The impact of clean diesel vehicle companies being rewarded with tax credits in the US would be to stall the most promising technologies in fuel efficiency. This causes our country to be more dependent on the foreign oil. Which is the opposite of why congress even created the clean vehicle tax credits.
The impact that hybrid vehicles would have is not even fully tapped into yet. French researchers said, "Hybrid electric vehicles (HEVs) that run on both gasoline and stored electricity should be no more than a stop gap until more sustainable technology is developed" (cleantech.com). This means that there is a possibility of having cars in the future that aren't dependent on gas at all through the technology that is yet to be explored by perfecting the hybrid vehicle.
