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Federal Highway Administration Department of Transportation Effective Lateral Placement of Cable Barriers in Flat-Bottom, Sloped Medians Dr. Dhafer Marzougui NCAC, George Washington University Ashburn, VA under contract to Offce of Safety R&D Turner Fairbank Highway Research Center Federal Highway Administration McLean, VA Slide 2 Federal Highway Administration Department of Transportation Introduction: Cross median crashes have grown to be a serious problem Cable median barriers offer an option to mitigate the problem Many DOTs are installing cable barriers because of: olow costs oease of installation oadaptability for sloped conditions Research has shown that effectiveness is related to: obarrier design (number & height of cables, tensioning) oconfiguration of the median (shape, width, slopes, depth) olateral position Objective - evaluate vehicle-to-barrier interface for placement in flat-bottomed medians with varying widths and side slopes Slide 3 Federal Highway Administration Department of Transportation Vehicle Dynamics Analysis: Point 2. Point 1. Slide 4 Federal Highway Administration Department of Transportation Research Factors & Assumptions: Vehicle Models: -2000P - 820C - Mid-size Sedan Shoulder Median Median Barrier Near Side Impact Far Side Impact Initial Speeds: 50, 70, 100 km/hr Approach Angles: 5 to 25 deg 5 o 25 o Slide 5 Federal Highway Administration Department of Transportation Simulation Assumptions: Median has firm surface. Ploughing into the surface by tires is negligible Non-tracking vehicle paths were not considered Initial velocity was assigned to vehicle as it left the shoulder. Some deceleration occurred crossing the median. No driver reactions (e.g., steering, braking) Vehicle full-engagement with a minimum of one cable is needed to capture vehicle Slide 6 Federal Highway Administration Department of Transportation Validation: Comparisons of Simulation to Crash Test Results Slide 7 Federal Highway Administration Department of Transportation Effective Interface Conditions: To avoid over-ride, the top cable should contact the vehicle above Point 1 (lower critical point) To avoid under-ride, lower cable should contact the vehicle below Point 2 (upper critical point) These conditions should be met for all approach angles, speeds, and different vehicles Point 2 Point 1 Slide 8 Federal Highway Administration Department of Transportation Point 1 Trajectories All Cases & Maximums: Slide 9 Federal Highway Administration Department of Transportation Point 2 Trajectories All Cases & Minimums: Slide 10 Federal Highway Administration Department of Transportation Maximum and Minimum Heights Override Limit Underride Limit Slide 11 Federal Highway Administration Department of Transportation Effective Lateral Placement: (10:1 slopes 36 width not including shoulders generic 3 cable) Slide 12 Federal Highway Administration Department of Transportation Effective Lateral Placement: (10:1 slopes 36 width including shoulders generic 3 cable) Slide 13 Federal Highway Administration Department of Transportation Evaluating Flat Bottom Median Profiles: Median Widths 26-58 ft Slopes 8:1, 6:1, 4:1 Shldr 10 ft Widths 25, 40, 60, and 100 ft Slopes 4:1, and 6:1 Shldr 2ft4ft6ft Analyzed varied flat-bottomed median profiles: - Median width (25, 40, 60, & 100 ft) - Median depth (2, 4, & 6 ft) - Median slopes (4:1 and 6:1) Vehicle dynamics simulations were conducted for each combination of these factors. Slide 14 Federal Highway Administration Department of Transportation Cable Barrier Systems Considered: Brifen System Cable heights o480 mm (18.9 in) o630 mm (24.8 in) o780 mm (30.7 in) o930 mm (36.6 in) Gibraltar System Cable heights 508 mm (20 in) 635 mm (25 in) 762 mm (30 in) 990 mm (39 in) Slide 15 Federal Highway Administration Department of Transportation I-694 Medians Slide 16 Federal Highway Administration Department of Transportation I-694 Section A Median Profile Slide 17 Federal Highway Administration Department of Transportation I-694 Section A Median Profile Median Widths 26-58 ft Slopes 8:1, 6:1, 4:1 10 ft 51 ft Slope 6:1 3ft 15 ft 51 ft Slope 6:1 4ft 3 ft Two profiles were analyzed to account for depth variation Slide 18 Federal Highway Administration Department of Transportation I-694 Section A Median Profile Slide 19 Federal Highway Administration Department of Transportation I-694 Section A Median Profile Slide 20 Federal Highway Administration Department of Transportation I-694 Section B Median Profile Slide 21 Federal Highway Administration Department of Transportation I694 Section B Median Profile 51 ft Slope 10:1 2.5ft 1 ft Slide 22 Federal Highway Administration Department of Transportation I694 Section B Median Profile Slide 23 Federal Highway Administration Department of Transportation I-35W Profiles Slide 24 Federal Highway Administration Department of Transportation I-35W Section