Safety Evaluation of Permanent Raised Pavement Markers (2004) / Chapter Skim
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From page 24... ...
States that implement recessed markers either could identify only very small samples of roadways with this marker type or have discontinued their implementation in recent years. California and Texas were the only two states that implement the conventional marker type on a wide scale; however, no recent PRPM installations took place, and a suitable sample for a before-and-after safety evaluation was not available.
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The reference and comparison group location data were required for developing safety performance functions to control for changes in safety at treatment locations that are due to factors other than PRPM installation (e.g., changes in traffic volume)
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, samples of untreated roadways of the relevant roadway types were identified to compose a reference group from which safety performance functions (SPFs) or crash prediction models were calibrated for each year of the analysis period.
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To address this constraint and to account for time trends in more recent years (i.e., 1998–2000) , the research team collected additional data for urban Interstate highways in Madison County, Wisconsin.
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3.2.5 Traffic Volume Data The variables required at treatment sites, reference group sites, and comparison group sites were • AADT volumes, • Percentage of annual average nighttime traffic volumes, and • Percentage of heavy vehicles. Crash Type Definition Total All crashes reported and entered in the database Fatal and injury Crashes that resulted in fatal or nonfatal injuries Daytime Crashes that occurred between sunrise and sunset Nighttime Crashes that occurred between sunset and sunrise Dry Crashes that occurred on "road surface condition" reported as "dry" Wet Crashes that occurred on "road surface condition" reported as snow, wet, ice, or any other nondry conditions Wet-nighttime Crashes that occurred "road surface condition" reported as snow, wet, ice, or any other nondry conditions between sunset and sunrise Guidance-related Crashes with reported "impact type" as run-off-road, head-on, and sideswipe for fatal, injury, and property-damage-only combined Head-on Crashes with reported "impact type" as head-on for fatal, injury, and property-damage-only combined TABLE 3-8 Crash type definitions (text continued p.
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Illinois 5.0 30.2 54.3 10.6 8.0 22.0 11.6 New Jersey 44.0 6.5 46.6 2.8 10.0 25.0 11.2 New York 2.4 22.8 72.2 2.6 10.0 25.0 11.8 Pennsylvania 13.7 32.3 45.6 8.4 8.0 32.0 11.8 TABLE 3-11 Summary information: lane widths at two-lane treatment sites TABLE 3-10 Roadway data files and their sources
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Missouri 0.1 98.7 1.2 11.0 18.0 12.0 New York 0.5 98.7 0.8 9.0 17.0 12.0 Pennsylvania 1.9 94.2 3.5 10.0 25.5 12.2 Wisconsin 0.0 99.7 0.3 12.0 18.0 12.0 TABLE 3-15 Summary information: shoulder widths at four-lane freeway treatment sites State % of total roadway length when shoulder width ≤ 4 ft % of total roadway length when shoulder width > 4 ft and ≤ 6 ft % of total roadway length when shoulder width > 6 ft and ≤ 8 ft % of total roadway length when shoulder width > 8 ft and ≤ 10 ft % of total roadway length when shoulder width > 10 ft Minimum shoulder width (ft) Maximum shoulder width (ft)
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Tables 3-25 and 3-26 show the percentage of treatment site length with and without shoulder rumble strips for freeways and expressways, respectively. State % of total roadway length (urban)
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% of total roadway length (rural) Pennsylvania 18.6 81.4 Wisconsin 11.6 88.4 TABLE 3-19 Summary information: environment type at four-lane expressway treatment sites State Information Received Source Illinois AADTs for 1991, 1992, 1994, and 1997 to 2000 Highway Safety Information System (HSIS)
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