posted 5 years ago

Volvo Consigns Jack-knifing To History

Why A Lorry Jack-knives

Excellent: Volvo has created a revolutionary system that minimises the risk of a truck and its trailer jack-knifing. So, let us consider a scenario. A heavy load is travelling down a hill that is covered by patches of ice. The haulier sees a parked car so brakes to ensure he/she passes at a sensible speed. Under normal circumstances the truck/trailer slow at the same rate - but this time the truck slows faster than its bedfellow. Why? Because the latter has hit ice and is struggling to find the required traction to lose momentum. It is therefore moving faster than the truck so forces itself alongside. This is more likely to occur on a bend than on a straight stretch of road. As the truck/trailer are connected they then fold against each other like a half closed penknife. Clearly, this is one of the most challenging problems a haulier can face. Also, even if he/she has the skill to recover the situation there might not be enough room as the roads are littered with hazards such as cars, pedestrians, bikes, etc. Volvo's new system – rather than making it easier to control a jack-knifing vehicle – operates by preventing the phenomenon in the first place. But how?

Volvo Stretch Brake System

The Volvo Stretch Brake System is activated by the hauler as he/she approaches a steep decent. Operation typically comes via a lever behind the steering wheel that resembles an indicator stalk. Its function is available while travelling at forty kilometres or less. Once activated – and the haulier releases the throttle – the system automatically pulses the trailer's brakes, i.e. on for a moment, off for a moment, then back on. This prevents it picking-up more speed than the towing vehicle and trying to force its way alongside and into a jack-knife. The system can be deactivated once the gradient of the road is comparatively flat. According to the Volvo Trucks Accident Research Team that specialises in road safety, about sixty accidents that involved trucks in Sweden in 2012 could have been prevented with the Stretch Brake System. As such, if every heavy goods vehicle on the planet – and perhaps every vehicle towing a caravan or trailer - had such a system it could save countless lives. Furthermore, motorists might arrive at their destinations less stressed as one of today's motoring nightmares would be a thing of the past. Excellent. 


From Eric's comment it sounds like training may not be what it was. Hardly surprising. In these modern days of ABS, normal car drivers rarely have any proper training on how to use the brakes and make use of engine braking....

Be much better if it automatically activated and deactivated.

Anti-jack knife devices have been on the market for years this is just a re-hash

Up until the 1980s all Scandinavian trucks were fitted with independant trailer brakes. Some genius in Brussels decided they were not a good idea.

In 1956 I use to teach learner drivers to drive Magarus lorries towing an 3 ton eyelet trailor. On the steering colum was a stalk which applied the trailor brakes. You taught them to say trailor brakes first when applying the brakes. u

Now if we can get the police to start requiring cars to have a safe (at least 2 seconds) distance before they pull in front of the trucks, especially in construction zones...Most accidents I have seen involving trucks are caused by motorists failing to have proper distance before pulling in front of the trucks, so the trucks had no room to brake in an emergency.