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R6891 CaSE OBJECTIVES

This report addresses misconceptions regarding the cost of incorporating safety features in rural road design, emphasizing that these enhancements are both necessary and cost-effective. By analyzing data from six countries, the study presents evidence on the relative safety of various design elements, optimizing costs, and safety. It outlines essential design recommendations for features like shoulders, footpaths, and drainage channels to improve road user safety. The findings aim to inform investment models and contribute to safer rural transportation.

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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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