220 



slope. A gutter of cobble-stones or kidney-stones may be constructed 

 which will make a sufficiently irregular line along the edge of the road. 

 In many cases, however, the better arrangement is to throw the water 

 off the surface of the road on to the adjoining grass surface, carrying 

 the water away from the road, where this is possible, and elsewhere 

 constructing a broad, shallow turf gutter, its outer side joining the 

 natural ground surface by insensible and varied modulations, its inner 

 side joining smoothly to the curve of the crown of the road. 



Form of The maximum gradient of the road will be determined by the char- 



Roads acter of the traffic and the character of the road surface.* Its location 



upon the topography will be determined as a matter of economics by 

 the directness and cheapness with which the road can be run to the 

 point it seeks without exceeding the maximum gradient and without 

 turns too sharp to be readily followed by the traffic. As a matter of 

 esthetics, however, the road should, as we have said, seem to fit the 

 topography with the least possible disturbance and should seem to go 

 as directly as may be from one point of interest to another. If it vary 

 from directness, it should be only for a sufficient obstacle, hill or valley, 

 or outcropping ledge or foliage mass. (See Plate 15.) If the road 

 be unimportant in character like a country lane, continuity or clean- 

 ness of curvature in its line is not essential, and indeed, often not de- 

 sirable. If the road is important enough to be, whether the designer 

 desires it or not, a considerable feature in the landscape, at least when 

 seen by the traveler upon it, then the unity of its curvature must be 

 considered. (See Plate 31.) Too great an insistence on this unity, 

 particularly through considerable portions of the length of the road, 

 may very unhappily increase the relative importance of a road which 

 should be subordinate in a design ; but sequence of curve, smoothness 

 of flow of one curve into another, is certainly desirable, if for no other 

 reason than its obvious adaptation to the passage of traffic. When a 



* There is not space here for a discussion, at a scale to be useful, of the inter- 

 acting economic considerations of road-gradient, cross-section, and surface in relation 

 to the various traffic requirements, flow of surface water, sub-surface utilities, and 

 cost of construction and maintenance. For discussion of these topics, particularly 

 in relation to larger public roads, see such books as Harger and Bonney's Highway 

 Engineer's Handbook or Agg's Construction of Roads and Pavements. 



