Safe Workplace for Agricultural Tractor: Design Principle and Application

Abstract

This study focuses on developing a safe workplace for agricultural tractor drivers and recommending the optimum location for tractor control. Thirteen anthropometric body dimensions of 8,025 Indian male agricultural workers were considered for developing reach envelopes for hand- and foot-operated controls. The optimum reach for hand controls is in the range of 456 to 700 mm forward and 265 to 492 mm above the seat reference point. Similarly, for foot-operated control, the foot could reach within the range 429 to 897 mm forward and 367 mm below, and 30 mm above the seat reference point.

Keywords

workplace agricultural seat reference point reach envelopes controls anthropometric

Why there is a need for Safe Workplace on Agricultural Tractor?

Ergonomics and safety aspects in the design of the tractor workplace have received much attention particularly with respect to vibration, noise, and operator seating space. Human factors, namely, driving, comfort, safety, visibility, and location of controls were considered for designing a comfortable workplace for the operators. Farm mechanization has increased the production and productivity of Indian farms. However, inadvertent use of agricultural machinery without proper attention to health and safety aspects has caused more injuries to agricultural workers through accidents. Agricultural tractors are considered to be the most accident-prone machinery followed by thresher and power tillers. The main causes of agricultural accidents are improper design of the operator’s workplace and tools/equipment, lack of knowledge/training, ignorance, tiredness, and so on. Therefore, if due attention is not given while designing the operator’s workplace, the fatality rate may increase causing a great loss to our society in general and to the agricultural workers in particular, especially the tractor drivers.

According to the report of All India Coordinated Research Project (AICRP) on Ergonomics and Safety in Agriculture (ESA, 2002), about 36% operators felt uncomfortable while operating the controls of tractors. This indicated that the operator’s comfort and safety during tractor operation were affected by the poor design of the tractor workplace and the location of controls. If the controls were not as per the anthropometry, the operator’s performance will reach its maximum limits or even exceed the limits of tolerance causing excessive stress, early fatigue, and a higher possibility of accidents to the operator (Duppis, 1959; Suutarinum, 1992).

Hansson et al. (1970) reported that proper design of the operator’s workplace should be done based on the operator’s comfort, safety, and convenience. The controls should be placed on a machine so that visibility at the driver’s position should be good without requiring any awkward posture. Matthews and Knight (1971) had given the guidelines for developing the reach envelopes and recommended the optimum pedal space for British operators. Zander (1972) carried out studies on combined harvester controls and suggested seat movements for comfortable operations of the tractor controls. Pheasant and Harris (1982) concluded that for better driving posture and optimum force application, the pedal location should be at 12.5% below the seat reference point (SRP) and 47.5% in front of the SRP. Hammer (1991) reported that about two thirds of the accidents occurred at the time of dismounting from the tractors by analyzing the body postures relative to alternative workplace designs. Patel et al. (2000) reported developing an ergonomic facility for the improvement of tractor design by using the workplace envelope of the Indian population.

A few studies on operator’s workplace for tractors or self-propelled machinery have been carried out in the country. These studies conceded on Indian tractor operator’s workplace layout and reported that most of the tractor control locations were on the higher side compared with that given in the BIS 12343 standard (BIS, 1998; Khadatkar et al., 2017; Kumar et al., 2009; Mehta et al., 2007; Tiwari, 2001; Yadav, 1995). This is because the BIS 12343 (1998) has adopted ISO 4253 (International Organization for Standardization, 1993) and ISO 15077 (International Organization for Standardization, 2008) standards, which are basically anthropometric data of the Western population.

Studies on tractor seat were also carried out that recommended the optimum seat dimensions for agricultural tractors, namely, seat height, seat pan width, seat backrest width bottom and top, seat pan tilt, and seat pan length for the operators (Mehta et al., 2008; Tewari & Prasad, 2000). In another study, Mehta et al. (2011) recommended that maximum actuating forces should be below 260 N and 125 N of right and left leg strength, respectively, for frequently operated clutch and brake pedals of tractor operations. Also, the maximum actuating force should be below 51 N of torque strength (both hands) for steering wheel operation during the sitting conditions. The required maximum actuating forces should be below 46, 46, 25, and 25 N gear selection, speed selection, hydraulic control, and hand throttle, respectively, for operating levers of Indian tractors.

