Multi-combination theory course

RULES OF BRAKING

Brake in plenty of time (i.e. early and gently, never savagely)

Brake firmly, only when travelling in a straight line.
Vary the brake pedal pressure according to the condition of the road surface.
When descending a steep winding hill, brake firmly on the straight stretches and ease off in the bends. Remember the value of engaging a low gear early in the descent.
NOTE: Rarely do brakes fail on heavy vehicles going downhill. Usually it is the driver that is at fault for not selecting a sufficiently low enough gear to maintain a safe constant speed for the descent requiring minimum, if any, use of the service brake. This can cause the brakes to overheat, which may result in brake failure or a fire.

REASONS WHY BRAKING FIRMLY SHOULD BE PERFORMED WITHIN A STRAIGHT LINE:

When the brakes are applied to a moving vehicle, the weight is thrown forward and downward onto the front wheels and the rear tends to lift. The resulting unequal distribution of weight makes steering heavier and reduces the general stability of the vehicle, especially at the rear wheels.

This stability rapidly decreases in a corner as a result of the centrifugal forces generated by the cornering vehicle.

WEIGHT

SKIDDING
DEFINITION:
An involuntary movement of a vehicle due to the grip of the tyres on the road becoming less than the force or forces acting on the vehicle.

Or

A vehicle skids when one or more of the wheels slide instead of having pure rolling action.

CAUSES OF SKIDDING:

• 
  Excessive speed for conditions
  

• 
  Sudden or excessive braking
  

• 
  Harsh or excessive acceleration
  

• 
  A rapid change of direction; or
  

• 
  A combination of all or any of the above
  

FACTORS THAT INCREASE THE RISK OF SKIDDING:

• 
  Ice, snow, leaves oil or fuel on the road
  

• 
  Water (aquaplaning), loose surface, corrugations or potholes
  

• 
  Adverse camber, downhill slopes
  

• 
  Bald or poorly inflated tyres
  

• 
  Suspension faults, steering mechanism faults
  

• 
  Painted lines and arrows, metal inspection plates, steel plates covering road works
  

• 
  Panic
  

• 
  Poor load distribution
  

• 
  Brake adjustment/truck-trailer bias
  

REACTION AND BRAKING
REACTION
REACTION TIME:
Reaction time is the time between the moment the driver observes the need for action and actually starts to take that action.

REACTION DISTANCE:

Reaction distance is the distance travelled in the reaction time.

Reaction distance increases at the same rate as the speed of the vehicle increases.
To calculate reaction distance, multiply the reaction time (in seconds) by speed (in metres per second). REACTION DISTANCE = REACTION TIME x SPEED

(METRES) (SECONDS) (METRES/SECOND)

BRAKING

BRAKING DISTANCE:

The distance taken to stop the vehicle once the brakes have been applied. This can be influenced by factors such as downhill gradients, which may increase the distance, or uphill gradients which may reduce the braking distance. Also wet or slippery roads, uneven or unsealed roads will affect the distances.

The braking distance, being the distance taken to stop once the brakes have been applied, increases at a proportionally greater rate as the speed rises. As the speed doubles (X2) the braking distance increases by four times (X4). The reason for this is that the distance taken to stop is proportionate to the square of the speed so if the distance taken to stop from 30km/h is 5 metres, the distance taken from 60km/h will be 20 metres (twice the speed, four times the distance).
The braking distances of commercial vehicles can vary depending on the weight that is being carried. A lightly loaded vehicle can sometimes take a greater distance to stop as there is less weight or down force on the tyres to create the friction needed between tyre and road surface, and a fully loaded vehicle may also take further to stop, as the brakes have to deal with the greater weight.
Excessive use of the brakes can cause a build up of heat at the brakes leading to a loss of effectiveness and increased stopping distances so supplementary braking systems such as engine or exhaust brakes should be considered when descending steep hills.

HEAVY VEHICLE DIMENSIONS
MAXIMUM LENGTH OF A RIGID VEHICLE:
A rigid vehicle, except an articulated or controlled access bus, must not exceed 12.5 metres in length (including any overhang).



Illustration of:

• 
  front projection limits; and
  
• 
  rear overhang limit from vehicle standards; and
  
• 
  maximum rear projection of load allowed without a warning signal.
  

COMBINATIONS

MAXIMUM LENGTH OF VEHICLES:
An articulated vehicle (semi-trailer) must not exceed 19 metres in length (including any overhang).


19 metres


HEAVY VEHICLE DIMENSIONS (continued)

A B-DOUBLE MUST NOT EXCEED 25 METRES IN LENGTH

However, the operation of B-Doubles up to 26 metres in length is allowed subject to:

• 
  the combination must not be over 26 metres in length; and
  
• 
  the distance between the point of articulation at the front of the lead semi trailer and the rear of the combination is not over 20.6 metres in length; and
  
• 
  the prime mover of the combination is fitted with a complying Front Underrun Protective Device; and
  
• 
  if the prime mover is manufactured after 31 December 2005 it is fitted with a complying protective cab; and
  
• 
  the prime mover does not have a load carrying area.
  

