Whole-body vibration and ergonomic issues for bus drivers, UK

In document Managing risks to drivers in road transport (Page 176-180)

private transport company, Spain

3.3.17. Whole-body vibration and ergonomic issues for bus drivers, UK

Organisation(s): The UK Health and Safety Executive (HSE) and the Health and Safety

Laboratory (HSL)

Key Points

 Investigation of complaint of pins and needles in hands of bus driver.

 Assessing the level of vibration drivers are exposed to.

 Ergonomic assessment.

 Corrections to seat and driver’s posture and training for all drivers.

Introduction

Following a complaint about ‘pins and needles’ in the hands of a coach driver, the UK Health and Safety Executive commissioned the Health and Safety Laboratory (HSL) to investigate the likely cause. HSL scientists accompanied the driver for a day to observe his work activities and to assess the driver’s workstation in terms of:

 Whole-body vibration from the seat pan, how much of that vibration was transmitted by the seat, and how well the seat isolated the driver from the vibration

 Hand-arm vibration from the steering wheel.

 The workstation’s ergonomic design and its contribution to the driver’s posture, and the location of coach controls compared to the reach envelope.

Background

Professional drivers are susceptible to musculoskeletal disorders. These can be a result of prolonged sitting, poor posture, poor ergonomics, manual handling of luggage and in some cases whole-body vibration. Although whole-body vibration is more of a problem for drivers of off-road vehicles, it is possible for drivers of road vehicles to be exposed to levels of vibration or jolting which could lead to ill health or aggravate existing problems.

Aims

The aim of this work was to investigate the cause of the driver’s discomfort and to identify suitable measures to alleviate it.

Scope

The driver was asked to complete a questionnaire and was later interviewed to gain a clear understanding of the problem. The coach driver was male, aged 59, and drove the coach on a regular basis. He had been in his current employment for approximately two years but had been a coach driver for more than seven years. On average he drove for 21 hours a week. The driver had been experiencing pain in his hands for two years, since taking up his present employment and driving a particular coach. He reported that the pain began as a tingling sensation but became painful if he continued driving.

In an attempt to identify the cause, vibration and ergonomic data were generated while the driver travelled over a variety of road surfaces.

Vibration was measured on the steering wheel and simultaneously on the seat pan and at the base of the seat. By comparing the data generated at the seat pan and base, it was possible

to assess the seat’s damping effect. Previous studies have shown that poorly adjusted or faulty suspension seats can amplify vibrations.

Four main types of data were collected as part of the ergonomic assessment:

 Video of driver – to assess posture and driving style

 Wrist/hand movement data – this assesses whether the driver assumes poor wrist posture

 Pressure data – pads were put on the seat pan and seat back to provide further evidence of posture and the effects of driving on weight distribution

 Cab dimensions / driver anthropometry / driver questionnaire, to determine a. Where the driver fits, in terms of size, in the adult UK population, b. Background and personal details,

c. Whether the driver ‘fits’ the cab and whether it can be adjusted to suit him.

A review of the results showed that the seat damping was ineffective and actually amplified the vibrations. Upon closer inspection the seat’s suspension was found to be faulty. Despite these findings, the levels of vibration recorded were below the health guidance caution zone given in ISO 2631-1997.

The findings of the ergonomic assessment showed that there were a number of aspects of the coach’s cab and the driving posture it encouraged which presented hazards to the driver. The seating arrangement was central to these problems. Cab and seating measurements showed that the seat sloped forward at an angle of approximately 9 degrees. The data from the pressure pads showed that the driver’s weight was distributed unevenly on the seat pan with approximately 44% of the force on the seat being towards the rear third of the seat pan. The posture adopted due to the forward slope of the seat required the driver to support more weight through his legs and feet and through his hands on the steering wheel. The driver said that he had arranged the adjustable seat in this way after trying various options, and this initially seemed difficult to understand since it forced him into an unnatural posture that was hard work to maintain.

However, the video of the driver showed a significant vertical oscillation of the seat while the vehicle was in motion, as much as 6 or 7 cm. This was presumably due to the seat’s faulty damping and suspension mechanism. The extent of the vertical movement suggested that the driver may have arranged the seat so that his feet could remain on the pedals at all times. Had the angle of his thighs been more horizontal, any significant vertical motion of the seat could have lifted his feet off the pedals and made driving hazardous.