Some studies suggested the use of anthropometric body dimensions of Indian agricultural workers for the design of improved tools/equipment (Gite et al., 2009; Gite & Yadav, 1989; Gupta et al., 1983; Mehta et al., 2018; Sen et al., 1977). If the locations of controls are not properly designed as per the anthropometric data of the reference population, the performance might be altered. As a result, it will cause poor work output, accidents will be increased, or the tractor operator may risk his life. Therefore, the objective of this article is to develop a safe workplace for tractor operators considering the anthropometric parameters of the Indian male population. The reach envelopes for hand- and foot-operated controls were developed based on the anthropometric dimensions of Indian male workers to provide guidelines for workplace layout of tractors and self-propelled machinery.

Development of Workplace Layout for Agricultural Tractors

Anthropometric data on Indian male agricultural workers from 12 states were collected and compiled by the AICRP on ESA located at the Indian Council of Agricultural Research (ICAR)–Central Institute of Agricultural Engineering (CIAE), Bhopal (Gite et al., 2009). For the design consideration of the agricultural tractors, 13 anthropometric body dimensions were identified and collected.

Sample Size and Subjects

The 13 anthropometric dimensions of Indian male agricultural workers were collected from totally different communities as well as tribal populations from 12 states of India (Table 1) by ad hoc research scheme located at cooperating centers of AICRP on ESA. The subjects were randomly selected from the healthy agricultural workers in the age-group of 18 to 65 years. The procedure to measure the identified anthropometric body dimension used for the design of the tractor workplace for operator’s safety and comfort are shown in Figure 1 (Gite et al., 2009).

Table 1.

Anthropometric Data Collection Under AICRP on ESA and Ad Hoc Schemes (Gite et al., 2009)

No.	State	Center	No. of Subjects Surveyed
1	Arunachal Pradesh	NERIST, Nirjuli	644
2	Gujarat	GAU, Junagarh	733
3	Jammu & Kashmir	CAU, Sopore	485
4	Madhya Pradesh	CIAE, Bhopal	825
5	Maharashtra	KKV, Dapoli	649
		MAU, Parbhani	600
6	Meghalaya	ICAR unit, Barapani	564
7	Mizoram	NERIST, Nirjuli	257
8	Orissa	OUAT, Bhubaneswar	681
9	Punjab	PAU, Ludhiana	490
10	Tamil Nadu	TNAU, Coimbatore	1,000
11	Uttar Pradesh	CAET, Etawah	150
12	West Bengal	IIT, Kharagpur	947
Total			8,025

Note. AICRP = All India Coordinated Research Project; ESA = Ergonomics and Safety in Agriculture; NERIST = North Eastern Regional Institute of Science and Technology; GAU = Gujarat Agriculture University; CAU = Central Agriculture University of Jammu; CIAE = Central Institute of Agricultural Engineering; KKV = Konkan Krishi Vidyapeeth; MAU = Maharashtra Agriculture University; ICAR = Indian Council of Agricultural Research; OUAT = Odisha University of Agriculture and Technology; PAU = Punjab Agriculture University; TNAU = Tamil Nadu Agricultural University; CAET = College of Agricultural Engineering and Technology; IIT = Indian Institute of Technology.

Figure 1.

Measurement of various anthropometric body dimensions: (a) weight, (b) stature, (c) elbow rest height, (d) sitting acromial height, (e) elbow grip length, (f) wall-to-acromion distance, (g) biacromial breadth, (h) sitting height, (i) knee height sitting, (j) popliteal height sitting, (k) shoulder grip length, (l) buttock popliteal length, (m) buttock knee length, and (n) foot length.

