Should there be a 75 mph speed limit on the Autobahn to reduce CO2 emissions?

Modern cars are at their most fuel-efficient at 55 mph, and American politicians have used this speed limit to encourage fuel conservation in the past. But how do things look on the German Autobahn, the most famous stretch of public high speed road in the world?
Writing at The Truth About Cars, Robert Farago discusses the "gentleman's agreement" that for years kept most German cars' top speed at 155 mph. But, thanks to clean technologies throughout the German car industry, Farago says, "the tailpipe emissions produced by Germany's increasingly modern automotive fleet are virtually sterile." and the Autobahn only makes up a small percentage of Germany's roads.

Nonetheless, German environmentalists are now showing greater concern for CO2 emissions on the Autobahn. At the end of December, Andreas Troge. the President of Germany's Federal Environmental Agency (UBA) and a long time auto industry critic, called for a 75mph speed limit on all German Autobahn stretches. Troge said this will reduce Germany's CO2 emissions by 30 percent. Germany Transport Minister Wolfgang Tiefensee didn't seem enthused by the idea, saying, "a general speed limit on open stretches of road does not make sense."

[Source: The Truth About Cars]