Safety
The danger of exploding tanks has been solved with the introduction of filament wound composite tanks which are DOT certified and have been used for storing liquefied natural gas in fleet trucks and cars for over 10 years. Unlike aluminum scuba tanks, composite tanks 'soft fail', which means they crack on severe impact and leak rather than explode. Work is also being done to make tanks that conform to the floor of a vehicle. Such a tank could be placed under the vehicle with high volumetric efficiency and extending the range of the vehicle.
Research
Every year, more advances are made with compressed air vehicles. Studies have been conducted by universities and the Department of Energy that demonstrate the cost effectiveness and practicality of compressed air technology. Currently, it appears that Europe is leading the world in producing air technology that began in the United States in the 1800's. Mr. Hampton, Co-founder of HUE, is committed to helping America regain its world leadership position in technological advances through HUE Compressed Air Technology.
The following links have supporting information:
Air Hybrid Vehicle Study at UCLA Engineering School
Compressed Air - System Overview
BBC News | AFRICA | The car that runs on air
News in Science - Green buggy runs on hot air - 25/08/2004
CNN.com - Car that runs on compressed air - Mar 30, 2005