Discussion. The Trend of Road Construction. Road Engineering Division.

Abstract

SO far as the relation of the margin to the carriageway affects the degree of elaboration of surface-water drainage.On the country roads, the raised margin, with or without kerb, is generally accepted as current good practice, even where no footpath or other track has to be accommodated. The merits of this lay-out, as they are preached, are that traffic does not damage the margin and that surfacewater is contained in the channel and can be collected without softening the margin by percolation.The validity of the first reason is open to serious question. Some road engineers believe that a flush margin, suitably stiffened for a few feet on either side of the carriageway, should be provided as a safety zone for traffic in difficulty due to risk of collision, etc. ; t h s principle seems to be followed as general practice in America, and in fact, where it is not provided a warning sign with the appealing wording " soft shoulders " is sometimes displayed.With regard to the drainage factor, if such flush margin falls away from the road the carriageway water can be dissipated continuously throughout its length to be soaked up by the margin or, if a surplus does accumulate a t the back of it, to be disposed of by a shallow spoon drain tapped a t appropriate places for outfall. The fear of the softening of the margin is probably a bogey anyway and has proved to be so in the Author's own area.The principle can be applied to well made embankments and, in the Author's experience, the water from the carriage does not mount up or accumulate a t particular places to such an extent as to provide the slightest risk of damage.The effect of such a policy is to provide considerable economy in the cost of surface-water drainage works and to give considerable relief with regard tg the provision, off the highway, of elaborate outfalls, as well as a general relief to the adjacent surface-water drainage system in the shape of ditches, streams, etc DiscussionMr. Floyd, in opening the Discussion, said that it was the business of a body such as the Institution to explore periodically the work that its members did. Sometimes a Paper would break new ground, whilst a t other times reliance had to be placed on a certain spontaneity, and he hoped that on the present occasion spontaneous points of view would be put forward which would be useful to many members (and to himself in particular) in sorting out their ideas on a matter which many of them were finding extremely difficult. It might be said that a certain doubt about what one happened to be doing a t the moment was one of the mainsprings