As the anthropometric dimension is positively correlated to stature, the sample size for the anthropometry survey of Indian male agricultural workers was estimated as per the equation given below (Roebuck et al., 1975).

N = {(K * S D)}^{2} / d,

(1)

S D = \sqrt{{(Range)}^{2} / 36},

(2)

where N = sample size, SD = estimated standard deviation of the data (Raghavarao, 1983), d = desired accuracy of the measurement (e.g., 3 mm), and K = value chosen for statistics of interest (i.e., 4.14 for 5th and 95th percentiles).

Because the stature of Indian workers varies from 1,450 to 1,830 mm with a variation of 380 mm, the SD for stature was calculated as 63.33 mm. Thus, substituting the values of K, SD, and d in Equation 1, we get the sample size as 7,637 (Gite et al., 2009). Therefore, the minimum sample size required for anthropometric data collection should be higher than 7,637. So we have anthropometric data of 8,025 Indian male agricultural workers as representative data.

Anthropometric Measurement

For measurement of anthropometric body dimensions, the equipment used was the Harpenden Anthropometer, Siber Hegner Anthropometer, or integrated composite anthropometer (ICA) developed by the Indian Institute of Technology, Kharagpur; sliding calipers; and measuring tape (Figure 2; Gite et al., 2009).

Figure 2.

Equipment used for measurement of anthropometric body dimensions (a) integrated composite anthropometer (ICA) and (b) Harpenden Anthropometer with a vernier caliper.

Before collecting anthropometric dimensions, the staff members of cooperating centers were given adequate training at the ICAR-CIAE, Bhopal, for accurate and precise procedure of measurement of anthropometric dimensions. The trained staff members collected the anthropometric data of the selected workers in each village. The workers were screened so that those in normal health with no serious unwellness or physical disability were selected. For measuring the body dimensions in standing posture, the workers were asked to stand on a base platform of the ICA with their feet closed and their body vertically erect, while the heels, buttocks, and shoulders touched the same vertical plane. The ICA was adjusted for the height of the subject. While measuring the body dimensions, care was taken to avoid any excessive compression of the underlying tissues. In this study, the collected data were used to determine the 5th and 95th percentile values, mean, and SD for every anthropometric dimension with the help of Microsoft Excel. The anthropometric body dimensions of agricultural workers considered for developing reach envelopes for hand- and foot-operated controls are given in Table 2.

Table 2.

Anthropometric Data of Indian Male Agricultural Workers Used for Recommending Optimum Tractor Workplace (N = 8,025; Gite et al., 2009)

No.	Body Dimension	M	SD	5th Percentile	95^th Percentile
1	Age, years	34.0	10.2	17.3	50.7
2	Weight, kg	54.7	8.7	40.4	68.9
3	Stature, mm	1,633	68	1,521	1,746
4	Wall-to-acromion distance, mm	102	18	72	131
5	Elbow grip length, mm	354	31	304	404
6	Shoulder grip length, mm	723	58	628	818
7	Elbow rest height, mm	214	32	162	266
8	Sitting acromial height, mm	568	47	492	645
9	Biacromial breadth, mm	330	44	258	402
10	Knee height sitting, mm	504	36	444	563
11	Popliteal height sitting, mm	417	31	367	468
12	Buttock popliteal length, mm	442	37	382	502
13	Buttock knee length, mm	536	36	476	596
14	Foot length, mm	245	15	220	269
15	Sitting height, mm	830	52	744	916

Reach Envelope for Hand and Foot Controls

The methodology given by Matthews and Knight (1971) was adopted in developing the optimum reach envelopes for hand- and foot-operated controls for the tractor workplace. The optimum area for hand and foot is most appropriate for the position of the controls both in neutral and if displaced in any direction. The four points, that is, near high, near low, far low, and far high, optimize the workspace for hand and foot controls. Pro-e wildfire 5.0 software was used for making the reach envelopes.

