80 G. H. KNIBBS. 



interests in such a way as to involve a minimum of alteration 

 with its attendant expense and difficulty. 



Outside such comprehensive considerations as the foregoing, 

 the element of localising types of street depends solely upon their 

 main function. For the leading lines of heavy traffic light grades 

 are required, and widths proportionate to the ultimate magnitude 

 of the traffic ; special consideration is necessary to guard against 

 inadequate provision at such points of congestion as depots and 

 freight-yards of all kinds, railway stations, and similar places. 

 It" the city is to possess a military centre, ample provision must 

 also be made to facilitate the mobilisation and despatch of troops, 

 war material, etc. The lighter traffic of merely residential streets 

 involves less attention to gradient, their character depending 

 solely upon their intended surroundings. For example, streets 

 leading to each class of buildings would be designed in agreement 

 therewith, those to be adorned on each side by palatial buildings 

 possessing a collateral magnificence, whilst streets leading to 

 localities populated by the poorer classes would be less pretentious; 

 though they, too, might well be made picturesque with foliage 

 trees. 



10. Grade and cross-section of streets. — Ordinarily a grade of 

 ^ % in the longitudinal section of a street will suffice for surface 

 drainage; for localities subject to tropical downpour this might 

 be slightly increased, and where the rate of fall is unusually light 

 slightly diminished. For vehicular traffic a grade of 10 % may 

 be treated as a maximum, and that design which avoids heavy 

 grades on the main lines of traffic is of course the best in respect 

 thereof. In commercial and industrial, and even in residential 

 parts of the city, the level of the streets may, with advantage, be 

 1 or 1 J metres, say 3 to 5 feet, above the general level ; on the 

 other hand, in suburban residential localities, the street level 

 ought to be the lower. The usual cross-section, viz., a carriage 

 or roadway with raised footpaths, would, of course, in the case of 

 the wider streets, be departed from. In the widest streets of all 

 one part of the roadway might be devoted to heavy, and another 



