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Changing Existing Locations

line, road, location, feet and gradient

CHANGING EXISTING LOCATIONS.

The problem that arises oftener than any other in country-road location is that of improving short stretches of road, where, owing to defective location, the grades are unnecessarily heavy, the length unneces sarily great, or the ground over which the road may pass such as to make its maintenance in good con dition difficult and expensive. The first of these is the most common defect of ordinary country roads, as shortness of distance has very commonly been obtained by the disregard of the desirability of light gradients, which in very many cases are easily obtainable.

The principles to be observed and methods of pro cedure in making the new location are exactly the same as in an original location, save that in this case a road already exists, and the question of economy is one of determining whether the advantages to be gained in lessened costs of transportation and maintenance is sufficient to warrant the expense of obtaining new right of way and constructing new road.

In Fig. 12 is given an example that is frequently met in the existing road abed runs over the point of a hill, with heavy gradient, while a line of very much lighter gradient might be located around the base of the hill through the pass, at e, giving a greater length of road, but much less rise and fall. The line bed in the figure has a length about 80o feet greater, a rise and fall 70 feet less, and a maximum gradient one half as steep as the line bcd. These relations are shown in the profile in Fig. 12.

If the road in question be a common earth road, I foot of rise and fall may be taken as equivalent, in the work required to haul a load over it, to 20 feet of dis tance, and the 70 feet saved by the new location would be equivalent to 1400 feet of distance. Hence, the line bed may be considered as having an equivalent length for purposes of traffic 1400 — 800 = 600 feet shorter than the line bcd. In addition to this, loads may be taken over the new line in direction b to d more than double, and in direction from d to b triple, in weight those that can be taken by the same power over the old line.

A further improvement of the line may also be possible, if the new line can join the old one at a point lower down than b, by running a lighter gradient than 5 in zoo from the point e. Thus the line e f a would give an uniform gradient of 4 per cent, but would require the construction of more new line.

In considering changes of location, it is also neces sary to take into account the interests of adjoining owners. Houses and buildings are largely located with reference to the existing position of the roads, and changes in the position of a road may involve injury to such property. The question then becomes largely one of sacrificing the interests of the users of the road, or those of the adjoining owners — a question that should be, but commonly is not, decided by consider ing what will be of most advantage to the general com munity.