The elbow pivot is shown as the point having 95th percentile value of elbow rest height vertically above and half of the 95th percentile value of wall-to-acromion distance forward of the SRP. The shoulder pivot point is shown as the point having the 5th percentile values of sitting acromion height vertically above and wall-to-acromion distance forward of the SRP to make sure controls do not seem to be placed too high for most of the operators. The toe point was placed on the tip of foot length, and the heel point is outlined by the center line of calf circumference.

Results and Discussion

Optimum Reach Envelope for Hand Controls

The optimum hand reach envelope was developed based on the anthropometric data of Indian male agricultural workers (N = 8,025) for generating the desired location of tractor controls. The anthropometry data used for making reach envelopes for hand-operated controls are elbow grip length, wall-to-acromion distance, sitting acromial height, shoulder grip length, and elbow rest height. Figure 3 shows the reach envelope for the optimum area for operating hand control in the sagittal (XY) plane. The near low point was drawn at 404 mm from the elbow point by taking the elbow grip length of 95th percentile population to ensure that the controls are not placed too close for most of the operators. Similarly, the far high point was drawn at 628 mm from the shoulder point by taking the shoulder grip length of the 5th percentile population to ensure that the controls are not placed too far from most of the operators. Analyzing the developed reach envelope for hand-operated controls of selected agricultural workers showed that the operator’s hand could reach horizontally and vertically within the limits of 456 to 700 mm forward and 265 to 492 mm above the SRP, respectively. Therefore, 90% of operators could easily operate the controls, if hand-operated tractor controls were placed within resulted envelope range.

Figure 3.

Reach envelope for optimum hand control for Indian male agricultural workers in the sagittal plane (all dimension in mm).

Figure 4 shows the envelope of the 5th and 95th percentiles for hand reach for the Indian user population. For design consideration, the 5th percentile value of Indian agricultural workers should be used so that the hand-operated controls should not be placed beyond 628 mm forward and 492 mm above the SRP. Also, for comfortable operation, the controls should not be placed behind the SRP or it should be as close as possible to SRP in rearward position, that is, 50 mm behind the SRP. The controls placed on the upper portion should not be above the reach of the 5th percentile population that is, 1,048 mm. But considering the height of the tractor cabin, it should be kept as 1,016 mm or below. The height of the cabin for the tractor should be designed considering the 95th percentile value of sitting height. The height of the cabin for the tractor should not be less than 916 mm plus a head clearance of about 100 to 150 mm. This will be the limiting value for the height of the cabin design. Therefore, it is recommended that the height of the cabin should be around 1,016 to 1,066 mm.

Figure 4.

The 5th and 95th percentile hand reach envelope for Indian male agricultural workers in the sagittal plane (all dimension in mm).

Figure 5 represents the top view of the 5th and 95th percentiles reach envelope for hand-operated controls for Indian male agricultural workers in the transverse plane. The reach envelopes are drawn taking the 5th and 95th percentile values of the shoulder grip length. An arc was drawn taking the 5th and 95th percentile values from the shoulder point (72, 198 mm) on both sides. This indicates that the hand controls should not be placed beyond 613 mm forward and 685 mm on both sides of the SRP considering the 5th percentile value of the user population. For efficient operation of the controls, the controls placed on both sides should not be beyond the 5th percentile value of the user population, that is, 685 mm. This will be the limiting value in deciding the width of the cabin, and the width of the cabin should not exceed 685 mm on both sides from SRP, while the front and the back portion should not exceed the 95th percentile value of 791 and may be kept between 613 and 791 mm from the SRP with some adjustment, if necessary.

Figure 5.

The top view of the 5th and 95th percentile hand reach envelope for Indian male agricultural workers in the transverse plane (all dimension in mm).

