Evaluation of whole-body vibration exposure experienced by operators of a compact wheel loader according to ISO 2631-1:1997 and ISO 2631-5:2004

Limited studies were carried out to evaluate the whole-body vibration (WBV) exposure experienced by operators of compact wheel loaders (CWLs) according to ISO 2631-1:1997. No study was carried out according to ISO 2631-5:2004. Therefore, evaluation of the WBV exposure using these two standards was carried out and the results were compared in this study. Tri-axial accelerations were measured at the seat/operator interface on a medium-sized CWL. The vibration measurements were carried out in ten different operations, such as the V-cycle and the driving over different road surfaces. In order to represent the daily work of the CWL, seven scenarios were proposed. These scenarios are comprised of V-cycle and driving over different distances. The evaluation result according to ISO 2631-1:1997 showed that the permitted daily exposure durations of six scenarios estimated using the vibration dose value (VDV) method did not exceed 8 h. For the pure V-cycle and the combination of V-cycle and slow driving, the permitted daily exposure durations estimated according to ISO 2631-1:1997 were shorter than those estimated according to ISO 2631-5:2004. However, for the combination of V-cycle and fast driving, the permitted daily exposure durations estimated according to ISO 2631-1:1997 were longer than those estimated according to ISO 2631-5:2004.Relevance to industryThis study evaluated the effect of WBV arising from a CWL on human health according to ISO 2631-1:1997 and ISO 2631-5:2004. Evaluation results show that boundaries of the health guidance caution zone in ISO 2631-5:2004 are higher than those in ISO 2631-1:1997.     

Vibration and shock exposure of maintenance-of-way vehicles in the railroad industry

The aim of this study is to investigate and compare vibration and shock measurements of maintenance-of-way vehicles used in the railroad industry for track maintenance and construction. Following international standards (i.e., ISO 2631-1: 1997) and professional guidelines the frequency weighted root-mean-square (r.m.s.) acceleration for each measurement axis, the vector sum, the seat effective amplitude transmissibility (SEAT), the crest factor (CF), the maximum transient vibration value (MTVV), the vibration dose value (VDV), the ratio and the newly proposed shock risk estimation factor ‘R’ for spinal injury according to ISO 2631-5:2004 were measured and calculated for seven different maintenance-of-way vehicles during revenue service. Furthermore, a proposed alternative spinal injury prediction method, the VibRisk model, which incorporates different typical driver postures and operator physical characteristics was included for comparison with the ISO 2631-5 risk prediction. The results of the vibration exposure measurements depended on vehicle type, track/surface conditions and seat properties, with the tamper and bulldozer showing the highest r.m.s. vibration values. The vector sum (a_v) results ranged from 0.37 to 0.99 (m/s²). Five of seven track maintenance vehicles would exceed the current Whole-body Vibration ACGIH-TLV^® guideline for an 8 h exposure duration in the vertical axis recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). The measured CF, MTVV/a_w and VDV/(a_w·T^1/4) ratios were at or above the critical ratios in the majority of measurements given by the ISO 2631-1 (1997) and American industry guidelines by the American Conference of Governmental Industrial Hygienists (ACGIH-TLV). Comparing both prediction models for vibration shock risk for parts of the lumbar spine, different risk predictions and inconsistencies were found. The VibRisk model generally suggests different and higher risk of vertebral endplate failure for individual lumbar levels, whereas the ISO 2631-5 model indicated generally lower risks and did not differentiate between different disk levels and driver posture. Epidemiological studies validating the different shock risk models are lacking. Work modifications and adequate suspension seats would be beneficial for prevention of harmful exposure to vibration and shocks.     

A cohort study of sciatic pain and measures of internal spinal load in professional drivers

In a prospective cohort study of 537 male professional drivers, the occurrence of sciatic pain showed stronger associations with measures of internal lumbar load expressed in terms of daily compressive dose, S_ed (MPa), and risk factor, R (non-dimensional), according to ISO/WD 2631-5 (2013), than with measures of daily vibration exposure calculated as either 8-h energy-equivalent frequency-weighted acceleration (ms^? 2 r.m.s.) or vibration dose value (ms^? 1.75) according to the EU Directive on mechanical vibration (2002). Herniated lumbar disc, previous lumbar trauma and physical work load were also powerful predictors of the occurrence of sciatic pain over time. Psychosocial work environment was poorly associated with sciatic pain. The boundary values of risk factor (R) for low and high probabilities of adverse health effects on the lumbar spine, as proposed by international standard ISO/WD 2631-5 (2013), tend to underestimate the health risk in professional drivers.     

