HIGHWAY CONSTRUCTION 21 





considerable expense, and it would he requisite to construct a much 

 greater length of road than according to the second plan, which would 

 be to form, as before, a straight road from A to B, and from ( 1 to con- 

 struct a road which should join the former at a point I ), so as to be per- 

 pendicular to it. The traffic between A or B and C would proceed to 

 the point D and then turn off to C. With this arrangement, while 

 the length of the roads would be very materially decreased, only a 

 slight increase would be occasioned in the distance between C and 

 the other two towns. The third method would be to form only the 

 two roads A C and C B, in which case the distance between A and B 

 would be somewhat increased, while that between A C or B and C 

 would be diminished, and the total length of road to be constructed 

 would also be lessened. 



As a general rule it may be taken that the last of these methods 

 is the best and most convenient for the public; that is to say, that 

 if the physical character of the country does not determine the course 

 of the road, it will generally be found best not to adopt a perfectly 

 straight line, but to vary the line so as to pass through all the prin- 

 cipal towns near its general course. 



flountain Roads. The location of roads in mountainous 

 countries presents greater difficulties than in an ordinary undulating 

 country; the same latitude in adopting undulating grades and choice 

 of position is not permissible, for the maximum must be kept before 

 the eye perpetually. A mountain road has to be constructed on the 

 maximum grade or at grades closely approximating it, and but one 

 fixed point can be obtained before commencing the survey, and that 

 is the lowest pass in the mountain range-; from this point the survey 

 must be commenced. The reason for this is that the lower slopes 

 of the mountain are flatter than those at their summit; they cover a 

 larger area, and merge into the valley in diverse undulations. So 

 that a road at a foot of a mountain may be carried at will in the 

 desired direction by more than one route, while at the top of a moun- 

 tain range any deviation from the lowest pass involves increased 

 length of line. The engineer having less command of the ground, 

 owing to the reduced area he has to deal with and the greater abrupt- 

 ness of the slopes, is liable to be frustrated in his attempt to get his 

 line carried in the desired direction. 



