In the Punjab the widths of roadways between the kerbs and parapets of bridges respectively have been fixed as follows:—
| Kind of Road. | Near Towns.[20] | In the Country.[21] | ||||||
|---|---|---|---|---|---|---|---|---|
| Kerbs. | Parapets. | Kerbs. | Parapets. | |||||
| Provincial | 22 | 23 | ·5 | 16 | 17 | ·5 | ||
| District | 18 | 19 | ·5 | 14 | 15 | ·5 | ||
| Village | 14 | 15 | ·5 | 8 | ·5 | 10 | ||
[20] The figures show the maximum. The general width should be the same as for neighbouring bridges on the same road.
[21] The parapets should be whitewashed so as to be visible at night.
Fig. 15.
[Fig. 15] shows a head regulator for a distributary. The scale is 10 feet to an inch. It has a double set of grooves for the insertion of the planks with which the regulation is effected. Only one set of grooves is ordinarily used, but when the distributary has to be closed for silt clearance and all leakage stopped, both sets of grooves can be used and earth rammed in between the two sets of planks. The floor is shown a foot lower than the bed of the distributary. This reduces the action of the water on the floor, and enables the bed of the distributary to be lowered if ever the occasion for this should arise. This is a good rule—in spite of the fact that in re-modellings the tendency is for the beds to be raised—for all regulators or bridges, a raised sill being added (in regulators) to reduce the length of the needles or the number of the planks. Such sill should, where needles are to be used, be fairly wide, especially if regulation is to be done while the masonry is somewhat new. The distributary shown has a bed width of 10 ft. The span of the two openings in the head might have been four feet each, but are actually five feet, and this enables the distributary to be increased in size at any time. The pitched portion of the channel tapers. Unless needles are used, instead of horizontal planks, spans are not usually greater than 5 or 6 feet. Longer spans would give rise to difficulties in manipulating the planks. Sometimes distributary heads are built skew, but there is seldom or never any good reason for this. A curve can always be introduced below the head to give the alignment the desired direction.[22] The small circles shown on the plan are “bumping posts.” On the left is shown a portion of the small raised bank at the edge of the road.
[22] The curve can be quite sharp (see [Chap. I., Art. 2]), and can be made, if necessary, within the length of the pitching.
Fig. 16.