Whole-body vibration experienced by haulage truck operators in surface mining operations: A comparison of various analysis methods utilized in the prediction of health risks

Whole body vibration (WBV) was measured on eight surface haulage trucks in three size classes (35, 100, 150 ton haul capacities). Vibration was measured at the seat/operator interface in accordance with the ISO 2631-1 standard during 1 h of normal operation. Highest acceleration readings were observed in the z-axis (vertical). Estimated equivalent daily exposure values in the range of 0.44–0.82 ms^?2 were observed using the frequency-weighted r.m.s method and 8.7–16.4 ms^?1.75 using the vibration dose value method. Assessment was carried out using ISO 2631-1 and 2631-5. Operators of surface haulage trucks are regularly exposed to WBV levels that exceed safety limits as dictated by the ISO 2631-1 standard. However, according to ISO 2631-5 the probability of an adverse health effect remains low. These findings confirm an apparent disagreement between the two analysis methods.     

Predicting the health risks related to whole-body vibration and shock: a comparison of alternative assessment methods for high-acceleration events in vehicles

In this paper, alternative assessment methods for whole-body vibration and shocks are compared by means of 70 vibration samples measured from 13 work vehicles, deliberately selected to represent periods containing shocks. Five methodologies (ISO 2631-1:1997, BS 6841:1987, ISO 2631-5:2004, DIN SPEC 45697:2012 and one specified by Gunston [2011], ‘G-method’) were applied to the vibration samples. In order to compare different evaluation metrics, limiting exposures were determined by calculating times to reach the upper limit thresholds given in the methods. Over 10-fold shorter times to exposure thresholds were obtained for the tri-axial VDV (BS 6841) than for the dominant r.m.s. (ISO 2631-1) when exposures were of high magnitude or contained substantial shocks. Under these exposure conditions, the sixth power approaches (ISO 2631-5, DIN SPEC, G-method) are more stringent than a fourth power VDV method. The r.m.s. method may lead to misleading outcomes especially if a lengthy measurement includes a small number of severe impacts. In conclusion, methodologies produce different evaluations of the vibration severity depending on the exposure characteristics, and the correct method must be selected.     

Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631–1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s² and 0.14 rad/s². The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631–1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable.

Statement of Relevance: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.     

Whole body vibration exposures in bus drivers: A comparison between a high-floor coach and a low-floor city bus

Low back pain (LBP) is common in occupational bus drivers and studies have shown a dose–response relationship between whole body vibration (WBV) exposure and LBP. Bus design may be an important factor in determining the WBV exposure a bus driver receives. The purpose of this study was to determine whether differences exist in WBV exposures between two buses commonly used in long urban commuter routes: a high-floor coach and a low-floor city bus. Each bus was driven over a standardized test route which included four road types: a newer smooth freeway, a rougher old freeway, a city street segment, and a road segment containing several speed humps. WBV exposures were calculated per ISO 2631-1 (1997) and ISO 2631-5 (2004) standards. WBV exposures were significantly higher in the high-floor coach bus on the road segment containing speed humps. There were primarily small differences between buses in WBV exposures encountered on the city street and freeway segments. With respect to the ISO 2631-1 and European Union's A(8) and VDV(8) action limit values, both buses could be operated on the smooth freeway without exceeding the 8-hour action limits but would have to be operated less than 8 h when operating on the other road types. On average, the seats only attenuated 10% of the floor transmitted vibration and amplified the vibration exposures on the speed humps. Due to the low vibration attenuation performance of the bus driver's seat, evaluating different types of seats and seat suspensions may be merited.Relevance to industryLow back Pain (LBP) is one of the leading causes for workplace disability; therefore, it would be beneficial for employers and workers to minimize WBV exposures resulting in LBP. To reduce WBV exposures, buses should be assigned to appropriate routes and drivers should rotate across routes to vary continuous and impulsive exposures.     

Transmission characteristics of suspension seats in multi-axis vibration environments

The multi-axis vibration transmission characteristics of selected suspension seats were investigated in the laboratory. Subjects were exposed to a flat acceleration spectrum and two low frequency signals extracted from multi-axis acceleration data recorded at the floor of a passenger locomotive. Triaxial accelerations were measured at the floor of the vibration table and at the interfaces between the subject and mounted seat (seat pan and seat back). The transmission ratios between the overall seat pan and seat back accelerations and floor accelerations provided an effective tool for evaluating the effects of measurement site, vibration direction, and posture among the selected seating systems. The results showed that the system transfer matrix, estimated using a multiple-input/single-output model, would be less than ideal for predicting low frequency operational seat vibration when using suspension seats. The Seat Effective Amplitude Transmissibility (SEAT), estimated for the tested locomotive seats, was used to predict the weighted seat pan accelerations and Vibration Total Values for assessing a 1-h operational exposure in accordance with ISO 2631-1: 1997.

