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From page 3... ... 3 Literature Review The following literature review summarizes the impetus for improving median barrier guidance, the history of median barrier guidance through 2015, and the evolution of crash testing specifications for median barriers. Recent additions to the literature on the placement of median barriers are also included. Read the entire page →
From page 4... ... 4 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers Figure 1. Crash scene diagram: U.S. Read the entire page →
From page 5... ... Literature Review 5 Crash location U.S. Route 41 near Slinger, Wisconsin Interstate 65 near Munfordville, Kentucky Interstate 5 in Orland, California Statewide fatal accidents • 0.6% of total head-on collisions with median barriers • 1.9% of total without median barriers • 1.74 per 100 million vehicle miles traveled (2008) Read the entire page →
From page 6... ... 6 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers cross-median accidents, including changes in the vehicle fleet and the percentage of heavy trucks using the roadways. Read the entire page →
From page 7... ... Literature Review 7 Work with the Federal Highway Administration to identify cross-median crash rates that call for special consideration when selecting median barriers, and publish the rates in the Roadside Design Guide. Read the entire page →
From page 8... ... 8 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers Figure 3. Crash scene diagram: Interstate 5 in Orland, California. Read the entire page →
From page 9... ... Literature Review 9 barriers were not warranted at this location, noting ". Read the entire page →
From page 10... ... 10 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers barriers. (Michie 1971) Read the entire page →
From page 11... ... Literature Review 11 openings] , accident history, alignment, sight distance, design speed, traffic volume, and median width should be made prior to non-freeway installations." (AASHTO 1974) Read the entire page →
From page 12... ... 12 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers that the warrant was for freeways and expressways rather than "high-speed, controlled access roadways." (AASHTO 1977; AASHTO 1989a) It was also stated that the guidance was "relatively subjective and does not specifically address the cost-effectiveness issue." It was further noted that guidelines that account for speed, median, slope, vehicle mix, and ADT were under development. Read the entire page →
From page 13... ... Literature Review 13 The 2002 RDG referenced an ongoing study on median barrier warrants, indicating that changes to the warrant would be forthcoming. Read the entire page →
From page 14... ... 14 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers The current guidance (i.e., issued in 2006 and reiterated in 2011) for the use of median barriers is shown in Figure 8. Read the entire page →
From page 15... ... Literature Review 15 factors include: high percentages of heavy vehicles, horizontal curvature, or severe consequence of penetration. Many states adopted the recommendations of the RDG and have incorporated them into their standards. Read the entire page →
From page 16... ... 16 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers from the opposite direction." (Caltrans 2012) Either a collision or volume/width study warrant is suggested to identify locations for study (i.e., this is not a barrier installation warrant but a study warrant) Read the entire page →
From page 17... ... Literature Review 17 Figure 9. Caltrans freeway median barrier study warrant. Read the entire page →
From page 18... ... 18 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers was aware of the pending 2006 revisions of the RDG. The purpose of the guidelines was to provide ". Read the entire page →
From page 19... ... Literature Review 19 3.2.2.7 South Dakota. Chapter 10 of the South Dakota Road Design Manual recommends a study to determine whether median barriers are warranted when the criteria shown in Figure 12 are met. Read the entire page →
From page 20... ... 20 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers Figure 11. New Jersey warrants for median barrier for freeways and expressways. Read the entire page →
From page 21... ... Literature Review 21 Figure 12. South Dakota median barrier study warrant. Read the entire page →
From page 22... ... 22 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers • Traffic volumes, including estimated traffic growth and percentage of trucks; • Types and severity of crashes; • Posted speed limit; • Type of facility, including controlled-access or non-controlled-access with crossovers; • Roadway alignment; • Ramp locations; and • Elimination of barrier gaps. 3.2.2.9 Washington. Read the entire page →
From page 23... ... Literature Review 23 Figure 15. 2001 WSDOT median barrier warrants. Read the entire page →
From page 24... ... 24 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers 3.3 Crash Testing Specifications for Median Barriers NCHRP Report 153: Recommended Procedures for Vehicle Crash Testing of Highway Appurtenances (Bronstad 1974) was published in 1974 to provide uniform barrier testing procedures and criteria. Read the entire page →
From page 25... ... Literature Review 25 TL1 TL2 TL3 TL4 TL5 TL6 NCHRP Report 350 (Ross 1993) Small Car 820C 31 mph/20° 44 mph/20° 62 mph/20° Small Car 700C Pickup 2000P 31 mph/25° 44 mph/25° 62 mph/25° SUT 8000S 50 mph/15° Tractor Van-Trailer 36000V 50 mph/15° Tractor TankTrailer 36000T 50 mph/15° MASH Small Car 1100C 31 mph/25° 44 mph/25° 62 mph/25° Pickup Truck 2270P 31 mph/25° 44 mph/25° 62 mph/25° SUT 10000S 56 mph/15° Tractor Van-Trailer 36000V 50 mph/15° Tractor TankTrailer 36000T 50 mph/15° NOTE: Content in bold-italic font highlights changes from NCHRP Report 350 to MASH. Read the entire page →
From page 26... ... 26 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers A series of placement schematics were included in NCHRP Report 711 showing shaded areas that should be avoided. The symmetric V-shaped median placement schematics are shown in Figure 17; however, Figure 18 should be used if the slopes of the median exceed 6H:1V. Read the entire page →
From page 27... ... Literature Review 27 coordination with the NCHRP Project 22-22(02) research team provided the preliminary limits for placement. Read the entire page →
From page 28... ... 28 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers The 1977 Barrier Guide presented a hand-calculation encroachment-based method based on work by Glennon. Read the entire page →
From page 29... ... Literature Review 29 encroachment speed and angle. The probability distribution was calculated using data collected by Cooper in Canada during the late 1970s (i.e., the Cooper data) Read the entire page →
From page 30... ... 30 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers by definition, must include multiple vehicles. Recall the cross-median crash definition provided in Section 2. Read the entire page →
From page 31... ... Literature Review 31 opposing lanes as compared with the total number that cross the median. Ideally, the four-lane non-freeway model could be used to develop an encroachment adjustment factor for RSAPv3 because this model most closely resembles the base conditions of the encroachment probability model. Read the entire page →
From page 32... ... 32 Selection and Placement Guidelines for Test Level 2 Through Test Level 5 Median Barriers effort also developed encroachment adjustment factors for both curves and grades to be used in the encroachment probability model to represent the influence of the variety of horizontal curves or vertical grades on encroachment frequency. These models can be used to represent how many vehicles enter the median and subsequently have a crash on divided roadways and how many vehicles cross the centerline of an undivided roadway and crash on the opposite edge of the roadway. Read the entire page →

From page 3...

... 3 Literature Review The following literature review summarizes the impetus for improving median barrier guidance, the history of median barrier guidance through 2015, and the evolution of crash testing specifications for median barriers. Recent additions to the literature on the placement of median barriers are also included.