APPSC AMVI key terms

The radius of the smallest circle a vehicle can trace with its outer front wheel while steering fully, used to judge manoeuvrability in tight spaces and traffic.

A linkage arrangement in which the inner front wheel turns through a larger angle than the outer one, so all wheels roll about a common centre without tyre scrub.

The horizontal distance between the centre of the front axle and the centre of the rear axle, influencing weight distribution, stability and turning behaviour.

The single point at which the whole weight of a vehicle may be assumed to act; its height and position govern rollover tendency and load transfer.

The angle between a tyre's actual direction of travel and the direction its wheel plane points, arising from lateral tyre deflection during cornering.

A handling condition where the front tyres lose grip first, so the vehicle turns less sharply than the driver intends and tends to run wide.

A handling condition where the rear tyres lose grip first, causing the rear of the vehicle to swing outward and the vehicle to turn more sharply than commanded.

The speed at which a vehicle rotates about its vertical axis, usually expressed in degrees per second and central to electronic stability control logic.

A system that compares driver steering input with measured yaw rate and selectively brakes individual wheels and reduces engine torque to correct skids.

A system that rapidly modulates brake pressure at each wheel to prevent wheel lock-up, preserving steering control and shortening stopping distance on low-friction surfaces.

The temporary loss of braking effectiveness caused by overheating of friction linings or brake fluid, often after repeated or prolonged hard braking.

The share of heat energy generated during braking that is absorbed and dissipated by the brake assembly rather than transferred to surrounding components.

The ratio of the cylinder volume above the piston at bottom dead centre to the volume at top dead centre, affecting power output, efficiency and knock tendency.

The ratio of the actual volume of air-fuel mixture drawn into the cylinder per cycle to the theoretical swept volume, indicating how well the engine breathes.

An exhaust-driven compressor that forces extra air into the engine cylinders, increasing power density; it is driven by a turbine in the exhaust stream.

Abnormal combustion in a spark-ignition engine in which the end gas ignites spontaneously before the flame front reaches it, producing a sharp metallic sound and possible damage.

A measure of a petrol's resistance to knocking, comparing its behaviour with reference mixtures of iso-octane and normal heptane under standard test conditions.

An indicator of the ignition quality of diesel fuel, expressing how readily it self-ignites under compression compared with reference hydrocarbons.

India's staged vehicle exhaust emission standards, aligned with European norms, that set permissible limits for pollutants from new vehicles and fuels.

An after-treatment method in which a urea-based reagent is injected into the exhaust to convert nitrogen oxides into nitrogen and water over a catalyst.

A porous ceramic device in the exhaust that traps soot particles from diesel engines and periodically burns them off through regeneration.

Fine solid and liquid particles suspended in exhaust gas, including soot and unburnt hydrocarbons, linked to respiratory illness and visible as smoke.

Loss of positive drive through a clutch because the friction surfaces cannot transmit the engine torque, causing engine speed to rise without matching road speed.

A fluid coupling with a stator that multiplies engine torque at low speed and allows the engine to idle while the vehicle is stationary.

The gear ratio between the gearbox output and the driven wheels, determining the trade-off between top speed and tractive effort.

A gear train that distributes drive to two wheels while allowing them to rotate at different speeds when the vehicle turns a corner.

A differential that deliberately restricts the speed difference between driven wheels, improving traction when one wheel encounters a slippery surface.

The tilt of the steering axis from vertical in side view; positive caster gives self-centring of the steering and improves straight-line stability.

The inward tilt of the kingpin or strut axis in front view, which reduces scrub radius and helps return the wheels to straight ahead.

The force opposing motion caused by deformation of the tyre and road surface at the contact patch, increasing with load and decreasing with higher inflation pressure.

The lateral force generated at the tyre contact patch when a wheel travels at a slip angle, enabling the vehicle to follow a curved path.

A body's resistance to change in its rotational motion, equal to the sum of each mass element multiplied by the square of its distance from the axis.

A device that automatically regulates engine speed by adjusting fuel supply or throttle opening as load changes, maintaining a set speed.

The turning moment produced when a spinning body such as a flywheel or wheel is forced to change the orientation of its axis of rotation.

The provision that makes driving or attempting to drive a motor vehicle with blood alcohol above the prescribed limit an offence punishable with fine and imprisonment.

An instrument that estimates blood alcohol concentration from a breath sample, used by enforcement officers as preliminary evidence in drunken-driving cases.

The written record police prepare on receiving information about a cognisable offence, which sets the investigation of a road accident in motion.

Interpretation of tyre marks left at an accident scene to estimate vehicle paths, braking onset and pre-impact speed using friction and length relationships.

The dimensionless ratio of the frictional force between two surfaces to the normal force pressing them together, governing maximum braking deceleration.

The interval between a driver perceiving a hazard and applying the brake, during which the vehicle continues at its original speed.

The total distance a vehicle travels during the driver's reaction time plus the braking distance, used to set safe geometric design standards for roads.

A common measure that converts mixed traffic into equivalent car units for capacity analysis, reflecting the road space a vehicle type effectively occupies.