Information AboutJackknifing |
| CATEGORIES ABOUT JACKKNIFING | |
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Jackknifing is actually not very common and usually only happens to an empty vehicle. Most truck drivers are skilful enough to correct a skid before it becomes a jackknife. It would be an exaggeration to claim that jackknifing accounts for 5% of Tractor-semitrailer accidents since in many cases it's the collision that would have caused the vehicle to jackknife and not vice versa. Radio stations often report jackknifed trucks because people phone to tell them, but more often than not, the truck hasn't technically jackknifed. It's just stuck in the snow or crashed etc.. HOW TO AVOID JACKKNIFING The way to avoid jackknifing is the same as to avoid a skid. # Keep your distance, especially on a slippery road surface. # Spread your braking over the longest possible distance. # Don't decelerate on a turn (or a bend). Brake in a straight line before the turn (or bend) and slow down a little more than necessary. You can then increase your speed as you make the turn. This procedure is even more important on a downhill turn. # Braking and swerving at the same time is a major cause of jackknifing. If evasive action has to be taken it would be better (if at all possible) to brake first and not to swerve until the last moment, or better still to release the brakes in order to swerve, then re-apply them. #If the tractor begins to skid, it should be corrected in exactly the same way as with a rigid vehicle by releasing the brakes and steering into the skid. This must be done before the skid becomes a jackknife. Caravans If you drive a car and Caravan it's important, not only to keep your distance, but not to go too fast, especially downhill. You must be aware that if you brake hard the caravan pushing from behind could raise the rear-end of the car off the road and spin it round until it faces the other way. Caravans often overturn after jackknifing lifting the rear of the car completely off the road. Electromagnetic retarders An Electromagnetic Retarder such as a "Telma" normally acts on the propeller shaft of a vehicle and can be used to slow a vehicle down or hold it back on a steep descent keeping the brakes fresh for an emergency. Since the retarder only acts on the drive axle, '''misuse could cause jackknifing'''. The retarder should only be applied with caution when driving an empty articulated vehicle on a slippery surface. The lever in the cab has several degrees of braking. It should be applied gradually, one position at a time and released immediately if the axle locks up. Some of the latest retarders are however designed to release and re-apply automatically in a similar way to Anti-lock Brakes . (Some retarders can also be set to hold a vehicle back at a speed pre-set by the driver. This is done by moving the lever into the first position at the required speed.) Some trailers are fitted with an electromagnetic retarder. If this is applied by itself the vehicle can be slowed down without fear of jackknifing but it could cause trailer swing. TRAILER SWING When a trailer skids to one side, this is known as a trailer swing or '''trailer slew'''. This could happen on a slippery road surface, often where there is a camber. '''This is not the same as jackknifing''' and is not serious since the trailer moves back into line as the vehicle continues forwards. The driver must be aware however, that the trailer could slide up against parked cars or the wheels could slide into a ditch. ANTI JACKKNIFIE DEVICES Over the years systems to combat jackknifing have been developed.
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