done completely "pure", due to Troop T concurrently conducting a campaign to reduce drunk driving and increase seat-belt use, and Troop T's campaign would also reduce the number of fatal vehicle crashes. 10 to 24 percent of crashes are estimated to involve fatigue or inattention of some kind, but these numbers are based on guesswork. Despite this, the New York State Thruway study indicating a 65% to 70% reduction continues to be cited in literature. New Zealand used rumble strips in small applications since the late 1980s, and started a larger program in 2004. Research in the country indicated that lane delineation with rumble strips reduced crashes by an average of 27% over all crash types and studies, with types of crashes such as "run off road" being reduced by up to 80% in some studies. Centre-line rumble strips showed similar effects. However, it appears that there were other crash reduction initiatives that may have contributed to the relatively sizable results. The effects remained even after road users had become accustomed to the feature, while other road safety measures (when studied at specific installations) often showed declining effectiveness over time. Cost-benefit analysis showed that even on relatively low-volume roads, the costs of applying the markings were quickly exceeded several-fold by the economic benefits of improved road safety (as counted by the reduction of crash rates weighted against the average social costs of a crash). Further research in New Zealand led to recommendations that strip edge lines and centre lines be marked over extended lengths of road, rather than just at focal points and crash black spots. Apart from the safety benefits of providing a consistent road environment, continuous markings provide valuable alerts to drivers long before the more common crash spots. A one-third reduction rate is commonly cited and is based on an average of early studies. It includes the New York State Thruway and Pennsylvania Turnpike results which produced a skewed result non-representative of typical situations. The one-third reduction rate and the Pennsylvania Turnpike Study (with a 60% reduction) are the rule-of-thumb and the classic study, but these can be misleading as CSRS do not have a "fixed" effectiveness that may be applied to any highway. A 1999 FHWA study concluded that "a best guess" might be 20% to 30% reduction in single-vehicle run-off-road crashes on rural freeways, with less effective on urban freeways. Almost all before-and-after studies are