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7 In the first volume (and subsequent volumes) of NCHRP treatments that balance the demands of agencies, stakeholders, Report 500, prospective engineering countermeasures and and users on these roadways. While highways, freeways, and their associated effectiveness are classified as "Tried," "Exper- other high-speed, limited-access roadways may have impor- imental," or "Proven" (3, pp. V-2 through V-3). This classi- tant roadside safety issues, the design of such roadways is out- fication permits readers to understand the level of testing side the scope of this study. performed on a specific countermeasure perceived to be effective for a safety improvement program. Summarized Examining Roadside Safety versions of the definitions given in the first volume of the in Urban Environments NCHRP Report 500 series for "Tried," "Experimental," and "Proven" are given below (3, pp. V-2 through V-3): The majority of travel undertaken in the United States occurs on urban roadways. Of the 2.9 trillion miles of travel Tried (T)--Strategies that have been implemented at a in 2003, roughly 1.8 trillion--62 percent--occurred in urban number of locations but for which valid safety evaluations areas (4). Urban roadways experience higher levels of traffic have not been identified. As a result, these strategies should congestion, particularly during morning and evening peak be used with caution until information about their effec- periods, and are much more likely to incorporate multi- tiveness can be accumulated and they can be reclassified as modal travel, including transit, bicycling, and walking. Trip Proven strategies. characteristics differ as well. While rural roadways experience Experimental (E)--Strategies that appear sufficiently more freight and long-distance, inter-regional trips, most promising so that application and testing appear feasible urban travel is characterized by intra-regional travel, partic- for a small-scale evaluation. These strategies do not have ularly household-related travel, such as work or shopping any valid safety evaluations or large-scale applications and trips. Thus, it is not surprising that the nature of urban road- warrant pilot studies to help elevate them to the category side crashes may also differ from the nature of rural roadside of Proven strategies. crashes. Proven (P)--Strategies that have been used in more than When one compares fatal crash frequency in rural areas one location and for which properly designed evaluations with crashes in urban areas, it is clear that fatal rural roadway were conducted to show their level of effectiveness. A user crashes occur more often than fatal urban roadway crashes. can apply a proven strategy with some level of confidence, While on-roadway crashes are slightly more frequent in rural but is also aware of appropriate applications as a result of areas, off-roadway crashes, which include rollover as well as these previous studies. fixed-object crashes, are considerably more frequent in rural areas. In the categories of fixed-object and rollover crashes The roadside-object literature review included in this re- only, fatal crashes are still more frequent in rural environ- port focuses on proven safety strategies for urban roadside ments. Approximately 60 percent of fatal fixed-object crashes safety; however, Tried and Experimental strategies are also and 77 percent of fatal rollover crashes occurred in rural included in an effort to provide a comprehensive listing of environments. known or perceived applications. In addition, this chapter re- Although focusing solely on fatal crashes risks underesti- views the following: mating the likelihood of a roadside crash for urban areas, fatality crash information is dependably reported and does Roadside crash statistics, in an effort to identify the specific provide some indication regarding crash trends. Table 3 shows nature of roadside crashes in urban areas; fatal crash conditions for common roadway classes for urban The various strategies currently in use in urban environ- and rural environments. Fatal fixed-object crashes for the ments to keep vehicles from leaving the travelway; and roadway classes shown are more pronounced in rural areas. General information, safety research, and proposed safety Pedestrian and bicycle fatalities, on the other hand, are much strategies for a variety of potential roadside objects com- more of an urban problem. For the road classes under con- mon to the urban environment. sideration, fatal pedestrian crashes are almost twice as likely to occur in urban environments as in rural ones. Pedestrian Although this review targets the design of roadsides in urban and bicycle activity is more common in urban environments, areas, much of the literature on roadside design has been based and the increased presence of pedestrians and bicyclists in- on studies of rural environments. As a result, the literature on creases the possibility that such a crash will occur. rural roadside safety is included when it is applicable. In general, fatal crashes with most types of fixed objects Finally, this review focuses specifically on those roadways occur more often in rural environments than in urban ones classified as urban arterials, collectors, and local streets because (see Table 4). When one considers specific roadway classes, urban stakeholders are most vocal about wanting roadside however, several exceptions emerge, particularly on roadways