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Heavy rigid vehicle stability and dynamics

An introduction programme for drivers of heavy motor vehicles.

Heavy rigid vehicle stability and dynamics: an introduction programme for drivers of heavy motor vehicles

6.   Driver factors


6.1   Steering

Steering

It is important to have two hands on the steering wheel whenever it is possible. This applies not only during turns and cornering but also when travelling on straight roads. A driver who adopts a relaxed, two-handed steering style responds more readily to normal vehicle movement than one who consistently leaves one hand off the wheel.

The effects on vehicle handling that occur as a result of the steering actions of the driver must not be underestimated, particularly by those who operate vehicles carrying high-CG loads.


6.2   The system of vehicle control

When negotiating intersections, roundabouts and other potential hazards such as road works, railway crossings and crash sites, it's important to control the vehicle's speed and side-cornering forces before entering the site.

Drivers who use the system of vehicle control will be concentrating on potential trouble spots, not on the brakes and gear lever.

While the system of vehicle control does take some getting used to, once perfected it produces an unrushed, deliberate and safe driving style that reduces the risks, particularly at intersections and even more so at roundabouts, where three changes in direction can occur and vehicles carrying high-CG or ‘live’ loads often come to grief. In these situations the combination of road camber and running trailer wheels onto kerbs can make the stability problems even worse. The system of vehicle control is explained below.

Vehicle control

1   Course

  • Know where you are going and put the vehicle in the correct place on the road.

2   Mirrors

  • Check behind the vehicle and along both sides.

3   Signal

  • Indicate your intentions for at least three seconds before you carry out any manoeuvre.

4   Brake

  • Adjust your road speed early so you can downshift.

5   Gears

  • Change down, and repeat the process if necessary, so that you are in the right gear before you manoeuvre.

6   Mirrors

  • Check your mirrors again.

7   Execute

  • Carry out the manoeuvre.

8   Accelerate

  • Accelerate away from the turn or hazard.

A very cautious and planned approach to corners is always necessary.