Jackknifes: not always the driver’s fault

While drivers of heavy articulated vehicles are often blamed when their vehicles jackknife, sometimes these incidents are beyond their control

Two recent horrific road accidents in the Roodepoort area of Gauteng involving heavy-duty articulated vehicles that jackknifed and spilled their entire loads into the road, prompted me to write this article. After both accidents the roads, were closed for several hours, resulting in massive traffic delays and very frustrated motorists.

The general public is always very quick to blame the driver for an incident like this, which is not always fair as there are a number of factors that can cause an articulated vehicle to jackknife, and some of these are entirely beyond the control of the driver.

A lack of proper truck tractor and trailer maintenance can cause a vehicle to jackknife, especially when the trailer brakes are no longer functioning properly, due to poor maintenance, or because the trailer and truck tractor brakes are not correctly balanced. Poor truck and trailer maintenance cannot be blamed on the driver.

Many jackknifing incidents occur when a frustrated or impatient passenger car or bakkie driver, who is irritated by the slow moving traffic, races past the truck and trailer and then swerves in front of the truck and fills the safety gap that the truck driver has created in order to be able to stop his rig safely when the traffic ahead slows down or stops.

Many passenger car drivers are not aware that a car or bakkie has a much shorter stopping distance than a fully loaded heavy articulated vehicle.

When the truck driver’s safe stopping gap has been drastically reduced by the irresponsible behaviour of a car or bakkie driver, and the traffic suddenly comes to a halt, the truck driver’s natural reaction is to apply brakes and swerve to the left or right to avoid hitting the vehicle in front.

The truck tractor is then in a turning position, while the loaded trailer is still moving in a straight line. This is one of the many situations that could cause the articulated truck to jackknife.

While the drivers of articulated vehicles have no control of the abovementioned factors, they are, however, in control of certain factors that can cause the vehicle to jackknife. These include:

• When the driver ignores the road sign limiting heavy vehicles from using a road and proceeds to use that road.

• When descending down steep gradients without adopting the proper procedure and driving techniques to retard the vehicle, ensuring that the foundation brakes on the vehicle do not overheat, which could cause brake failure.

• When the driver selects the incorrect gear. This would normally happen when the vehicle is descending a steep hill and the driver changes into a lower gear with a gear ratio that is too low for the speed at which the vehicle is travelling, and then suddenly releases the clutch. The rear drive wheels then lock and the trailer continues in a straight line, resulting in a jackknife.

• When driving too fast in very poor weather conditions.

• When the driver enters a sharp curve in the road too fast and halfway into the curve he or she applies harsh braking.

The braking systems that are fitted to the modern truck tractors sold in South Africa today are perfectly adequate and well balanced to stop any rig in a straight line without jackknifing, provided that the vehicle is well maintained and the driver is well trained.

Published by

Vic Oliver

Vic Oliver is one of this country’s most respected commercial vehicle industry authorities, and has been in this industry for over 50 years. Before joining the FOCUS team, he spent 15 years with Nissan Diesel (now UD Trucks), 11 years with Busaf and seven years with International.
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