مطالعه ارگونومیک ارتعاشات کل بدن از لوکوموتیو های راه آهن ایالات متحده

US locomotive operators have exposure to multi-axis whole-body vibration (WBV) and shocks while seated. This study assessed operator-related and ergonomic seating design factors that may have confounding or mitigating influence on WBV exposure and its effects. Vibration exposure was measured according to international guidelines (ISO 2631-1; 1997); ergonomic work place factors and vibration effects were studied with a cross-sectional survey instrument distributed to a randomly selected group of railroad engineers (n=2546n=2546) and a control group; and during vehicle inspections. The survey response rate was 47% for the RR engineers (n=1195n=1195) and 41% for the controls (n=323n=323). Results of the mean basic vibration measurements were for the x, y, z-direction and vector sum 0.14, 0.22, 0.28 and 0.49 m/s2 respectively; almost all crest factors (CF), MTVV and VDV values were above the critical ratios given in ISO 2631-1. The prevalence of serious neck and lower back disorders among locomotive engineers was found to be nearly double that of the sedentary control group without such exposure. Railroad engineers rated their seats mostly unacceptable regarding different adjustment and comfort aspects (3.02–3.51; scale 1=excellent to 4=unacceptable), while the control group rated their chairs more favorably (1.96–3.44). Existing cab and seat design in locomotives can result in prolonged forced awkward spinal posture of the operator combined with WBV exposure. In a logistic regression analysis, time at work being bothered by vibration (h/day) was significantly associated with an increased risk of low back pain, shoulder and neck pain, and sciatic pain among railroad engineers. Customized vibration attenuation seats and improved cab design of the locomotive controls should be further investigated.

In the European Union the risk of excessive whole-body vibration (WBV) exposure has been recognized and specific requirements regarding WBV exposure prevention have been introduced [1]. However, there is a paucity of information about the WBV exposure and working conditions of locomotive engineers in the generally available vibration and occupational health literature. One of the reasons is that this industry has been very reluctant in the past to study such issues and provide access to the work place. It appears that locomotive engineers and conductors are working in a unique environment with likely exposure to significant WBV and shocks depending on locomotive design, train speeds, and operational tasks [2] and [3]. In a recent epidemiological study of active North-American railroad (RR) engineers, the prevalence of serious type neck and lower back disorders was found to be nearly double that of a sedentary control group without such exposure [4], although the basic vibration levels appear to be lower compared to some road and off-road vehicles with high vibrations levels and back disorder risks. Ergonomic and seating conditions are important and possible modifying factors in an overall risk assessment of WBV exposure [5] and [6] and for musculoskeletal health in occupational medicine [7]. The goal of this study was the description and evaluation of cab and seating conditions in US built locomotives, including the subjective rating of seats and vibration effects by the locomotive engineers. Furthermore, the operational tasks that may be important and modifying factors in the risk assessment of WBV and prevention are reviewed.

This study demonstrated a close relationship of WBV exposure duration and neck and lower back problems in RR engineers. Although the mean basic vibration levels measured in the US locomotives appeared to be lower in comparison with some road and off-road vehicles with a known high risk for lower back disorders and other problems [11] and [12], the unique seating conditions, the locomotive operator's awkward body posture and likely the shock content of the vibration appeared to play an important factor in the overall assessment. Over the last century, it appears, there has been little change in basic concepts of locomotive cab and seat design in North America. For the most part any changes of the cab and seat design were driven by technical and operational requirements, structural/collision safety issues and vehicle design needs due to conversion from coal/steam to diesel-electric or electric power. Human factor requirements, operators’ comfort and convenience, and in particular operator protection from harmful vibration and shocks appeared to have played a minor role in the current evolution of locomotive cabs, control stands and seating [13]. There are two basic locomotive cab design concepts in use in road or yard service locomotive engines: the ‘Association of American Railroad (AAR) Control Stand’ and the front consol in newer generation ‘wide-body locomotives’. The yard locomotive engines are operated bi-directionally and the operator has to adjust and change the seating position frequently for the different driving directions (Fig. 1 and Fig. 2).