4-0 24
Male average
11
4 5
9
37
Overallaverage 12
4-6
10
3-8
F=g 1. Subject ,n mock-up of bus cab
FDg 3. Subject in prototype bus, going straLght ahead
Fig 2. Female subject ,n bus cab mock-up
F=g 4. Male subject drlwng straight ahead m prototype bus Apphed Ergonomics September 1973
141
of 15 bus driving instructors who vaned m height from 160.7 cm (63-3in) to 187-3 cm (73-3in) and for photographing them whilst driving an LTE one man operated single decker bus on the internal roads at the Chlswlck Works. The subjects were told collectwely that the object of the experiment was to relate new bus driving compartments to the posture of experienced drivers. They were mdwldually measured for total sitting height (other measurements were made at the same time but they are not relevant to tins particular study). The next day each driver adjusted the seat of the bus to their preferred fore and aft and vertical position. At tins Ume the observer placed an adheswe &sc on the side of their trousers over their H point as assessed by palpatmn during flexaon and extensmn of the Inp. The drivers then drove two clrcmts of the same route (approxamately 1.6 km (1 mde)). Dunng the second circmt, four photographs were taken from a positaon at right angles to the drwer's seat, two winle driving straight ahead and two while negotmtmg a right hand bend. An example is shown at Fig 5. Tracings were made from the photographs of the subjects to show the esttrnated body and thagh angles and the eye posmons relatwe to their estimated H point. Results The results are shown m Table 4. It is reahsed that these measurements include a parallax error due to the &fferent lateral positions of the eye. H point and reference scale, m this case about 10% rather than 6% because of smaller camera distance than was used m the static mock-up. However, this wdl st~ll be too small to effect the results slgmficantly.
Fig 5. Subject in LTE bus, going straight ahead by both sets of results is similar to that recommended by the SAE m the appen&x to their report J941 (b). However, it seemed desirable to support the finchng with trials of a larger number of subjects.
Second driving experiment Method Through the good offices of the London Transport Executwe, faclhtles were made avadable for the measurement
The vahdlty of the method used has been checked by companng the vertical &stances of the subject's eye position from the H point obtained from the photographs allowing for 10% parallax errors and those of their erect anthropological sitting heights that were measured directly
Table 4: Relationship of eye position to H point of 16 subjects driving an LTE one man operated bus; both whilst going straight and in a turn (inches)
Subject
Height overall Nearest cm inches
A B C D E F G H I J K L M N 0 Average
142
Straight Photo 1 Nearest cm inches
Eye position ahead of H point Straight Turning Photo 2 Nearest cm Inches
Photo 1 Nearest cm inches
Turning Photo 2 Nearest cm inches
179 173 170 184 179 171 169 161 187 175 184 164 187 179 177
70-3 68-3 68-5 72-3 70-3 67-3 66"5 63"3 73"8 68.8 725 64"5 73.5 703 69-5
13 14 10 17 8 6 8 8 5 13 11 13 20 8 18
5-0 5"5 4"0 6-5 3-0 2-5 3"0 3"0 20 5.0 4"3 50 8.0 30 7-0
11 13 11 17 14 6 9 5 3 15 11 12 19 8 15
4-5 5-0 4-3 6-5 5-5 2-5 3-5 20 1-0 6"0 4"5 4.8 75 3.0 6-0
15 14 11 20 13 10 12 4 5 20 14 13 20 10 15
6-0 5-5 4.5 8-0 5-0 4-0 4-8 1"5 2-0 8"0 55 5"0 80 4"0 6"0
15 13 9 19 9 12 8 7 6 19 17 13 19 11 15
6"0 5"0 3"5 7-5 3-5 4-8 3"0 2.8 2"5 7.5 65 50 7"5 45 60
175-8
69"2
11"5
4-5
11 5
45
13.2
52
12.7
50
Apphed Ergonomics September 1973
Table 5. Relation of the eye posit,on of subjects to the=r sitting height during drwmg
Eye pos,tion above SRP
Erect sitting height
(measured from photos corrected for parallax)
(measured directly from subjects)
Differences
Nearest cm
inches
Nearest cm
inches
Nearest cm
inches
75 75 75 75 72 75 73 73 79 73 72 71 73 73 70
29'7 29 7 29"4 29"4 28.3 29.7 28 6 28.6 31-1 28"8 28.5 28 0 28-6 28-8 27-7
92 92 90 94 91 92 87 86 94 91 92 88 97 92 93
36"3 36.3 35.5 37.0 36"0 36"5 34-3 34-0 37.0 36.0 36.3 34 8 38 3 36-3 36-8
17 17 16 19 20 17 15 14 15 18 20
6-6 66 6 1 7.6 7.7 6.8 57 5.4 5.9 72 7.8
17
68
25 19 23
9 7 Marked Slump 75 9 1 ....
73-6
29"0
91.4
36-0
18.0
7-1
Pred=cted from anthropological data 75-2
29-6
92" 1
36-3
17-0
6"7
A
B C D E F G H
I J K L M
N O Average
pnor to the experiment. Table 5 shows that ff an allowance of 5.1 cm (2m) Is made for slump, the average chfference between the eye to Seat Reference Point (SRP) distance and the erect sitting height for the subjects is 18 cm (7-hn) instead of the 17 cm (6-7m)that could be prechcted from anthropological data. Also, the measured average eye height of 73-7 cm (29-0m) agrees fairly well with the 75.2 cm (29-6m) reported by McFarland, Damon and Stoudt, (American Journal of Physical Anthropology 16.1.24,1958) and a similar figure corrected for a different reference datum was reported by Moore m RRL Report LN 1842.
Discussion and conclusion In view of the close correlatzon between the figures obtained m the mock up and during driving of the prototype by the same individuals as well as with those from another group of professmnal drivers whdst drwmg a different bus but w~th a simdar seat, it seems fatr to assume that, with a seat back angle of 10° to the vertical, the average eye posmon of bus drivers ~s honzontaUy
between 10 and 11 cms (4 and 4-5 m) ahead of their H points. This finding agrees with the recommendation m the Appendix to SAE Report J941 (b) 1969 Motor Vehicle Dnvers Eye Range and suggests that this eye position should be used to calculate the view out of these vehicles rather than one posmoned directly over the H point as m the European Economic Commumty proposal Motor Vehicle Regulataons 11.3.1, (Field of Vmon, Viewpoint). The results of tlus experiment reiterate the need to check actual body posmons m work places that have been arrived at by the use of manmkans with those of hve subjects performing the task m hand.
Acknowledgements This Report was prepared m the Vehicles Secuon of the Safety Dlvmon. The Laboratory is indebted to the London Transport Executive and to Bnt~sh Leyland Motors for the provmon of facflmes and to the subjects for their helpful co-operation.
Applied Ergonomics September 1973
143