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R6891 CaSE OBJECTIVES

R6891 CaSE OBJECTIVES. Main: To combat arguments that: a) inclusion of safety features in rural road design is too expensive b) detailed design information for safer features unavailable. Provide evidence for relative safety of important design features

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R6891 CaSE OBJECTIVES

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  1. R6891 CaSE OBJECTIVES Main:To combat arguments that: a) inclusion of safety features in rural road design is too expensive b) detailed design information for safer features unavailable • Provide evidence for relative safety of important design features • Identify aspects of design where costs and safety can be optimised • Produce CaSE Design Notes • Possible inclusion in HDM/RTIM investment models

  2. R6891 CaSE : Methodology • Existing data: a highway design study in Papua New Guinea • New data: collection of accident, cost and digital video from 6 countries {Nepal, India, Botswana, Malawi, Tanzania, Zimbabwe} • Special studies in individual countries: • shoulders • side slopes • footpaths • chevron boards • yellow bars

  3. All Accidents Rate v Shoulder width Polynomial Fit 12 10 8 6 4 2 0 0.00 0.50 1.00 1.50 2.00 2.50 3.00 Shoulder width (m) Side Swipe Accident Rate v Shoulder width Polynomial Fit 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0.00 1.00 2.00 3.00 Shoulder width (m) PNG: Accident types by Shoulder width

  4. Example model comparison: Pedestrian acc.s Papua New Guinea model: Pedestrian accs/year = 4.15E-05.(AADT)1.1400.(Section Length)0.7245 .e(0.000971*Pedestrian Count).e(1.7440*AvDDD) .e(-0.912*AvDDD*Gradient) ).e(0.3728*AvSHW*Gradient) Zimbabwe model: Pedestrian accs/km/year = 0.2808(AADT)1.177.e(0.021*Pedestrian count). .e(-1.733*Carriageway width).e(0.569*Shoulder width) .e(-.0.7702 if Land use:Houses) .e(-.0.713 if Land use:shops/Industry) .e(.0.707 if Bus bay 1 side).e(0.560 if Bus bay 2 sides) .e(1.404 if Drain lining: Sealed)

  5. PNG and Zimbabwe models comparisons

  6. CaSE : Some conclusions • Different models required for different continents and possibly needed even between countries • Different models are required for different collision types • 1.5m footpaths shown to be highly cost effective • 1.5m appears to be optimum shoulder width for safety (progressively lower accident rate up to this value but higher rate above) • If sharp bend after long straight sections unavoidable, warning signs needs to be radically ‘over-designed’ - to alert effectively • Where major routes pass through villages, change in nature of road needs to be conveyed to drivers - eg. gateways, calming • Designers need to make every effort to move routes to easy terrain - where batter slopes flattened, drainage ditches shallow etc.

  7. R6891 CaSE : Outputs to complete • Final report • Prepare 4 CaSE Notes: • Surface Water Drainage Channel design • Horizontal Curves • Facilities for vulnerable road users • Roadside, village and ribbon development

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