Drafting or Tailgating is a very useful racing tactic. The Driving Skill can be performed by driving very close to the rear of an opposing rival's vehicle at high speed. This will earn players a slight speed boost and additional boost.
Drafting can also be used to set up a Takedown. By lining up behind a rival in front of a player it can be shunted and cause the rival to lose control. Another tactic is that a player can swing left and right while tailgating without touching a rival to score a Psyche Out Takedown.
The additional speed acquired when tailgating comes from the fact that air occupies space, and any moving body collides with it at all times; air creates resistance against the moving body and slows it down, which is more noticeable on bodies that move with high velocities and have comparatively large surfaces, such as cars.
As the body moves, it pushes air off, leaving vacuum behind, which is quickly filled with more air. This is, essentially, like cutting through butter with a knife, for instance, hence the expression "cutting the air". As (or even before) this vacuum is filled with air again, another moving body (the tailgating car) passes through it; as the air particles are either moving in or simply not there, the car suffers significantly less air resistance, and it is able to move faster.