Let's clear the air

          Innovative Transport Solutions Pty Ltd

Status; New Concept: 

Hydraulic Traction Drive  (HTD) for articulated buses.


To solve the traction problems of the rear engine articulated buses and prevent jack-knifing

 The you-tube  videos below best explain the jack-knifing problem that has existed for some decades.


Readers may not be aware that only the rear axle drives these buses. This is the same drive-line as used in a standard 40-foot bus. To compound the traction problem, the articulated bus is 20-foot longer and much heavier. 

The rear engine articulated buses all suffer from the same basic design fault. In bad weather conditions, the torque from the rear drive axle pushing forward, causes the center non-drive axle to break traction, resulting in the bus folding in half and producing the familiar jack-knife position. This action is a bit like trying to push a linked chain. 

The bus is usually immobilized when this happens and it requires a tow truck to get home, passengers walk home. 

Image below is a typical pose of a jack-knifed bus

The product is designed as an aftermarket conversion kit, that prevents the articulated bus from jack-knifing and improves traction.

Image at left is of a typical 2 wheel drive or 6x2 rear engine articulated bus.  

Image at left features the Hydraulic Traction Drive conversion kit. 
The bus is transformed into a 4-wheel drive or 6x4 articulated bus.


Images of Pusher Articulated buses in Distress

The standard pusher or rear engine articulated bus has a serious design floor, it is unable to function in slippery or snow bound situations. The bus cannot be driven in the snow or icy conditions, it is like trying to push a linked chain.




The above video shows that even in light snow conditions a small incline will stop a pusher type articulated bus



Ice road truckers are no match for snow bus drivers.


Analysing the Problem (jack-knifing)

What is the history of the problem? 

This 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.

How long has it existed?

Rear 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.

How serious is the problem?

These 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.

What are the causes of the problem?

Thrust 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.

What are the effects of the problem?

When 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 passengers.

What are the symptoms of the problem?

Rear 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.

What methods have been used for dealing with the problem?

1) Snow chains and alternative tyres are being used to help with the traction problem for the driving wheels.

2) 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.

3) Recover vehicles are deployed to rescue stranded vehicles but they are usually delayed, due to the resulting traffic jams and gridlock conditions.

What are the limitations of those methods?

1) Snow chains can help with traction, but it doesn't prevent the bus from jack-knifing. 
2) Vehicles fitted with anti jack-knifing remedies are still prone to folding in half. 
3) In the winter season the tow truck fleet is overburdened with calls for help from all types of vehicles, resulting in long recovery times for the stranded bus. The recovery vehicles also fall victim to traffic congestion caused by the stranded buses.

Above image is of the 3 most popular articulated bus power-train