A B-TRIPLE MUST NOT EXCEED 36.5 METRES IN LENGTH
A DOUBLE ROAD TRAIN MUST NOT EXCEED 36.5 METRES IN LENGTH
A TRIPLE ROAD TRAIN MUST NOT EXCEED 53.5 METRES IN LENGTH

A LONG VEHICLE is any vehicle that, together with any load or projection, is 7.5 metres long or longer.
An ARTICULATED BUS is a bus consisting of more that one rigid section with passenger access between the sections and the sections connected to one another so as to allow rotary movement between the sections and must not exceed 18 metres in length.
A COMPLYING BUS is a bus with 2 or 3 axles and a single steer axle that is fitted with a compliance plate indicating that it was manufactured during or after July 1994 and meets the emergency exit specifications (ADR44); meets the rollover strength specifications (ADR59); meets the occupant protection specifications (ADR68) and is equipped with an approved air suspension system.

HEAVY VEHICLE DIMENSIONS (continued)
MAXIMUM WIDTH OF VEHICLES:
The maximum width of a vehicle is 2.5 metres (including any load)


REAR VISION MIRRORS:
A rear vision mirror fitted to a motor vehicle with a GVM over 3.5 tonnes must not project over 150 millimetres beyond the widest part (excluding lights, signalling devices and reflectors) of the vehicle or combination;

However, the rear vision mirror may project not over 230 millimetres beyond the widest part of the vehicle or combination if it can fold to project not over 150 millimetres beyond the widest part.

Loads On Vehicles – Side Overhang The maximum side overhang of a load on a vehicle is 150 mm providing the overall width does not exceed 2.5 metres.

HEAVY VEHICLE DIMENSIONS (continued)
MAXIMUM HEIGHT OF VEHICLES:
A VEHICLE MUST NOT EXCEED 4.3 METRES IN HEIGHT.
However:

• 
  A vehicle built to carry cattle, sheep, pigs or horses must not exceed 4.6 metres in height.
  
• 
  A car carrier must not exceed 4.6 metres in height when loaded.
  
• 
  A double-deck bus must not exceed 4.4 metres in height.
  

CAR CARRIER

REAR OVERHANG:
The distance measured at right angles between the rear overhang line of a trailer carrying vehicles on more than one deck and the rear of the rearmost vehicle on the trailer must not exceed 4.9 metres.

HEAVY VEHICLE DIMENSIONS (continued)

LOAD PROJECTION:


More than 1.2 metres
flag (day) or light (night)

Flag (day) or light (night)

REAR PROJECTION:

1. 
   The rear of a load on a vehicle must carry a warning signal if the load:
   

• 
  projects more than 1.2 metres behind the vehicle; or
  
  
  

• 
  projects to the rear of the vehicle so that the end of the load cannot be seen easily from behind; or
  

• 
  is on a pole-type trailer.
  

2. In daytime, the warning signal must be a brightly coloured flag or a piece of material, with each side at least 300 millimetres long.

3. In the night-time, the warning signal must be a red light which can be seen for 200 metres.
REAR MARKER REFLECTOR PLATES
All vehicles with a gross vehicle mass (GVM) exceeding 12 tonnes, and all trailers with a gross vehicle mass (GVM) exceeding 10 tonnes must be fitted with two retro-reflective rear marker plates.





VARIOUS REFLECTOR TYPES




DO NOT OVERTAKE TURNING VEHICLE signs may be displayed on long vehicles, (vehicles over 7.5 metres in length). If incorporated on the rear marker plate, must be displayed on the left side of the rear of the vehicle.

PORTABLE REFLECTORS (TRIANGLES)under 80kmp
A person must not drive a motor vehicle with a GVM over 12 tonnes unless the vehicle is equipped with at least 3 portable warning triangles.

If a driver stops on a road and the vehicle is not visible at any time for at least 200 metres in all directions from the vehicle, the driver must use at least 3 portable warning triangles positioned, as detailed below, to warn other road users of the vehicle.

If some or all of any load being carried by the vehicle falls onto a road and is not clearly visible at any time for at least 200 metres in all directions from the fallen load, the driver must use at least 3 portable warning triangles positioned, as detailed below, to warn other road users of the fallen load.

The requirement for positioning the triangles is:

• 
  1 triangle positioned at least 50 metres, but not over 150 metres, in front of the vehicle or fallen load; and
  

• 
  1 triangle positioned at least 50 metres, but not over 150 metres, behind the vehicle or fallen load; and
  

• 
  1 triangle positioned at the side of the vehicle, or fallen load that gives sufficient warning to other road users of the position of the vehicle or fallen load.
  

PERMIT VEHICLES CONFIGURATIONS