The Senate passed its own version of this House bill in June 2007. A month later, it returned to the House for conference in order to reconcile the two versions of the bill for Presidential review.

The bill’s future is uncertain, given that the Republican Party has characteristically shown strong support for Detroit by giving automakers extensive leeway in implementing reforms. Auto-emissions legislation varies on numbers and implementation dates, and many bills contain provisions that allow automakers to disregard fuel economy hikes if such moves are not cost-effective for the company.

H.R. 6 mandates a 35-mpg combined-fleet (both cars and light trucks) average fuel economy regardless of cost.