| 摘要 |
<p>A drainage unit (10) for use on a bridge or other elevated structure has upper apertures (16) for receiving surface water and lower apertures (15) for receiving subsurface water that has accumulated within the layers (6, 7A, 7B) making up the road. Surface water collected in the unit is prevented from entering the road through the lower apertures (15). Preferably two channels (14, 17) are defined within the drainage unit, one channel (17) being in fluid communication with the upper apertures (16) and the other channel (14) being in fluid communication with the lower apertures (15).</p> |
