FACTORS INFLUENCING THE EFFICIENCY OF ROAD DRAINAGE GRATINGS

This paper presents the results of an industry-supported study conduct ed at Oxford Brookes University to explore the factors influencing the hydraulic efficiency of road drainage gratings. A number of full-size model grating with varying geometric characteristics have been tested on a model road surface, and an assessment made of the influence of g rating length and width, horizontal and vertical bar alignment, depth of depression, road slope, crossfall, and approaching flow width, The effect of these variables is illustrated graphically. In addition, the effect of road roughness is illustrated using previously published da ta. Grating width is found to be of greater importance than length, an d gratings with bars orientated parallel to the herb are shown to be m ore efficient than those with bars set at right angles to the kerb, Al tering the alignment of the bars in the vertical plane reduces splashi ng and increases efficiency. Depressing a grating is found to increase efficiency, and increasing road slope, crossfall and flow width appro aching a grating, reduces efficiency. The discussion is supplemented u sing others researchers' findings.