Exposed Physical Structure

This example of the air brake consists of a physical structure on the exterior of a vehicle that will increase the vehicle's drag coefficient, and therefore slow it down. Air brakes of this sort are ineffective at normal road vehicle speeds, and therefore are reserved for vehicles which need to quickly decelerate from high speeds, such as race and high performance sports cars.

Many high performance sports and racing cars utilize air brakes in order to slow the cars down from high speeds. The Bugatti Veyron, one of the fastest production cars in the world,  features a rear spoiler which, at speeds above 200 km/h (120 mph), also acts as an air brake, snapping to a 55° angle in 0.4 seconds once the brake pedal is pressed, providing an additional 0.68 g (6.66 m/s2) of deceleration (equivalent to the stopping power of an ordinary hatchback).Top Fuel Dragsters and other drag racing cars that routinely reach speeds greater than 150 miles per hour use a physical air brake via a parachute(s) after the completion of a race.

In 1994, NASCAR introduced roof flaps to the cars, which are designed to keep cars from becoming airborne and possibly flipping. Following Rusty Wallace's crash at Talladega, Penske Racing designed the original roof flaps. NASCAR team owner Jack Roush helped improve on the design of the roof flaps, in conjunction with Embry-Riddle Aeronautical University, Daytona, Florida, USA. During a spin, the car rotates it eventually reaches an angle where the oncoming air reacts with the profile of the vehicle in the same manner as a wing. If the speed is high enough, air flowing over this aerofoil shape will create sufficient lift to force the car to become airborne. To prevent this, NASCAR developed a set of flaps that are recessed into pockets on the roof of the car. As a car is turned around and reaches an angle where significant lift occurs, the low pressure above the flaps causes them to deploy. The first flap, oriented 140 degrees from the centerline of the car, typically deploys first. After flap deployment, higher pressure air is forced through an air tube which connects to a second flap, deploying it. This second flap ensures that, should the car continue to spin, no further lift will be created as the vehicle's angle changes. The deployment of these flaps eliminates most of the lift on the vehicle. The roof flaps generally keep the cars on the ground as they spin, although it is not guaranteed.