In streets paved with granite setts, wood blocks or asphalte, the same material is used for the channelling, the setts or blocks being however bedded in line with the channel instead of transversely as in the street itself.
The channel gutter should take the slope of the roadway and the granite kerb should show from 3 to 5 inches above it. At paved crossings it is well to keep them level with the kerb so that pedestrians may step off the path on to the crossing without any drop, or if there is any water in them at such points, it is a good plan to let the edge of the crossing drop rather suddenly towards the kerb, so that the ordinary stride of the pedestrian carries him on to the level.
Gulley gratings or buddle holes should be placed along the line of channel at such intervals as may be found necessary. A great number of different forms have been from time to time introduced for this purpose, the objects to be considered being:
(1.) Sufficient area to carry off all the water.
(2.) Not easily choked on surface by leaves or other debris.
(3.) Sufficiency of pit to retain all sand or road detritus and prevent it being washed into the sewer.
(4.) The least possible obstruction to the traffic.
(5.) Constructed so that the pit may easily be cleaned out.
(6.) Trapped so as to prevent the escape of sewer gas.[111]
(7.) The drain from it should be easily freed of any obstruction.