Whilst the driver’s seating arrangement overcame the problem of maintaining contact with the pedals, this forced him to lean forward, supporting more weight through his arms and hands. The driver was essentially pivoting around a point to the rear of the seat pan which meant that when either of his feet were lifted off the pedals, his arms had to support his weight. The position of his arms when driving supported this assessment.

Following these findings, the faulty seat was repaired and the company trained all their drivers how to adjust their seats to promote good posture and give good support. As a result the driver’s pins and needles disappeared.

Outcome and evaluation

 Vibration levels reduced through seat repairs and adjustment.

 Drivers trained to adjust seats to maximise support as well as minimise vibration.

Problems faced

Due to an intermittent fault on the seat cushion transducer, some data were not collected.

Success factors

 Ergonomic assessment which involved observation of the driver at work.

 Corrections to equipment combined with training.

 Simple measures to solve the problem and allow the driver to continue working.

Transferability

The types of measurements undertaken during this project could be performed on all vehicles. The fact that simple control measures can significantly reduce vibration levels, as illustrated in this case study, can be applied to many situations.

Further information HSL, Buxton, UK Alison Darby Email: Alison.Darby@hsl.gov.uk http://www.hse.gov.uk/research/rrpdf/rr612.pdf http://www.hse.gov.uk/research/crr_pdf/2001/crr01333.pdf

3.3.18.

Driver and Passenger Safety, Trojan Bus Campaign, First

Leeds, UK

Organisation: First UK Bus

Key points

 18 CCTV cameras fitted to buses.

 Plain-clothed police officers travel on buses.

 Police cars follow buses through troublesome areas.

 Offenders are apprehended and prosecuted.

 High-risk areas targeted.

Introduction

First Leeds Bus, in collaboration with West Yorkshire Police, used a ‘Trojan Bus’ fitted with 18 CCTV cameras to help apprehend the instigators of vandalism and violence. This was not only to protect drivers and passengers, but also to act as a deterrent with the long-term aim of reducing such incidents.

Background

First Leeds Bus drivers and passengers have been injured by missiles thrown at passing buses by youths in some areas of Leeds. These incidents not only cause injuries; they also raise stress levels for drivers and deter people from travelling by bus. Repair costs are also an issue.

The Trojan Bus initiative launched by First Leeds in conjunction with West Yorkshire Police in March 2008 was intended to identify youths throwing missiles at passing buses and others on board intimidating passengers and causing damage.

Scope

The Trojan Bus is a single-deck bus that has been specially adapted to carry 18 CCTV cameras, and it operates on routes through known high-risk areas for vandalism and missile- throwing.

The First Leeds management team puts the Trojan Bus on routes where vandalism or other incidents have been reported to the police. Minimal planning was needed to put the bus into service and the only investment required was the cost of installing the CCTV cameras. The Trojan Bus operates as a normal service carrying fare-paying passengers. At the request of West Yorkshire Police, plain-clothed officers travel on the bus and an unmarked police car follows behind to assist in the pursuit and arrest of missile throwers or vandals.

The bus’s existence was publicised through the press to raise public awareness of the project, both to reassure passengers and deter offenders.

Drivers were briefed on the project, how the bus was equipped, etc., but no project-specific training was necessary.

First UK Bus also provides conflict management training for its drivers and buses are equipped with assault screens and ‘spit kits’ used to collect saliva samples for DNA analysis. First UK Bus also actively encourages the police to charge offenders.

Outcomes and evaluation

Since the Trojan Bus has been deployed there have been three arrests which have led to prosecutions. Drivers have welcomed the initiative and now feel safer while performing their duties. This partnership with West Yorkshire Police has led to further collaboration with the force on other security issues.

Problems faced

This was a relatively straightforward project and no significant problems have been reported.

Success factors

 Collaboration and support of police.

 Targeting high-risk areas.

 No disruption to passenger services.

 Support of drivers.

 Further security measures supported by the police.

Transferability

With the support of the police this initiative could be easily implemented in any passenger transport company. When compared to the potential injuries and costs of repairs, it requires minimal investment and little or no disruption to passenger services.

Further information

MrDavid Mercer

In document Managing risks to drivers in road transport (Page 176-180)