India, Oct. 28 -- We trust road signs to keep us safe. Flashing signs, road markers, and street lights all try to keep drivers alert. But what if the road itself needs fixing? That was the question at a downhill intersection in Bellevue, Washington. A case study from the Federal Highway Administration (FHWA) revealed that the city tried several common fixes, to no avail. So, it changed the pavement in October 2004. Crashes at the intersection declined 78%, and costs related to crashes declined 83%. The story shows how important a road surface can be when drivers have to stop on a slope, and it has a few limits worth knowing.

The trouble spot was an intersection where drivers came downhill. The agency notes intersections have built-in cha...