Relevance to industry

Multi-axis SEAT values can be estimated for seating systems tested in the laboratory using representative operational exposures. These values can be applied to monitored vehicle floor accelerations to target potentially harmful vibration in accordance with ISO 2631-1: 1997, assuming the operational exposures have similar frequency and magnitude characteristics. The transmission at the seat back should be considered when substantial low frequency multi-axis vibration is present.     

Comparison of some technical methods for the evaluation of whole-body vibration

The aim of the investigation was to compare physical measurements of vibrations transmitted through the driver's seat to operators of off-road forestry machines, with the driver's subjective evaluation of discomfort from vibration in different driving situations. Physical measurements and analyses were performed in accordance with ISO-standard 2631 and amendments (ISO/TC 108/SC4/N60). A total of 13 different vibration analysis methods were considered. The investigation consisted of seven studies. The machines were driven on five test tracks, each consisting of six to ten shorter intervals representing easy to moderately difficult terrain conditions. Subjective ratings correlated better with technical evaluations based on the two most dominant vibration directions or all three directions than with only the critical direction according to ISO 2631. Calculations based on vibration energy in the entire frequency range 1–80 Hz gave better correlation than calculations based on energy in the critical frequency band according to ISO 2631. The weighted sum of vector method gave the best correlation with subjective ratings. The correlation coefficient for this method was clearly higher than with the method recommended in ISO 2631, i.e. 1–3-octaveband critical direction and frequency.     

Measures of internal lumbar load in professional drivers – the use of a whole-body finite-element model for the evaluation of adverse health effects of multi-axis vibration

The present study aimed to (1) employ the method for evaluation of vibration containing multiple shocks according to ISO/CD 2631–5:2014 (Model 1) and DIN SPEC 45697:2012 in a cohort of 537 professional drivers, (2) deliver the results for a re-analysis of epidemiological data obtained in the VIBRISKS study, (3) clarify the extent to which vibration acceleration and individual variables influence risk values, such as the daily compressive dose S_ed and the risk factor R, and (4) compare the results with in vivo measurements and those obtained in previous studies with similar models. The risk factor R was influenced by the acceleration, lifetime exposure duration, sitting posture, age at the start of exposure and body mass/body mass index in order of decreasing effect. Age and annual and daily exposure duration had only a marginal effect. The daily compressive dose S_ed and the risk factor R showed weak linear association with the daily vibration exposure A(8) and the vibration dose value VDV. The study revealed high shear forces in the lumbar spine.     

Measurement and evaluation of whole‐body vibration exposure in drivers of cargo vehicle compositions

The present study carries out measurements and evaluations of whole‐body vibration (WBV) exposure in drivers of a cargo vehicle composition, traveling under different conditions of roads and loading, to compare and assess the health risk through the various criteria provided by vibration exposure standards. Using the acceleration data measured in the seat, the WBV exposure of the drivers is evaluated according to the criteria provided by five standards: three different versions of ISO 2631 (Part 1, 1985 and 1997; Part 5, 2004), the European Directive 2002/44/EC and the new Brazilian regulation NR‐15 published in 2014. Comparisons investigating the differences between the standards are presented. The results of the experimental data indicate that the current version of the NR‐15 is more restrictive than the other standards considered in this paper. Thus, these results can contribute to improve the criteria used in the new NR‐15.     

Whole-body vibration exposure experienced by motorcycle riders – An evaluation according to ISO 2631-1 and ISO 2631-5 standards

