Britain's Automobile Association has found another bump in the road to environmental kindness: speed bumps and really low speed limits. They took a car that got 58-mpg running a constant 30-MPH, and ran it over speedbumps at the Millbrook Proving Ground, slowing down and speeding up for each bump. What they discovered was that mileage dropped to 31-mpg and carbon dioxide emissions went up. The findings correlate with those of the country's Transport Research Laboratory, which reported that…