A Median Profile Slide 25 Federal Highway Administration Department of Transportation I-35W Section A Median Profile Median Widths 26-58 ft Slopes 8:1, 6:1, 4:1 10 ft 33 ft Slope 4:1 2.5 ft 13 ft 33 ft Slope 4:1 3.5 ft 5 ft Two profiles were analyzed to account for depth variation Slide 26 Federal Highway Administration Department of Transportation I-35W Section A Median Profile Slide 27 Federal Highway Administration Department of Transportation I-35W Section A Median Profile Slide 28 Federal Highway Administration Department of Transportation I-35W Section B Median Profile Slide 29 Federal Highway Administration Department of Transportation I35W Section B Median Profile Median Widths 26-58 ft Slopes 8:1, 6:1, 4:1 10 ft 49 ft Slope 4:1 2.5 ft 29 ft 49 ft Slope 4:1 3.5 ft 21 ft Slide 30 Federal Highway Administration Department of Transportation I-35W Section B Median Profile Slide 31 Federal Highway Administration Department of Transportation I-35W Section B Median Profile Slide 32 Federal Highway Administration Department of Transportation I-35W Section C Median Profile Slide 33 Federal Highway Administration Department of Transportation I-35W Section C Median Profile Median Widths 26-58 ft Slopes 8:1, 6:1, 4:1 10 ft 29 ft Slope 4:1 2.5 ft 9 ft 29 ft Slope 4:1 3.5 ft 1 ft Slide 34 Federal Highway Administration Department of Transportation I-35W Section C Median Profile Slide 35 Federal Highway Administration Department of Transportation I-35W Section C Median Profile Slide 36 Federal Highway Administration Department of Transportation TH-13 Profiles Slide 37 Federal Highway Administration Department of Transportation TH 13 Section A Median Profile Slide 38 Federal Highway Administration Department of Transportation TH 13 Section A Median Profile Three profiles were analyzed to account for width variations Slide 39 Federal Highway Administration Department of Transportation TH 13 Section A Median Profile 28 width Slide 40 Federal Highway Administration Department of Transportation TH 13 Section A Median Profile 35 width Slide 41 Federal Highway Administration Department of Transportation TH 13 Section A Median Profile 42 width Slide 42 Federal Highway Administration Department of Transportation TH 13 Section B Median Profile No analyses performed (3:1 sloped section) Slide 43 Federal Highway Administration Department of Transportation TH 13 Section C Median Profile Slide 44 Federal Highway Administration Department of Transportation TH 13 Section C Median Profile Two profiles were analyzed to account for width variations Slide 45 Federal Highway Administration Department of Transportation TH 13 Section C Median Profile 18 width Slide 46 Federal Highway Administration Department of Transportation TH 13 Section C Median Profile 25 width Slide 47 Federal Highway Administration Department of Transportation TH 13 Section D Median Profile Slide 48 Federal Highway Administration Department of Transportation TH 13 Section D Median Profile One profiles was analyzed Slide 49 Federal Highway Administration Department of Transportation TH 13 Section D Median Profile 20 width Slide 50 Federal Highway Administration Department of Transportation TH-55 Profiles Slide 51 Federal Highway Administration Department of Transportation TH 55 Section E Median Profile Slide 52 Federal Highway Administration Department of Transportation TH 55 Section E Median Profile Three profiles were analyzed to account for width variations Slide 53 Federal Highway Administration Department of Transportation TH 55 Section E Median Profile 23 Slide 54 Federal Highway Administration Department of Transportation TH 55 Section E Median Profile 28 width Slide 55 Federal Highway Administration Department of Transportation TH 55 Section E Median Profile 31 width Slide 56 Federal Highway Administration Department of Transportation TH 55 Section F Median Profile Slide 57 Federal Highway Administration Department of Transportation TH 55 Section F Median Profile Two profiles were analyzed to account for width variations Slide 58 Federal Highway Administration Department of Transportation TH 55 Section F Median Profile 23 width Slide 59 Federal Highway Administration Department of Transportation TH 55 Section F Median Profile 31 width Slide 60 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile Slide 61 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile Six profiles were analyzed to account for width variations Slide 62 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile 24 width Slide 63 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile 30 width Slide 64 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile 40 width Slide 65 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile 50 width Slide 66 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile 60 width Slide 67 Federal Highway Administration Department of Transportation TH 55 Section G Median Profile 100 width