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SECTION I--SUMMARY and low-speed designs, with the definition being low-speed roads with speed limits of 40 mph or less (5 mph less than the highest AASHTO design speed) and high-speed roads with speed limits of 45 mph or greater (5 mph less than the lowest AASHTO design speed). Grouping of strategies by speed range is done for convenience and focus. Users of this guide need not be constrained, however, by the definitions and groupings. A user may find that a strategy discussed in the low-speed guide may have application and value in a nominally high-speed condition. This is not only acceptable but considered good use of the guide. The strategies discussed are shown in Exhibit I-1. General Description of the Problem Excessive or inappropriate speeds result from two basic problems, both of which involve human factors considerations. Driver behavior (i.e., consciously choosing a clearly inappropriate speed) is one aspect of the problem. The second is associated with driver response to the environment (i.e., inadvertent selection of a speed that is inappropriate or unsafe, failure to adjust or change speeds, or failure to perceive the speed environment and as a result incur risk of a collision or conflict). It is both of these types of problems that this guide seeks to address. Approximately 42,000 automobile-related fatalities occur each year in the United States, and historically, nearly one-third of fatal crashes involve speeding, as shown in Exhibit III-1. In Traffic Safety Facts 2006--Speeding, the National Highway Transportation Safety Administration (NHTSA) defines a speeding-related crash as a crash in which "the driver was charged with a speeding-related offense or if an officer indicated that racing, driving too fast for conditions, or exceeding the posted speed limit was a contributing factor in the crash" (NHTSA, 2006). This section details characteristics of speeding-related fatalities and fatal crashes obtained from a review of recent literature and the NHTSA Fatality Analysis Recording System (FARS) database. In 2006, there were 42,708 traffic fatalities, 30 percent (13,113) of which involved speeding. Of these fatalities, 13,543 (32%) occurred as a result of a speeding-related crash. Only 13% of all speeding-related traffic fatalities occurred on Interstate roadways, while 72% occurred on non-Interstate roads. Of the crashes on non-Interstate roads, 29% occurred on low-speed non-Interstate roads (defined for the purpose of this report as roads with a speed limit of 40 mph or less), and 43% occurred on high-speed non-Interstate roads (roads with a speed limit of 45 mph or more). Roadways with unknown or no statutory speed limits accounted for 15 percent of speeding-related fatalities. These data are taken from Traffic Safety Facts 2006Speeding (NHTSA, 2006). A further review of 2005 FARS data yields additional insights into fatal crash characteristics (NHTSA, 2005): ˇ Approximately 39 percent of speeding-related fatal crashes occurred on horizontal curves. ˇ Speeding-related fatalities occur primarily in single-vehicle crashes; 70 percent of speeding-related fatalities on low-speed roads, and 67 percent on high-speed roads occurred in this manner of collision. ˇ 38 percent of speeding drivers in a fatal crash were under the age of 25. ˇ 40 percent of drivers that were speeding in fatal collisions had a blood alcohol content (BAC) of at least 0.08. I-2