Median Cross-Section Design for Rural Divided Highways (2014) / Chapter Skim
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Pages 83-102
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From page 83... ...
83 C H A P T E R 5 Crash modeling is a relatively crude tool for determining the effects of individual roadway or roadside design factors. Vehicle dynamics simulation provides a much more direct and experimentally controlled method to examine these effects.
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84 processes during driving. Although VDANL was originally designed for passenger cars, light trucks, and multi-purpose vehicles, DVM has only been created for passenger cars and Class 8 tractor trailers.
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85 ment these situations, the CarSim driver model was used with representative target point trajectories. A third steering scenario, the "no steer" condition in which the driver takes his/her hands completely off of the steering wheel, was also modeled.
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86 both with an anti-lock braking system (ABS) onboard.
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87 combinations accounted for the remaining vehicles on the road (60)
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88 0 5 10 15 20 25 Pe rc en t o f A ll Ro llo ve r S ce na rio s (% ) 1V:6H 60 ft V 1V:6H 40 ft V 1V:6H 60 ft V Median Profile 1V:5H 60 ft Trap.
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89 0 3 6 9 12 15 Pe rc en t o f A ll R ol lo v er S ce na rio s (% ) 1V:4H 1V:5H 1V:6H 1V:8H1V:7H 1V:9H 1V:10H Median Slope Figure 5-5.
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90 0 1 2 3 4 5 6 7 4:1 5:1 6:1 7:1 8:1 9:1 10:1 Opposing Travel Lane Back Slope Post-Swale Pre-Swale Downslope Original Travel Lane Original Shoulder Pe rc en t o f V eh ic le s to R ol lo ve r i n Ea ch A re a (% ) Figure 5-7.
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91 0 5 10 15 20 25 30 35 40 4:1 5:1 6:1 7:1 8:1 9:1 10:1 Pe rc en t o f V eh ic le s to C om e to a R es t i n Ea ch A re a Opposing Travel Lane Back Slope Post-Swale Pre-Swale Downslope Original Travel Lane Original Shoulder Figure 5-8. End locations for non-rollover simulation runs for medians of varied slope.
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92 12.19 14.02 15.85 17.68 19.51 21.24 23.16 0 3 6 9 12 15 Pe rc en t o f A ll Ro llo ve r S ce na rio s (% ) Median Width (m)
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93 opposing lane, thus resulting in an increased probability of a head-on collision. Using the same ratio of incursion into the opposing lane to rollover at any time during the simulation as used in the median slope investigation, Figure 5-12 shows that a vehicle entering a 12-m (40-ft)
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From page 94... ...
94 0.1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Ground Clearance (m)
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95 is representative of the SUV and truck population. There is clearly a disparity of about 20.5 cm (8 in.)
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96 As the vehicles continued down the slope, the two modes appeared to separate again. At the swale point, most vehicles impacted the back slope at roughly the same height but major differences between vehicles emerged thereafter.
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97 0 20 40 60 80 100 120 -5 0 5 10 15 20 25 30 Longitudinal Position (m)
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98 0 1 2 3 4 5 6 7 8 -10 0 10 20 30 40 50 60 70 Simulation Time (sec)
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99 0 20 40 60 80 100 120 140 160 180 200 -5 0 5 10 15 20 Longitudinal Distance (m)
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100 guidance for the design of median cross sections on divided highways. From the simulation data, general trends depicted the relationship between a design parameter (median shape, width, etc.)
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101 4H:1V 5H:1V 6H:1V 7H:1V 8H:1V 9H:1V 10H:1V 12.19 14.02 15.85 17.68 19.51 21.24 23.16 Median Slope M ed ia n W id th (m ) Rollover Cross-Over Cross-Over Prone Median Profiles Rollover Prone Median Profiles Figure 5-24.
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From page 102... ...
102 a median encroachment. The median cross-section simulated was 18 m (60 ft)
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