Vehicle metrics
Encyclopedia
There are a broad range of metrics that denote the relative capabilities of various vehicle
s. Most of them apply to all vehicles while others are type-specific.
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
s. Most of them apply to all vehicles while others are type-specific.
| Measurement | English unit | Metric unit | Affects | General preference | Notes |
|---|---|---|---|---|---|
| 0 to 60 mph 0 to 60 mph The time it takes to accelerate from 0 to 60 mph is a commonly used performance measure for automotive acceleration in the United States and the United Kingdom. In the rest of the world 0 to 100 km/h is used... |
seconds | seconds | acceleration Acceleration In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ... |
lower is better | |
| 0 to 100 to 0 mph | seconds | seconds | acceleration & braking | lower is better | formerly common in British publications |
| Braking distance Braking distance Braking distance refers to the distance a vehicle will travel from the point where its brakes are fully applied to when it comes to a complete stop... |
feet | meters | safety Safety Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be... |
shorter is better | |
| Brake specific fuel consumption Brake specific fuel consumption Brake Specific Fuel Consumption is a measure of fuel efficiency within a shaft reciprocating engine.It is the rate of fuel consumption divided by the power produced. It may also be thought of as power-specific fuel consumption, for this reason... |
lb/(hp·h) | g/(kW·h) | economics Economics Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"... , range |
lower is better | |
| Drag coefficient Drag coefficient In fluid dynamics, the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or... |
(ratio) | (ratio) | economics, top speed, range | lower is better | |
| Frontal cross-section area | sq ft | m2 | economics, top speed, range | lower is better | if area is too small, vehicle becomes difficult to use |
| Fuel economy Fuel economy in automobiles Fuel usage in automobiles refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed.... |
mpg | l/100 km and km/L | economics, range | greater is better (mpg and km/L), lower is better (L/100 km) | must be specified on new vehicles for sale in the US & UK |
| Maximum g-force G-force The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and... (s) |
g or ft/s2 | g or m/s2 | acceleration | higher is usually better | measures cornering, braking or forward acceleration |
| Ground pressure Ground pressure Ground pressure is the pressure exerted on the ground by the tires or tracks of a motorized vehicle, and is one measure of its potential mobility, especially over soft ground. Ground pressure is measured in pascals which corresponds to the EES unit of pounds per square inch... |
psi Pounds per square inch The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units... |
pascals Pascal (unit) The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre... |
traction | lower is better in soft ground, reduces bogging; higher with loose surface | has greater impact on off-road vehicle Off-road vehicle An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks... s |
| Lift to drag ratio | - | - | economics, range | higher is better for aircraft | improved by narrow, long wings |
| Power-to-weight ratio Power-to-weight ratio Power-to-weight ratio is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources... |
hp/lb | W/kg | acceleration | higher is better | |
| Polar moment Polar moment of inertia Polar moment of inertia is a quantity used to predict an object's ability to resist torsion, in objects with an invariant circular cross section and no significant warping or out-of-plane deformation. It is used to calculate the angular displacement of an object subjected to a torque... |
psi (lb·sq ft) | kg·m2 | handling Car handling Automobile handling and vehicle handling are descriptions of the way wheeled vehicles perform transverse to their direction of motion, particularly during cornering and swerving. It also includes their stability when moving at rest. Handling and braking are the major components of a vehicle's... |
lower permits quicker turn-in for cars, higher is more stable in straight line. | The moment of inertia about a vertical axis of a vehicle |
| Propulsive efficiency Propulsive efficiency In aircraft and rocket design, overall propulsive efficiency \eta is the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due to air drag, gravity, and acceleration. It can also be stated as the proportion of the... |
% | % | economics, range | higher is better | For rockets and aircraft, percent of the energy contained in a vehicle's propellant converted into useful energy, |
| Roll center Roll center The roll center of a vehicle is the notional point at which the cornering forces in the suspension are reacted to the vehicle body.-Theory:There are two definitions of roll center... |
inches | mm | handling | Too many variables to state a general preference. | |
| Rolling friction | - | - | economics | lower is better | improved by narrow, high pressure tires |
| Specific fuel consumption (thrust) | lb/(lbf·h) | kg/(kgf·h) or g/(kN·s) | economics, range | lower is better (for any given speed) | in airbreathing jet engine Jet engine A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets... s it is improved by using more inert air for propulsion (i.e. lower exhaust velocity), in rockets, higher exhaust velocity |
| Shift time Shift time Shift time refers to the time interval between gear changes in a transmission during which power delivery is interrupted. This is usually in reference to motor vehicles but can apply to any gearbox. Reducing shift time is important in performance vehicles or race cars because during shifting the... |
mSec | ms | acceleration | lower is better | for vehicles equipped with automatic transmission Automatic transmission An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually... s |
| Specific fuel consumption (shaft engine) | lb/(hp·h) | kg/(kW·h) | economics, range | lower is better | for shaft engines less fuel use for a given output power means higher efficiency |
| specific impulse Specific impulse Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,... |
seconds | seconds or kN·s/kg | economics, delta-v Delta-v In astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver.... /range |
higher is typically better | in airbreathing jet engine Jet engine A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets... s it is improved by using more inert air for propulsion (i.e. lower exhaust velocity), in rockets, higher exhaust velocity |
| Top speed | mph MPH MPH is a three-letter acronym that refers to miles per hour, a measurement of speedMPH may also refer to:* Make Poverty History, a campaign supported by Bob Geldof to end poverty in Africa... |
km/h | Maximum rate of straight line travel Speed In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as... |
higher is better | Electronically limited in some cars for safety (mostly due to concerns of tire failure at high speed) |
| Weight Weight In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:... |
lb | kg | acceleration, braking distance Braking distance Braking distance refers to the distance a vehicle will travel from the point where its brakes are fully applied to when it comes to a complete stop... |
lower is better | |
| Weight distribution Weight distribution Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes, and trains.In a vehicle which relies on gravity in some way, weight distribution directly affects a variety of vehicle characteristics, including handling, acceleration, traction, and component life... |
% | % | handling, acceleration, traction Traction (engineering) Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:... |
close to 50:50 (%Front:%Rear) is commonly considered better | |
| Gross axle weight rating Gross axle weight rating The gross axle weight rating is the maximum distributed weight that may be supported by an axle of a road vehicle. Typically, GAWR is followed by either the letters FR or RR, which indicate front or rear axles respectively.-Importance:... |
lb/axle | kg/axle | durability, economics | larger is better for vehicles carrying loads | Ultimately limited by the hardness of the road surface and legal limits intended to limit damage to it |