There are a broad range of metrics that denote the relative capabilities of various vehicles. Most of them apply to all vehicles while others are type-specific.
| Measurement |
Imperial unit |
Metric unit |
Affects |
General preference |
Notes |
| 0 to 60 mph |
seconds |
seconds |
acceleration |
lower is better |
|
| 0 to 100 to 0 mph |
seconds |
seconds |
acceleration & braking |
lower is better |
formerly common in British publications |
| Braking distance |
feet |
meters |
safety |
shorter is better |
|
| Brake specific fuel consumption |
lb/hp h |
g/kWh |
economics |
lower is better |
|
| Drag coefficient |
(ratio) |
(ratio) |
economics, top speed |
lower is better |
|
| Frontal cross-section area |
ft2 |
m2 |
economics, top speed |
lower is better |
if area is too small, vehicle becomes difficult to use |
| Fuel economy |
mpg |
l/100 km |
economics |
greater is better (mpg), lower is better (L/100 km) |
must be specified on new vehicles for sale in the US |
| Maximum g-force(s) |
'g' |
'g' |
acceleration |
higher is usually better |
measures cornering, braking or forward acceleration |
| Ground pressure |
psi |
Pascal |
traction |
lower is better in soft ground, reduces bogging; higher with loose surface |
has greater impact on off-road vehicles |
| Lift to drag ratio |
- |
- |
economics |
higher is better for aircraft |
improved by narrow, long wings |
| Power-to-weight ratio |
hp/lb |
W/kg |
acceleration |
higher is better |
|
| Polar moment |
lbft2 |
kgm2 |
handling |
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 |
| 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 |
lower is better (for any given speed) |
in airbreathing jet engines it is improved by using more inert air for propulsion (i.e. lower exhaust velocity), in rockets, higher exhaust velocity |
| Specific fuel consumption (shaft engine) |
lb/hp h |
kg/kW h |
economics |
lower is better |
for shaft engines less fuel use for a given output power means higher efficiency |
| specific impulse |
seconds |
seconds or kN s/kg |
economics |
higher is typically better |
in airbreathing jet engines it is improved by using more inert air for propulsion (i.e. lower exhaust velocity), in rockets, higher exhaust velocity |
| Top speed |
mph |
km/h |
Maximum rate of straight line travel |
higher is better |
Electronically limited in some cars for safety (mostly due to concerns of high speed tire failure) |
| Weight |
lb |
kg |
acceleration, braking distance |
lower is better |
|
| Weight distribution |
% |
% |
handling, acceleration, traction |
close to 50:50 is commonly considered better |
|
