The purpose of an air bag is to slow the passengers’ speed to zero with little or no damage. The air bag has the space between the passenger and the steering wheel or dash board and a fraction of a second to work. Even that tiny amount of space and time is valuable if the system can slow the passenger smoothly rather than forcing an abrupt halt to his/her motion.
The air bag itself is made of thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door. The crash sensor is the device that tells the bag to inflate.* Inflation happens when there is a collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 km per hour).
A mechanical switch is flipped when there is a mass shift that closes an electrical contact, telling the sensors that a crash has occurred. The sensors receive information from an accelerometer built into a microchip. Since the power-steering pump on most cars today runs constantly, pumping fluid all the time, it wastes horsepower. This wasted power translates into wasted fuel. You can expect to see several innovations that will improve fuel economy.
One of the coolest ideas on the drawing board is the “steer-by-wire” or “drive-by-wire” system. These systems would completely eliminate the mechanical connection between the steering wheel and the steering, replacing it with a purely electronic control system. Essentially, the steering wheel would work like the one you can buy for your home computer to play games.
It would contain sensors that tell the car what the driver is doing with the wheel, and have some motors in it to provide the driver with feedback on what the car is doing. The output of these sensors would be used to control a motorized steering system. This would free up space in the engine compartment by eliminating the steering shaft. It would also reduce vibration inside the car.