Optimum Reach Envelopes Foot Controls

For an optimum range of foot-operated controls, the controls need to be placed within the operator’s workplace for safety and better comfortability. The anthropometric body dimensions used for making reach envelopes for foot-operated controls are knee height sitting, buttock popliteal length, popliteal height sitting, foot length, and buttock knee length. Figure 6 shows the reach envelope for an optimum area for foot-operated controls in the sagittal (XY) plane. The point’s far low heel (H1) and far low toe (T1) show that the foot can rest at the lowest positions of the toe and heel. Also, the foot can reach the far high heel (H4) and far high toe (T4) points, which are the farthest location from SRP. Line H1–T1 was drawn using 5th percentile value of foot length. It represents that the location of the controls that are foot operated should not be placed below the line of H1–T1. The points H1 and T1 are located at 429 mm and 649 mm, respectively, in front of SRP and below SRP at a vertical distance of 374 mm. Any foot-operated controls placed below the H1–T1 line would be tough to reach for the 5th percentile of the user population. Therefore, the foot-operated controls should be located above the line H1–T1, so that 95% of the population can easily operate the controls.

Figure 6.

The 5th percentile leg reach envelope of Indian male agricultural workers in the sagittal plane (all dimension in mm).

The points near low heel (H2) and near low toe (T2) show the closest boundaries wherever the foot will reach while not having excessive bending of the leg at the knee joint. The far high heel (H4) and far high toe (T4) points are located at a horizontal distance of 787 mm and 897 mm, respectively in front of SRP. The vertical distance of T4 is 30 mm above the SRP. Especially, the controls operated by heel became difficult for the 5th percentile user operators when the control pedal was located at a horizontal distance greater than 787 mm. Therefore, the foot controls operated by heel should be placed between 429 and 787 mm forward and between 145 and 367 mm downward from SRP. And controls operated by toe should be placed 649 to 897 mm forward and 367 mm downward and 30 mm above the SRP.

The points H4 and T4 represent the farthest location of the foot-operated controls in their engaged position. For the 5th percentile user operators, it would be very difficult to reach to operate any foot controls located beyond this point. Also, the necessary force will not be exerted unless there is sufficient support from the seat backrest even if the operator stretches his legs and reaches for the operation of the foot pedals. Therefore, the foot controls should be easily operated by the 95th percentile user population, if foot controls were located within this envelope. Also, in this envelope H2–T2 and H3–T3 points represented the nearest boundaries of the reach envelope. The 5th percentile user population have to face difficulties if foot-operated controls are located above the H3–T3 point because the operators would have to lean their leg at the knee joint.

The control location difficult to reach for the 5th percentile user population would be suitable for a 95th percentile. Similarly, for the 5th percentile user operator, if the controls were placed too close to the H1–T1 points of leg reach envelope, then that would not be suitable for the 95th percentile user population. However, this issue can be reduced to a great extent by making longitudinal as well as vertical adjustments in the seat.

Based on the finding, the hand-operated controls should be placed within the limits of 456 to 700 mm forward and 265 to 492 mm above the SRP, respectively. Also, the foot-operated control that is, the heel may be located within the region of 429 to 787 mm forward and 367 mm below the SRP. Whereas the toe-operated controls may be located 897 mm forward and 30 mm above the SRP, and 649 mm forward and 367 mm below the SRP. Also, some design considerations should be taken care of while making a tractor cabin. The height recommended should be between 1,016 and 1,066 mm and the width of the cabin should not exceed 685 mm on both sides from SRP, while the front and back portions should not exceed the 95th percentile value of 791 and may be kept between 613 and 791 mm from the SRP with some adjustment if necessary.

