Editing Vehicle (section)

=== Friction ===
All or almost all of the useful energy produced by the engine is usually dissipated as friction; so minimizing frictional losses is very important in many vehicles. The main sources of friction are [[rolling friction]] and [[drag (physics)|fluid drag]] (air drag or water drag).

Wheels have low bearing friction, and pneumatic tires give low rolling friction. Steel wheels on steel tracks are lower still.<ref>{{cite web|last=Nice |first=Karim |url=http://auto.howstuffworks.com/tire4.htm |title=HowStuffWorks – How Tires Work |publisher=Auto.howstuffworks.com |date=19 September 2000 |access-date=8 January 2013}}</ref>

[[Aerodynamic drag]] can be reduced by streamlined design features.

Friction is desirable and important in supplying [[traction (engineering)|traction]] to facilitate motion on land. Most land vehicles rely on friction for accelerating, decelerating and changing direction. Sudden reductions in traction can cause loss of control and accidents.