Reducing Whole Body Vibration to Improve the Safety and Health of Bus Drivers

On the road every day, transportation workers are responsible for the safe delivery of passengers, materials and goods across the United States. Bus drivers ensure our kids and family members arrive safely. Bus drivers are vital to our economy, but their job can put them at increased risk for health problems. In 2014, musculoskeletal disorders accounted for 23% (n=3,400) of all injuries and illnesses resulting in days away from work for bus drivers.¹

Bus drivers are vulnerable to health risks as their job requires long hours sitting while absorbing vehicle vibrations from the roads and highways. Whole body vibration occurs as a vehicle travels over roads and the vibrations are transferred through the floor of the vehicle or seat into the driver’s legs and spine. Vehicle design, type of driver seat including suspension and seat cushions can affect exposure to whole body vibration. The major impact of whole body vibration is the development of musculoskeletal disorders, most commonly lower back pain, although upper extremity disorders such aches and pains and weakness in the arm, shoulder, or the neck can occur as well.² Research has also shown that whole body vibration contributes to other negative health effects including cardiovascular, gastrointestinal, nervous and urological disorders.³ It is important to understand how to minimize exposure to whole body vibration to reduce negative health effects on bus drivers.

The Study

To address whole body vibration exposure, researchers set out to determine the contribution of bus type on whole body vibration. ⁴ Two different buses, a high-floor bus mainly used for longer commuter routes and a low-floor bus often used as intercity buses with easy entry and exit for passengers, were driven to compare whether performance differences existed.  Both buses were driven on a standardized route which included four road types to represent typical terrain for bus drivers: newer smooth freeway, rough older freeway, city streets and roads with speed bumps. Different drivers drove each bus with 12 professional bus drivers operating the high-floor bus and 15 professional bus drivers operating the low-floor bus. The buses used the same brand new, air-suspension seat, and no passengers were onboard.  Whole body vibration exposures were evaluated using two international standards, ISO 2631-1 (1997) and ISO 2631-5 (2004) to assess human exposure and multiple shocks.

The Results

Researchers analyzed floor vibration and whole body vibration exposure by road type. Whole body vibration differed significantly by road type. In both buses whole body vibration exposure was greatest on roads with speed bumps and lowest on smooth freeway. The high-floor bus had less whole body vibration exposure on freeways and city streets but greater whole body vibration exposure on roads with speed bumps. The brand new air-suspension seat only reduced 10% of the floor vibration in both buses.

The Conclusion and Looking Ahead

Road type impacts whole body vibration in both the low-floor and high-floor buses. Researchers recommend assigning buses to the appropriate routes. On routes that contain speed bumps operate a low-floor bus.  Either bus would be appropriate on freeways and city streets.

Research is underway to examine various seat suspension technologies and their ability to minimize whole body vibration exposures to professional vehicle operators. Similar to bus drivers, truck drivers are at risk for exposure to whole body vibration. New active and air seat suspension technology will be examined in trucks.

NIOSH wants to hear from you!

What are the challenges to mapping new routes to avoid rough roads?

Peter W. Johnson, PhD, MS, Professor at University of Washington

Stephen D. Hudock, PhD, CSP, Manager of the NIOSH Musculoskeletal Health Cross-Sector

Thomas McDowell, PhD, Research Industrial Engineer in NIOSH Health Effects Laboratory Division

Elizabeth Dalsey, MA, Health Communication Specialist in the NIOSH Western States Division

References

¹ U.S. Census Bureau for the U.S. Bureau of Labor Statistics (BLS), Injuries, Illnesses and Fatalities: http://www.bls.gov/iif/

² Lewis and Johnson P. (2012) Whole-body vibration exposure in metropolitan bus drivers. Occupational Medicine, 62: 519 – 525

³ Okunribido, O., Magnusson, M., Pope, M.H., 2008. The role of whole body vibration, posture and manual materials handling as risk factors for low back pain in occupational drivers. Ergonomics 51 (3), 308-329.

⁴ Blood RP, Ploger JD, and Johnson PW. (2010)  Whole body vibration exposures in forklift drivers: a comparison of a mechanical and air-ride seat. Ergonomics, 53 (11): 1385 – 1394.