DRIVES, AVENUES, AND SERVICE ROADS. 



No paper scheme for a drive of this kind can possibly be successful. Only by first 

 planning on paper, then pegging on to the ground, adjusting by the eye and re-surveying 

 on to paper, readjusting and repeating this process several times, can the best route be 

 decided on. For the purpose of marking out the curves on the ground, small pegs are 

 no use. Surveyors' poles are best, but where these are not immediately available, 

 slaters' laths as long as possible will do almost equally well if they are white and clean 

 so as to show up well against fallow ground, turf or brake, as the case may be. Where 

 these are used and there are sudden dips in the ground a few longer stakes will also 

 be required such as may be made from plasterers' anglebead. Dahlia stakes may be also 

 used if unpainted, but those which have the usual dark green colour are unsuitable. 



The reason for using long stakes to mark out the course of the drive will be seen 

 immediately if we peg it with short ones and then substitute long ones, putting them 

 into the holes made by the short ones. It will be at once apparent how much the 

 unevenness of the ground warps the perspective, so that curves which look nice as at first 

 pegged out would be found to be far too flat in the hollows and too sharp on the 

 breast of a hill when the inevitable grading is completed. 



In order to judge more correctly of the effect of raising the surface of the finished 

 drive above the natural level in the hollows, and lowering it at the highest points, and 

 also to test the result of substituting even gradients for the original rough hummocks 

 covering rising ground, a further expedient may be resorted to. Having fixed the long 

 pegs in position, a number of pieces of scarlet chair webbing are procured, one for each 

 peg and about eighteen inches or more long. These are loosely knotted round each 

 peg so that they can be slid up and down, but so that they will remain where placed. 

 Now cut a piece off a spare lath rather longer than the deepest cutting is expected 

 to be, and using it as a rule, slide all the pieces of webbing up or down the stake until 

 they are the height of your measure above the proposed finished level of the drive at 

 each point. By running the eye along the line of red on the stakes, a very approximate 

 idea of the ultimate result can be obtained, though due allowance must be made for 

 the fact that ciirves will look flatter on this single line of pegs than they will on a 

 drive of twelve feet or more broad. The whole can then be surveyed and marked on 

 the plan, the amount of cutting or filling at each peg being noted. 



Of course the above method of working must be subsidiary to a proper series of 

 sections prepared from measurements taken over the course of the drive with a surveyor's 

 level and plotted on to paper ; but unfortunately, in ordinary road engineering, practical 

 considerations usually determine the route and levels, while in the case of drives, aesthetic 

 factors must also be considered so that visual helps such as those described must be 

 used to assist the surveyor's measurements. 



There are two other ways in which the ordinary methods of the road or railway 

 engineer fail aesthetically when applied to drives and service roads. One relates to 

 the arrangement of his curves and the other to his gradients. The former are laid 

 down to fixed radii of circles tangent to one another or to intermediate straight lines. 

 Where aesthetic conditions are sought, these set radii must give place to catenary curves, 

 the graduated curves assumed by a chain or rope when loosely suspended between two 

 points. The reason for this is not far to seek, for a moment's reflection will show that 

 this is the curve any wheeled vehicle naturally takes (unless running on rails), and 

 consequently is the best to adopt practically as well as aesthetically. 



With regard to levels, the railway engineer's lines consist of one straight gradient, 

 or " bone " as the workman will call it, running into another or into a level stretch, 

 and it will invariably be found that, on facing a rise where there is a flatter gradient 

 below meeting a steeper one above, there will appear to be a sunk place in the surface 

 where the two meet, while when the conditions are reversed and the lower gradient is 



Practical 

 planning 

 of curved 

 drives. 



Engineers' 

 and Land- 

 scape Arch- 

 itects' 

 methods 

 contrasted. 