The anthropometric body dimensions should be used in the design of tractor seat, seat height, seat pan width, seat backrest width bottom and top, seat pan tilt, and seat pan length for safety and comfort of the operators as recommended by various researchers (Hansson et al., 1970; Khadatkar et al., 2017; Mehta et al., 2008, 2011; Pheasant & Harris, 1982; Zander, 1972). Also, the strength data of the user population should be encouraged in recommending the optimum actuating force required in applying various operating levers, namely, gear selection, speed selection, hydraulic control, hand throttle, clutch and brake pedals, and so on. Future studies in accordance with this may also be carried out to develop a safe workplace using anthropometric and strength data on various accident-prone machinery, namely, combine harvester, power threshers, cane crushers, power tillers, heavy dozers, other forest machinery, and so on. Because the anthropometric body dimensions vary from region to region, it would be better to adapt region-specific data in the workplace design for better safety and comfort. However, it would not be possible in a commercial perspective; so some adjustment, namely, seat adjustment both in lateral and in longitudinal direction should be provided so that the operators can adjust their location as per their requirement.

Conclusion

The study highlights the need for anthropometric body dimensions of the user population in the design of various tractor controls and workplace for operator’s safety and comfort, which ultimately reduce the operator’s fatigue and chances of accidents. The frequently operated controls in tractors, such as steering wheel, clutch pedal, brake pedal, accelerator pedal, and so on, should be placed in optimum reach for hand- and foot-operated controls as shown in the reach envelopes. Therefore, it is concluded that agricultural tractors should be redesigned based on the area-specific user population for better safety and comfort of the operators, which ultimately reduces the risk of life and hence improves prosperity.

Footnotes

Acknowledgements

The authors are grateful to the Director, ICAR-CIAE, Bhopal, for the immense support and providing facilities. The authors also wish to thank the staff of the AICRP on Ergonomics and Safety in Agriculture, and all the participants who took part in the study.

Abhijit Khadatkar is a scientist in farm machinery and power currently working in ICAR-CIAE, Bhopal. He served for 9 years and carried out different research, extension, and training programs in ergonomics and safety in agriculture as well as in improved farm machinery. His significant contributions toward ergonomics were Makahan harvester; audiometric database and guidelines to reduce hearing impairment of agricultural tractor drivers; online database of anthropometric and strength parameters of agricultural workers; database on agricultural accident of Madhya Pradesh, India; design of control on Mahindra tractor based on ergonomical consideration; and demonstration model for transfer of technology for drudgery reduction of women leading to enhancement in livelihood. He has published more than 25 research papers in national and international journals; 25 popular articles, nine books/book chapters, seven leaflets, four bulletins/technical reports, one success story, and one patent. ORCID iD: .

Prabhakar Shukla is a research scholar in farm machinery and power currently pursing his PhD in ICAR-CIAE, Bhopal. He served as testing engineer for 3 years at SLFMTTI, Lucknow, and currently working on design of workplace on combine harvesters in Madhya Pradesh, India. He is working on workplace on combines under ergonomics and safety in agriculture. He has published seven research papers, two books/book chapters, five popular articles, and five bulletins/technical reports.

References

All India Coordinated Research Project on Ergonomics and Safety in Agriculture. (2002). Progress report and proceedings of second workshop of All India Coordinated Research Project on Human Engineering and Safety in Agriculture. Central Institute of Agricultural Engineering.

Bureau of Indian Standards. (1998). Agricultural tractors–operator’s seat–technical requirements (IS: 12343).

Duppis

(1959). Effects of tractor operation on human stresses. Agricultural Engineering, 40(3), 510–525. https://doi.org/10.2307/1929791

Gite

L. P.

Majumder

Mehta

C. R.

Khadatkar

(2009). Anthropometric and strength data of Indian agricultural workers for farm equipment design. Central Institute of Agricultural Engineering.

Gite

L. P.

Yadav

B. G.

(1989). Anthropometric survey for agricultural machinery design: An Indian case study. Applied Ergonomics, 20(3), 191–196. https://doi.org/10.1016/0003-6870(89)90076-8

Gupta

P. K.

Gupta

M. L.

Sharma

A. P.

(1983). Anthropometric survey of Indian farm workers. Agricultural Mechanisation in Asia, America and Latin America, 16(1), 27–30.

