The interception capabilities of slotted drains as pavement surface drainage systems

The following two slotted drain installation scenarios were reviewed in this paper: a slotted drain operating individually without a median barrier and a slotted drain operating with an adjacent barrier installed along the longitudinal length of the drain. The interception capability of the two installation scenarios was experimentally reviewed and compared while imitating various conditions typically expected on South African pavements. The applied sheet flow, slotted inlet sizes and pavement slopes (longitudinal and cross slopes) were varied throughout the experiment. Interception efficiencies of the slotted inlets were experimentally calculated as a ratio of total intercepted sheet flow to the total sheet flow applied to the pavement layouts. The sheet flow applied during the experiment was analysed to estimate the rainfall intensities and flow depths that can typically occur on the different pavements for which the interception capability of the slotted inlets was reviewed. It was estimated that rainfall intensities of more than 1 000 mm/hr and flow depths higherthan 10 mm were imitated during the experiment. More than 98% of the maximum applied sheet flow of approximately 3.0 £/s/m was intercepted by the 30 mm slotted inlets regardless of the pavement slope values and type of slotted drain layout. The conclusion reached was that both these slotted drain installation scenarios operating in practice for the conditions tested would have the capability to sufficiently remove the surface water to promote road safety during wet pavement conditions.