the Problem (jack-knifing)
is the history of the problem?
type of bus is most popular because of the low floor and easy access for all
passengers, no steps! Every winter articulated buses are disabled due to jack-knifing
and the traction problems associated with pusher type articulated bus. Evidence
of this annual event can be seen in all cold climate cities of the world. A number of potential solutions have been
developed over the years, but the problem persists today.
long has it existed?
engine articulated busses were first introduced back in the 70s and 80s. There
popularity is now dominating the market, because of their easy access and high
productivity rates. But in winter they all suffer from the same inherited
design fault, which causes the bus to fold in half.
serious is the problem?
buses carry over 100 passengers so the potential risk of disaster is high. Road
safety is compromised with the vehicle losing control, crashing or
jack-knifing. Injuries to passengers and other road users are of a serious
concern. The images and web-links in this presentation are small example of
this global problem.
are the causes of the problem?
form the rear driving wheels combined with ice and snow, cause the vehicles middle
axle to loose traction, resulting in the bus jack-knifing. This usually happens
when the bus is moving forward from a standstill at low speed. These vehicles
operate faultlessly in good weather conditions.
are the effects of the problem?
the bus jack-knifes it is immobilized, this cause traffic jams and contributes
to following bus service being disrupted. Passengers are inconvenienced with services
being cancelled, which damage commuter confidence. This also leads to a loss of
revenue for the Bus Company and added expense in recovering the buses and stranded
are the symptoms of the problem?
wheels spinning and a loss of traction prevent the bus from moving forward. If
the bus does move forward and the centre non-drive axle looses traction, the
bus folds in the middle and jack-knifes. When this happens (in most cases) the
bus cannot free itself and has to wait for the tow truck.
methods have been used for dealing with the problem?
Snow chains and alternative tyres are being used to help with the traction
problem for the driving wheels.
A number of anti-jack-knifing devices have been designed for the prevention of jack-knifing of articulated
vehicles over the last decade. Obviously the devices haven’t solved the problem.
Recover vehicles are deployed to rescue stranded vehicles but they are usually
delayed, due to the resulting traffic jams and gridlock conditions.
are the limitations of those methods?
1) Snow chains can help with traction, but it doesn't prevent the bus from jack-knifing.