Here's some relevant info from the internet.
Cars
Automobiles began using air brakes as early as 1903. The first car to have them was called a Tincher. As improvements continued to be made to car air brakes, a vacuum power booster braking system was developed that is similar to modern air brakes. It used a vacuum to reduce the physical strength need to apply the brakes. This system was first used on the 1928 Pierce-Arrow.
Competition
Besides Westinghouse, other companies began to develop air brake systems. One of these, Bendix, eventually mergeed with Westinghouse Automotive Air Brake Company in 1930. By 1934, the company had taken the air braking system worldwide and opened plants in France, Germany, Ital and England.
WWII
The outbreak of World War II accelerated improvements and refinements of the air braking system. By 1949, air brakes were standard on heavy trucks, tractor-trailers and buses. Other companies also continued to enter into the market and not only develop air brakes, but newer versions of braking systems.
Read more: History of Air Brakes | eHow http://www.ehow.com/about_6393312_history-air-brakes.html#ixzz2V4htYxyh