Slipstream

The slipstream of a moving object is a region of reduced pressure or even suction (negative pressure), exerted in the neighbourhood of the object and in the direction of its movement, and caused by its movement through a medium.

The term "slipstreaming" is most often used in relation to objects moving through air, though not necessarily flying. If a following object, moving at the same speed, can position itself within the slipstream, it will require less energy to maintain its speed than if it was moving independently, because the front object blocks a significant amount of air resistance. Using this principle is called slipstreaming.

Slipstreaming is important in a number of contexts, including:

• Cycling: in fast bicycle races, competitors attempt to 'draft' or use one another's slipstream, breaking to overtake the leader only at the last possible moment. In cycle touring, on the other hand, members of a group can take turns at the leading position, enabling one another to rest a little.