signs returned 5 min after the rumble strip hit. Essentially no effects were seen due to type of strip." A 2003 Montana study suggested that on Interstates, shoulder rumble reduced the roll-over accident rates but the severity of unprevented roll-over accidents increased. This was thought to be due to the rumble strip "scaring" sleeping drivers to the extent that they overreacted. This problem was more pronounced on primary highways (that have narrower shoulders) with rumble strips. "Classic" one-car crashes The 'classic' one-car crash results when a vehicle slowly drifts to the right, hits dirt or rumble strips on the right shoulder of the road, and the driver becomes alert and overreacts, jerking the wheel left to bring the vehicle back onto the road. This motion causes the left front tire to strike the raised edge of the pavement at a sharp angle, often causing a rollover or a swerve into oncoming traffic. This form of one-car crash is "classic" because it occurs very often. Raised edges of pavement (or "edge-drops") were once common, but are now recognized as a hazard; it is now standard practice to level the gravel shoulder with the pavement, although edge-drops may reform due to soil erosion. This "slowly drift to the right" scenario applies to jurisdictions with right-hand traffic, so in jurisdictions with left-hand traffic it would be a "slowly drift to the left" scenario. This phenomenon implies that a sleeping driver often does not react and begin to recover, until all four wheels have struck a rumble strip; if the paved shoulder is narrower than the width of the vehicle wheel track, a rumble strip may not prevent a sleeping driver from going off the road. On a single-lane highway, an overreacting driver has less room to regain control, which may exacerbate their initial overreaction after striking the strips, resulting in a roll-over or head-on collision. A crash investigating officer stated: "It's consistent with someone who falls asleep or overreacts to the rumble strips", which implied that this was not the first time the officer has witnessed this situation. Note that in the KATU.com article photograph (in the upper left-hand corner) of the crash scene, the passenger-side tire print in the soft shoulder that suggests that all four wheels passed over the rumble strip before the driver attempted the unsuccessful recovery. Fluidity of accident profiles Accident profiles can change over time, and this can