Riders of twelve motorcycles, comprising 6 full-scale motorbikes and 6 motor-scooters, and 5 sedan vehicles, performed test runs on a 20.6 km paved road composed of 5 km, 5 km, and 10.6 km of rural, provincial and urban routes, respectively. Each test run of motorcycle was separately performed under speed limits of 55 km/h and 40 km/h. Tri-axial accelerations of whole-body vibration (WBV) were obtained by using a seat pad and a portable data logger, and the driver's view was videotaped with a portable media recorder. Root mean square (RMS) acceleration, 8-h estimated vibration dose value (VDV₍₈₎) and 8-h estimated daily dose of static compression dose (S_ed) were determined from the collected data in accordance with ISO 2631-1 and ISO 2631-5 standards. Experimental results indicate that the WBV values of the sedan vehicle drivers have low RMS, VDV₍₈₎ and S_ed values (RMS 0.27–0.32 m/s²; VDV₍₈₎ 6.3–8.3 m/s^1.75; S_ed 0.21–0.26 MPa). However, over 90% of the motorcycle riders had VDV₍₈₎ (mean 23.5 m/s^1.75) exceeding the upper boundary of health guidance caution zone (17 m/s^1.75) recommended by ISO 2631-1, or had S_ed (mean 1.17 MPa) exceeding the value associated with a high probability of adverse health effects (0.8 MPa) recommended by ISO 2631-5. Over 50% of the motorcycle riders reached these boundary values for VDV and S_e in less than 2 h. The WBV exposure levels of the full-scale motorbikes riders and motor-scooter riders were not significantly different. However, the RMS and VDV₍₈₎ values of motorcycle riders indicate significant roadway effect (p < 0.001), while their S_ed values indicate significant speed limit effect (p < 0.05). This study concludes that the WBV exposure levels of common motorcycle riders are distinctively higher than those of sedans, even on a regular paved road. The impact on health of WBV exposure in motorcycle riders should be carefully addressed with reference to ISO 2631-1 and ISO 2631-5.

Relevance to industry

This study compares the predicted health risks of motorcycle riders according to ISO 2631-1 and ISO 2631-5 standards. Experimental data suggest that the vibration dose value of ISO 2631-1 and daily dose of equivalent static compression stress of ISO 2631-5 have roughly equivalent boundaries for probable health effects.     

City bus driving and low back pain: a study of the exposures to posture demands, manual materials handling and whole-body vibration

A cross-sectional study was conducted to investigate worker exposure to posture demands, manual materials handling (MMH) and whole body vibration as risks for low back pain (LBP). Using validated questionnaire, information about driving experience, driving (sitting) posture MMH, and health history was obtained from 80 city bus drivers. Twelve drivers were observed during their service route driving (at least one complete round trip) and vibration measurements were obtained at the seat and according to the recommendations of ISO 2631 (1997), for three models of bus (a mini-bus, a single-decker bus, a double-decker bus). The results showed that city bus drivers spend about 60% of the daily work time actually driving, often with the torso straight or unsupported, perform occasional and light MMH, and experience discomforting shock/jerking vibration events. Transient and mild LBP (not likely to interfere with work or customary levels of activity) was found to be prevalent among the drivers and a need for ergonomic evaluation of the drivers' seat was suggested.     

Low-back disorders in agricultural tractor drivers exposed to whole-body vibration and postural stress

The occurrence of low-back pain (LBP) was investigated in a population of 1155 tractor drivers exposed to whole-body vibration (WBV) and postural stress (response rate 91.2%) and in a control group of 220 office workers (response rate 92.2%). The subjects were questioned about several types of low-back symptom (LBP, sciatic pain, acute LBP, transient and chronic LBP) and various work- and individual-related risk factors, by using a standardized questionnaire. Vibration measurements were performed on a representative sample of the vehicles driven by the tractor drivers in the last ten years. Vibration magnitude and duration of exposure were used to calculate a vibration dose for each tractor driver. Perceived postural load was assessed in terms of frequency and/or duration of awkward postures at work. The prevalence of LBP was found to be greater in the tractor drivers than in the controls. After controlling for potential confounders by logistic modelling, low-back disorders were found to be significantly associated with both vibration dose and postural load. Back accidents and age were also significant predictors for LBP. Quantitative regression analysis indicated that vibration exposure and postural load were independent contributors to the increased risk for LBP according to a multiplicative model. The exposure levels for WBV recently recommended by a proposal of European Directive on physical agents seem to be more adequate to prevent long-term health effects on the lower back than the exposure limits suggested by the International Standard ISO 2631/1.     

Measurement of whole‐body vibration exposure from unsuspended cabin tractor semi‐trailers

Indian tractor semi‐trailer drivers are exposed to mechanical whole‐body vibration during their work. Some drivers suffer from low‐back pain from this vibration. However, there is no evidence of a relationship between the whole‐body vibration from tractor semi‐trailers and low‐back pain or occupational disease because of the lack of investigations. A field study was conducted to characterize the health risks associated with driving tractor semi‐trailers. Studies were conducted at different loadings and on different road surfaces as well as at different speeds, with the vibrations measured at the driver–seat interface on x‐longitudinal, y‐transverse and z‐vertical axes. The vibrations were compared with the health‐risk guidance according to Annex B of ISO 2631‐1 (ISO 2631/1, 1997). The findings of this study indicated that Indian tractor semi‐trailer drivers should not operate continuously more than 4 h a day under current working conditions. © 2011 Wiley Periodicals, Inc.     

