March 10, 2008 - Conscious of tougher fuel-efficiency standards, Lamborghini and Hummer are trying get in on the environmental act. The sportscar maker and the military muscle-car manufacturer both unveiled green concept vehicles at the Geneva Auto Show last week, Reuters reports.

Hummer's new HX runs on cleaner-burning ethanol instead of gas, while Lamborghini's latest iteration of its Gallardo model weighs slightly less than previous versions for a modest reduction in greenhouse gas emissions.

While it's unclear whether or how these new models might compete with their much smaller, more fuel-efficient counterparts, it's significant that the sports/muscle car makers (including Land Rover) - traditionally considered outside the green debate due to their overarching focus on power and performance - are making strides in a greener direction. Concern over tightening government regulation is a likely cause, with taxes on big vehicles in France, government websites with information and green rankings in the U.S. and in the U.K., and even an EU-wide mandate in the works to force a "health warning" in all car ads.