Page 12 - Trucker's guide - engelsk

Driving on slippery roads
We have a number of narrow, winding and steep roads in Norway. Heavy vehicles are more likely to get into trouble on slippery roads than smaller vehicles. Long, heavy and wide tractor-trailer combinations are particularly vulnerable.
Large vehicles frequently need to move all the way out to the edge of the road to
allow oncoming traffic to pass safely. It is important to watch your speed and have good tyres and brakes in order to maintain a safe and steady course in such situations.
Winding roads and steep inclines require you to continually adjust your speed and manoeuvre your vehicle for the safety of other road users. Your driving must always be adjusted to suit the amount of grip available on the road.
Trailer skidding
With tractor-trailer combinations, the trailer is frequ- ently the cause of hazardous situations and makes driving on slippery roads particularly challenging.
When long and heavy vehicles skid, this is a serious and demanding situation. It is difficult to regain con- trol. It may take a long time and require a lot of space on the road. Remember, it is better to steer your tractor-trailer combination into a ditch than to collide with oncoming traffic.
Particular causes of skidding trailers:
• High speed
• Cornering
• Braking
• A lot of slush on the road
• Tyres unsuitable for winter conditions
• The wheels on the right-hand side going off the
edge of the road
• ABS malfunctions
• EBS malfunctions?
Incorrect adjustment of brakes between the tractor unit and the trailer, uneven weight distribution of the cargo and uneven road surfaces are also factors that can cause both the trailer and the tractor unit to skid.
In the case of semitrailer combinations, it is particularly important to ensure that the fifth wheel pivots easily so that inertia does not prevent the tractor unit turning.
Safe operation of tractor-trailer combinations on slip- pery roads requires you to be cautious and assess conditions, the road and traffic. It is also important to ensure that the vehicle is in good condition.
Serious accidents as a result of trailers skidding usually occur when the trailer skids into the path of oncoming traffic.
Slippery descents
On long descents in winter, drivers may find that the road surface at the bottom of the hill is more slippery than at the top. Therefore, before starting your des- cent you need to:
• carefully assess the road conditions
• decide whether you need to use chains • determine the appropriate speed
• make sure the “ROAD IS CLEAR!”
If you use chains, you must take into account the weight distribution of your cargo.
A heavy load towards the front of the vehicle, combi- ned with powerful auxiliary brakes that are applied to the driven wheels only, may cause the driven whe- els to skid. To prevent this, you can attach chains to the driven wheels (see Figure 1).
A heavy load towards the rear of the vehicle may cause the front wheels to skid, making the vehicle difficult to steer. To prevent this, you sometimes have to attach chains to one of the front wheels to help with steering. This may be particularly relevant to vehicles with tandem axles and semitrailers.
Raising the tandem axle behind the driving axle makes it more difficult to steer the vehicle on slip- pery road surfaces (see Figure 2).
When driving on slippery roads, as much of the weight as possible should be on the motor vehicle as this could reduce the risk of jackknifing and will improve traffic flow. You may need to use chains on the trailer’s wheels to prevent the trailer skidding, and to ensure sufficient stability and braking on downhill gradients.
On slippery roads, the service brake system is more effective than the auxiliary brake as the auxiliary brake only act on the driven wheels. However, bear in mind the dangers of overheated brakes and brake failure.
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Trucker’s Guide