<P> Transverse rumble strips (TRS) may be used to warn drivers: of the need to stop (e.g. intersections, toll plazas); the need to slow down; the need to change lanes; of a change in roadway alignment; that they are leaving the traveled way; upcoming construction zones; wildlife crossings; and other potentially unexpected conditions . </P> <P> As a speed reduction measure, TRS have been marginally successful . A 2003 Texas study concluded: "However, the actual reductions in speeds have been in the range of 2 to 8 mph (3 to 13 km / h), which may be barely perceptible to the traveling public . There have been no studies that evaluate the reduction of excessive speeds ." </P> <P> As a construction zone safety measure, the effectiveness appears unclear . A 2007 Minnesota study concluded that while transverse rumble strips offer a low cost and easy - to - install option, they "did not seem to be successful at reducing approach speeds at the project sites". A 2005 Maryland study stated: "In conclusion, although in the present study rumble strips did not produce the desired speed reduction effect, its use for work zone applications is still highly encouraged; though, not as a speed control measure but as a driver's attention - catching device ." </P> <P> As an approach stop - control crash reduction measure they have proven successful . The 2003 Texas indicated: "The majority of studies found reported large reductions (40% to 100%) of accidents after installing transverse rumble strips ." </P>

Who invented the bumps on the side of the road