Hammer

(1991). Safe access to farm tractor and trailers. Agricultural Engineering Research, 50, 219–237. https://doi.org/10.1016/S0021-8634(05)80016-2

Hansson

J. E.

Sjoflot

Suggs

C. W.

(1970). Matching the farm machine to the operator’s capabilities and limitations. Implement & Tractor, 85, 10–13.

International Organization for Standardization. (1993). Agricultural tractors – operator’s seating accommodation–dimensions (ISO 4253).

10.

International Organization for Standardization. (2008). Tractors and self-propelled machinery for agriculture–operator controls–actuating forces, displacement, location and method of operation (ISO 15077).

11.

Khadatkar

Mehta

C. R.

Gite

L. P.

(2017). Development of reach envelopes for optimum location of tractor controls of central indian male agricultural workers. Agricultural Engineering Today, 41(2), 34–39.

12.

Kumar

Gaikwad

Singh

J. K.

(2009). Assessment of controls layout of Indian tractors. Applied Ergonomics, 40(1), 91–102. https://doi.org/10.1016/j.apergo.2008.01.017

13.

Matthews

Knight

A. A.

(1971). Ergonomics in agricultural equipment design. National Institute of Agricultural Engineering.

14.

Mehta

C. R.

Gite

L. P.

Khadatkar

(2018). Women empowerment through agricultural mechanization in India. Current Science, 114(9), 1934–1940. https://doi.org/10.18520/cs/v114/i09/1934-1940

15.

Mehta

C. R.

Gite

L. P.

Pharade

S. C.

Majumder

Pandey

M. M.

(2008). Review of anthropometric considerations for tractor seat design. International Journal of Industrial Ergonomics, 38(5–6), 546–554. https://doi.org/10.1016/j.ergon.2007.08.019

16.

Mehta

C. R.

Pandey

M. M.

Tiwari

P. S.

(2007). Development of tractor operator’s workplace layout based on ergonomical considerations (Technical Report III). Central Institute of Agricultural Engineering.

17.

Mehta

C. R.

Pandey

M. M.

Tiwari

P. S.

Gite

L. P.

Khadatkar

(2011). Tractor controls actuating force limits for Indian operators. Industrial Health, 49(4), 523–533. https://doi.org/10.2486/indhealth.MS1190

18.

Patel

Kumar

Mohan

(2000). Development of an ergonomic evaluation facility for Indian tractors. Applied Ergonomics, 31(3), 311–316. https://doi.org/10.1016/S0003-6870(99)00060-5

19.

Pheasant

S. T.

Harris

C. M.

(1982). Human strength in the operation of tractor pedals. Ergonomics, 25(1), 53–63. https://doi.org/10.1080/00140138208924926

20.

Raghavarao

(1983). Statistical techniques in agricultural and biological research. Oxford & Ibh Publishing.

21.

Roebuck

J. A.

Kroemer

K. H. E.

Thomson

W. G.

(1975). Engineering anthropometry methods. Wiley.

22.

Sen

R. N.

Nag

P. K.

Ray

G. G.

(1977). Some anthropometry of the people of Eastern India. Journal of the Indian Anthropological Society, 12, 201–208.

23.

Suutarinum

(1992). Tractor accidents and their prevention. International Journal of Industrial Ergonomics, 10(4), 321–329. https://doi.org/10.1016/0169-8141(92)90099-L

24.

Tewari

V. K.

Prasad

(2000). Optimum seat pan and back rest parameters for a comfortable tractor seat. Ergonomics, 43(2), 167–186. https://doi.org/10.1080/001401300184549

25.

Tiwari

(2001). Ergonomical evaluation of tractor operator’s workplace and activity [Unpublished master’s thesis] Jawaharlal Nehru Krishi Vishwa Vidyalaya.

26.

Yadav

(1995). Some ergonomical investigation on tractor operator workplace design [PhD thesis, Indian Institute of Technology, Kharagpur].

27.

Zander

(1972). Ergonomic in machine design: A case study of the self propelled combine harvester. H. Veenman & Zonen. https://library.wur.nl/WebQuery/wurpubs/fulltext/196525