Ground pressure
Encyclopedia
Ground pressure is the pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

exerted on the ground by the tires or tracks
Caterpillar track
Continuous tracks or caterpillar tracks are a system of vehicle propulsion in which modular metal plates linked into a continuous band are driven by two or more wheels...

of a motorized vehicle, and is one measure of its potential mobility, especially over soft ground. Ground pressure is measured in pascals (Pa) which corresponds to the EES
United States customary units
United States customary units are a system of measurements commonly used in the United States. Many U.S. units are virtually identical to their imperial counterparts, but the U.S. customary system developed from English units used in the British Empire before the system of imperial units was...

unit of pounds per square inch
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...

(psi). Average ground pressure can be calculated using the standard formula for average pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

: P = F/A. In an idealized case, i.e. a static
Static
Static has several meanings:* Static electricity, a net charge of an object** The triboelectric effect, e.g. from shoes rubbing carpet* White noise, a random signal with a flat power spectral density** Noise , a type of radio interference...

, uniform net force normal
Surface normal
A surface normal, or simply normal, to a flat surface is a vector that is perpendicular to that surface. A normal to a non-flat surface at a point P on the surface is a vector perpendicular to the tangent plane to that surface at P. The word "normal" is also used as an adjective: a line normal to a...

to level ground at Earth sea level, this is simply the object's 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:...

divided by contact area. The ground pressure of motorized vehicles is often compared to the ground pressure of a human foot
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...

, which can be 60 - 80 kPa while walking or as much as 13 MPa for a person in spike heels.

Increasing the size of the contact area on the ground (the footprint) in relation to the weight decreases the ground pressure. Ground pressure of 14 kPa (2 psi) or less is recommended for fragile ecosystems like marshes. Decreasing the ground pressure increases the flotation, allowing easier passage of the body over soft terrain. This is often observed in activities like snowshoe
Snowshoe
A snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation"....

ing.

## Example Ground Pressures

All examples are approximate, and will vary based on conditions

Hovercraft: 0.7 kPa (0.1 psi)

Human on Snowshoe
Snowshoe
A snowshoe is footwear for walking over the snow. Snowshoes work by distributing the weight of the person over a larger area so that the person's foot does not sink completely into the snow, a quality called "flotation"....

s: 3.5 kPa (0.5 psi)

Rubber-tracked ATV
All-terrain vehicle
An all-terrain vehicle , also known as a quad, quad bike, three wheeler, or four wheeler, is defined by the American National Standards Institute as a vehicle that travels on low pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control...

: 5.165 kPa (0.75 psi)

Diedrich D-50 - T2 Drilling rig: 26.2 kPa (3.8 psi)

Human
Human
Humans are the only living species in the Homo genus...

male (1.8 meter tall, medium build): 55 kPa (8 psi)

M1 Abrams
M1 Abrams
The M1 Abrams is a third-generation main battle tank produced in the United States. It is named after General Creighton Abrams, former Army Chief of Staff and Commander of US military forces in Vietnam from 1968 to 1972. The M1 is a well armed, heavily armored, and highly mobile tank designed for...

tank: 103 kPa (15 psi)

1993 Toyota 4Runner
Toyota 4Runner
The Toyota 4Runner is a mid-size SUV manufactured by Toyota and sold throughout the world from 1984 to the present. In Japan it was known as the Toyota Hilux Surf...

/ Hilux Surf: 170 kPa (25 psi)

Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

(550 kg, 1250 lb
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

): 170 kPa (25 psi)

Passenger car: 205 kPa (30 psi)

Wheeled ATV: 240 kPa (35 psi)

Mountain bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

: 245 kPa (40 psi)

Racing bicycle: 620 kPa (90 psi)

Note:
Pressures for Man and Horse are for standing still. A walking human will exert more than double his standing pressure. A galloping horse will exert up to 3.5 MPa (500 psi). The ground pressure for a pneumatic tire is roughly equal to its inflation pressure.