GreenMan Technologies said its American Power Group subsidiary has gotten government approval for a clean alternative-fuel vehicle and engine conversion program involving the 2004 Caterpillar C-15 engine family.

The Environmental Protection Agency approved APG's submission for an Outside Useful Life (OUL) Heavy Duty program. It uses APG's latest V5000 Dual Fuel Turbocharged Natural Gas design. This first OUL Heavy Duty Diesel EPA approval provides APG a path for additional submissions of conversion programs for an array of heavy-duty aftermarket diesel truck engines, said the company.

Power Systems Research, a supplier of business information, estimates that approximately 4.6 million medium- and heavy-duty diesel vehicles, 96% of those in service, fit into either the Inside or Outside Useful Service classifications.

"Based on our research, we believe we have identified the top 40 heavy duty engine families operating on the U.S. roads today, representing nearly 400,000 vehicles and an identified market potential in excess of $3.9 billion," said Lyle Jensen, president and CEO of GreenMan.