Blue City Highway had always been notorious for its tight curves and poor roadway visibility, and the accident rate there was generally very high. Last year the highway was redesigned to broaden the curves and improve roadway visibility. Drivers report that they now feel much safer driving on the highway and that the redesign has been a big improvement. But the number of accidents on the highway has not been significantly lower in the six months since the redesign than it was in the six months before the redesign. Therefore, the redesign clearly did not improve the curves and roadway visibility enough to make a difference.