**FILE** President Obama signs a presidential memorandum outlining the next steps for cleaner and more efficient vehicles on May 21, 2010, in the Rose Garden of the White House in Washington. From left: Transportation Secretary Ray LaHood, White House energy czar Carol Browner, EPA Administrator Lisa Jackson, Navistar Chief Executive Officer Daniel Ustian, Waste Management driver Anthony Dunkley and Daimler Trucks North America Chief Executive Officer Martin Daum. (Associated Press)
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