A treatise on highway construction . flevels into an ascending road is where such levels will advance theroad towards it? objective point; where this is the case there willbe no loss of either length or height, and it will simplyJae exchang-ing a level road below for a level road above. 609. Establishing the Grade.—When the profile of a proposedroute has been made, a grade line is drawn upon it (usually in red)in such a manner as to follow its general slope, but to average itsirregular elevation and depressions. If the ratio between the whole distance and the height of theline is less than the

- Image ID: 2AWP0P6
A treatise on highway construction . flevels into an ascending road is where such levels will advance theroad towards it? objective point; where this is the case there willbe no loss of either length or height, and it will simplyJae exchang-ing a level road below for a level road above. 609. Establishing the Grade.—When the profile of a proposedroute has been made, a grade line is drawn upon it (usually in red)in such a manner as to follow its general slope, but to average itsirregular elevation and depressions. If the ratio between the whole distance and the height of theline is less than the
The Reading Room / Alamy Stock Photo
Image ID: 2AWP0P6
A treatise on highway construction . flevels into an ascending road is where such levels will advance theroad towards it? objective point; where this is the case there willbe no loss of either length or height, and it will simplyJae exchang-ing a level road below for a level road above. 609. Establishing the Grade.—When the profile of a proposedroute has been made, a grade line is drawn upon it (usually in red)in such a manner as to follow its general slope, but to average itsirregular elevation and depressions. If the ratio between the whole distance and the height of theline is less than the maximum grade intended to be used, this linewill be satisfactory; but if it be found steeper, the cuttings or thelength of the line will have to be increased: the later is generallypreferable. 610. The apex or meeting point of all grades should be roundedoff by a vertical curve shown in Figs. 51 to 53. The formula for these curves is given in Art. 935. LOCATION OF COUNTRY ROADS. 481 EXAMPLES OF THE APPLICATION OF VERTICAL CURVES.. Figs. 51 to 53. 482 HIGHWAY CONSTKUCTION. 610a. Geological Considerations. — The extent to whichgradients can be diminished by curves or cuttings is often deter-mined by the geological structure of the country. The cost bothof construction and ihaintenance of roads may be considerablyincreased by neglecting to investigate the geology of the areatraversed. For this purpose both the nature of the rocks as wellas the direction of their stratification must be taken into account.Where the road follows the natural surface of the ground, the stabil-ity of its foundation is largely influenced by the nature of theunderlying rock. Bogs and marshy swamps present difficultieswhich ought particularly to be avoided, and all ground liable tofloods should be carefully noted. Even in strata which are appar-ently solid and .homogeneous the presence of springs may causecsrtain portions of a road to be continually wet. This difficulty ismore especially common at the