Hand-transmitted vibration from the steering wheel to drivers of a small four-wheel drive tractor

The paper presents research results of the vibration transmitted from the steering wheel of the small tractor with a 4-wheel drive to the driver's hands. The vibration measurements were carried out on the tractor randomly chosen from the producer's store-house. Before testing the tractor was examined and adjusted following the producer's recommendations. The vibration levels were measured at idling and at full load. The vibration level on the steering wheel was measured and analyzed and the frequency spectra for the chosen working conditions were obtained. The frequency-weighted acceleration, given in m/s(-2), was calculated. The vibration total value was defined as the root-mean-square of the three component values. The obtained values are graphically represented in accordance with ISO/DIS 5349-1979 and ISO5349-1-2001. The vibration exposure for the predicted 10% prevalance of vibration-induced white finger in accordance with Annex C of the same standard was also tested.     

Effects of seat structural dynamics on current ride comfort criteria

The ISO 2631-1 (1997 ISO 2631-1 (International Organisation for Standardisation). 1997. Mechanical Vibration and Shock – Evaluation of Human Exposure to Whole-Body Vibration – Part 1: General Requirements. Geneva: ISO 2631-1, International Organisation for Standardisation. [Google Scholar]) provides methodologies for assessment of the seated human body comfort in response to vibrations. The standard covers various conditions such as frequency content, direction and location of the transmission of the vibration to the human body. However, the effects of seat structural dynamics mode shapes and corresponding resonances have not been discussed. This study provides important knowledge about the effects of vehicle seat structural vibration modes on discomfort assessment. The occupied seat resonant frequencies and corresponding vibration modes were measured and comfort test was carried out based on the paired comparison test method. The results show that the ISO 2631-1 (1997 ISO 2631-1 (International Organisation for Standardisation). 1997. Mechanical Vibration and Shock – Evaluation of Human Exposure to Whole-Body Vibration – Part 1: General Requirements. Geneva: ISO 2631-1, International Organisation for Standardisation. [Google Scholar]) method significantly underestimates the vibration discomfort level around the occupied seat twisting resonant frequencies. This underestimation is mainly due to the ISO suggested location of the accelerometer pad on the seatback. The centre of the seatback is a nodal point at the seat twisting mode. Therefore, it underestimates the total vibration transferred to the occupant body from the seatback.     

Influence of tyre inflation pressure on whole-body vibrations transmitted to the operator in a cut-to-length timber harvester

The influence of tyre inflation pressure on whole-body vibrations transmitted to the operator during the movement of a cut-to-length timber harvester was evaluated. Vibration measurements were taken in three orthogonal (x, y, z) axes at tyre pressure settings of 138, 345 and 414 kPa. Vibration was predominant in the vertical (z) direction with the peak rms acceleration value for the operator seat (0.281 ms(-2)) occurring at approximately 3.2 Hz.The corresponding peak value for the operator cabin chassis was 0.425 m s(-2) at 4 Hz.At 414 kPa, there was potential health risk on the operator for exposures above 8h duration. The vibration total values recorded for the operator seat at the maximum tyre inflation pressure setting were classed as "fairly uncomfortable" (ISO standard 2631-1), and vertical seat vibration transmissibility was highest between 4 and 8 Hz at the 345 kPa tyre pressure setting. The recorded values of WBV were significantly reduced by a reduction in tyre inflation pressure which may therefore be used to moderate the magnitude of WBV on wheeled timber harvesters.     

The whole-body vibration in operation of wheeled and tracked harvester IN PINUS thinning

Technological advances available in wood harvesting machines have provided productivity improvements and more comfort in forestry operations. However, operators may be exposed to whole-body vibration which can lead to a wide variety of health disorders and industry losses. This research aimed to evaluate the exposure of workers to whole-body vibration in thinning harvesting operations comparing two models of harvesters (tracked and wheeled) working in Pinus taeda stands submitted to the first commercial thinning. Whole-body vibration was determined by the three orthogonal axes (X, Y, and Z) using a 3-Axis integrator vibration meter, and the data were analyzed according to the criteria established by the ISO 2631–1:1997 and the European Directive, 2002/44/EC, concerning the resulting acceleration from normalized exposure A (8) and value of the resulting vibration dose value (VDV). The acceleration and vibration levels obtained by the tracked harvester presented mean values of A (8) of 0.6 m/s² and VDV 11.2 m/s^1.75, while by the wheeled harvester, mean values were A (8) of 0.4 m/s² and VDV 9.3 m/s^1.75, respectively. It was possible to verify the expressive vibration from the tracked harvester analysis, the operators were exposed to the whole-body vibration above the limits recommended by the regulating norms.