Overturning tractors and other self-propelled vehicles

What you should know

All vehicles can overturn.  Accidents on slopes are not confined to hilly or mountainous regions.  They happen just as easily on or near banks, ditches, drains, ramps, uneven or flat ground.  Vehicles can also overturn on artificial slopes such as ramps, or when performing tasks such as rolling silage,

When working on slopes the main risks are:

• Loss of control
  This occurs when wheels lose traction rending the brakes and steering ineffective.  It it easier to lose control of a vehicle on a slope because of the effect of gravity and forward momentum.
• Runaways
  Loss of control can lead to a runaway where the vehicle starts to move down the slope and the driver is unable to bring it back under control
• Jack-knifing
  This happens when a trailer or trailed appliance pushes into the tractor and slews the tractor round.  Poor ground conditions, heavy loading and poor wheel grip increase the risk
• Overturns
  A vehicle may overturn sideways eg when attempting to traverse across a slope diagonally, or trying to turn down a slope as a consequence of a runaway and jack knife.  Machines can also overturn forwards or backwards depending on the situation.

What you need to do

1.  Plan the job.

Before working on slopes you should assess the risks.  Factors to consider include:

• Gradient
  Different vehicles have different capabilities.  Gradients on a slope can vary with some parts steeper than others.
• surface
  Different surfaces can affect how well a vehicle can deal with a slope eg grass, earth, loose stones
• Ground conditions
  A slope that is safe during dry conditions may become unsafe if wet, waterlogged, frozen or thawing.  Uneven ground with ruts, pot holes and deep tracks can affect stability
• Weather
  Wet and windy weather may increase the risks
• Obstacles
  Tree stumps and rocks may be struck, particularly when hidden by vegetation, and cause sideways overturns if struck on the uphill side
• Task
  The proposed task will also affect the risk.  When using rear mounted spreaders the load will decrease during spreading and this will reduce rear wheel grip. Tractors with trailed rollers, four-wheel trailers etc will have extra thrust imposed with no additional weight – they may slide away out of control.

2.  Select a suitable vehicle fitted with a roll over protective structure (ROPS)

A roll bar or safety cab is designed to provide protection for the operator if the vehicle overturns.  Where roll over protection is fitted, you should also have a lap belt or seat restraint fitted if a machine will be used in situations where there is a risk of overturning.

• check that the roll bar or safety cab is in good condition and correctly fitted. Corrosion and incorrect mounting bolts can cause them  to fail in an overturn;
• never remove windows or doors from a safety cab;
• fit a lap belt where one has not  been installed as original equipment;

To reduce the risk of an overturn:

• make sure that tractors and machines are properly equipped and maintained, especially brakes, steering and tyres. Consider wide wheel settings for work on slopes;
• select a machine suitable for the job.  Tractors with four wheel drive are likely to be safer to use on slopes compared to those with two wheel drive.

You may only use a tractor or self-propelled machine without ROPS in low-risk situations such as buildings and orchards or where specific exemptions exist.

3.  Work safely

Always use safe systems of work when working on slopes.  For example:

• you should turn uphill when working across a slope, and descend straight down the gentlest gradient;
• you cannot always safely descend a slope that you safely drove up;
• select an appropriate gear and speed
• take into account working with trailers, attachments and loads will change the centre of gravity

To reduce the risk of injury from an overturn:

• stay in the cab and do not try to jump clear, as most deaths and serious injuries involve those who are crushed when they jump or are thrown out of a cab during overturning;
• don't carry loose items such as draw bar pins or tools inside the cab as they become projectiles and  may cause extra injury in an overturn.
• wear the lap belt or seat restraint

Anyone who is required to drive on slopes should receive adequate training so they are aware of the hazards, understand the factors influencing the risks and are able to perform safe driving techniques.