STUDIES OF HUMAN FACTOR IN PANEL DESIGN 



155 



The Use of Anthropometric Data. A sec- 

 ond, and perhaps more valuable, method of 

 determining the hmits of reach is to make 

 use of the data on body size collected in 

 anthropological studies. If the arm length, 

 leg length, and standing and sitting heights 

 of the men who are likely to use a particular 

 piece of equipment are known, it is quite pos- 

 sible to calculate what distances they will be 

 able to reach on horizontal and vertical 

 surfaces. In one study in the Army Air 

 Forces, such measurements were made on 

 about 3000 cadets (Table I), and the distri- 

 butions of data were presented in such a way 

 that it was possible to tell what distances 

 would be bej^ond the reach of 5%, 50%, and 

 95% of the population if the body were held 

 in a fixed position (31). In a similar kind 

 of investigation, in the Navy, even more di- 

 rect data on the limits of reach in the cockpit 

 were obtained (21). In this case, only 139 

 subjects were used, but the distributions of 

 measurements obtained agreed fairly well 

 with those of the larger cadet sample. All 

 measurements were made with the subjects 

 seated properly in a standard pilot's chair 

 and extending their right arms to reach 

 horizontal and vertical measuring rods which 

 gave coordinates from a reference point on 

 the seat (Fig. 3). Analysis of the data 

 showed the maximal horizontal and vertical 

 distances that could be reached by 97% of 

 the population when the body was fixed 

 against the chair back and the chair tilted 

 13° backwards (Figs. 3 and 4). In both of 

 these studies, again, the estimates of the 

 working area are conservative, for all meas- 

 urements were made with the subjects' 

 heads and bodies in fixed positions. Even 

 though it is considered desirable to keep 

 gross trunk movements and stretching at a 

 minimum, it would be important to know 

 how far an operator could reach, if he had 

 to, and still operate his equipment. 



Both of these techniques were applied in a 

 recent study of the limits of reach on a verti- 

 cal surface (24). Eight subjects were seated 

 at viewing distances of 10, 15, and 20 inches 



from a wall chart on which they traced the 

 movements of their outstretched hands while 

 their heads and bodies were fixed against a 

 chair back. By comparing the body sizes of 

 these subjects to the population of aviation 

 cadets, the hmits of reach of 5%, 50% and 



Fig. 2. Normal and maximum working space in 

 three dimensions. (From Barnes, 2) 



TABLE I 



Some Body Size Measurements of about 2960 



Aviation Cadets, Showing the 5th, 50th, 



AND 95th Percentiles (in Inches) of 



THE Distributions 



(From Randall et al., 31) 



Measurement 



Standing Height 



Sitting Height 



Anterior Arm Reach, 

 Buttock to Knee. . . . 

 Patella to Knee 



Percentiles 



5th SOth 9Sth 



65.4 

 34.5 

 32.7 

 22.0 

 20.4 



69.2 

 36.5 

 35.2 

 23.6 

 22.0 



73.1 

 38.5 

 37.8 

 25.6 

 23.6 



95% of that population could be calculated. 

 Fig. 5 shows a sample of the detailed infor- 

 mation that this type of study yields. The 

 two hands traced overlapping circles that 

 varied in size as a function of the physical 

 size of the operator and the distance he sat 

 from the vertical surface. For example, it 

 was shown that to include 95% of the popu- 

 lation, at a viewing distance of 20 inches, the 



