1.2. General Classification of Automobiles
The different types of automobiles found on roads are presented in Chart 1.1 in a comprehen-
sive manner. There are in general three main classifications of the various types of vehicle. They
are:
(i) The single-unit vehicles or load carriers.
(ii) The articulated vehicles.
{Hi) The heavy tractor vehicles.
Chart 1.1. Classification of vehicles.
1.2.1. The Single-unit Vehicles or Load Carriers
These vehicles are conventional four-wheel types with two-axle design in which the front
axle is a steering non-driving axle and the rear axle is the driving axle. With the advancement,
many changes have been incorporated in the number of axles as well as the driving system.
1.2.2. The Articulated Vehicles
A larger powered three-wheeler with single steering wheel in front and a conventional
rear-driving axle falls in this category. It can be turned about its own tail due to the three-wheel
construction and has a greater handling ability in unusual places. The coupling mechanism
between semi-trailer and tractor in most of these vehicles is designed for automatic connection
and coupling up. A lever is provided within the driver’s approachTor coupling operation. A pair
of retractable wheels in front can be raised or lowered automatically along with the coupling
and uncoupling operation.
1.2.3. The Heavy-tractor Vehicles
To move heavy loads tractor or independent tractor vehicles are used. They commonly
operate in pair either in tendon or as puller or pusher. The latter arrangement provides stability
while descending appreciable gradients.
The digital figures like 4×2, 4×4, 6×4 etc. are commonly used in the classification of
vehicles, where the first figure represents the total number of wheels and the second figure the
number of driving wheels. By increasing the number of axles, the load per axle can be reduced,
which protects the tyres from overloading and the road surface from damage. Wheel axles are
called “live” if drive and called “dead” if non-drive. A live axle supports the payload and provides
driving tractive effort, whereas a dead axle just supports the load.
