EOAD MODELS. 7 



LOCATION AND ALIGNMENT. 



When a new road is to be built, or an old road rebuilt, the profile 

 should be established and the curves plotted by a competent engineer. 

 The sharp curves and steep grades should be eliminated by a proper 

 alignment or by cuts and fills. When a grade exceeds 6 feet in 100 

 feet, it is considered excessive for heavy traffic. A curve with less 

 than a 200-foot radius is considered dangerous for fast traffic. Em- 

 bankments, trees, and shrubs which obscure the line of sight on 

 sharp curves should be cut back in order that rapidly moving vehi- 

 cles approaching each other may be able to pass without accident. 



In selecting the location for a new road, low, swampy ground or 

 ground subject to overflow should be avoided. The road should be 

 located on solid ground. In mountainous or hilly sections it should 

 be located on the sidehill slopes, with southern or western exposure, 

 where the natural drainage is good, and not in creek or river bottoms. 



The road should be as straight as possible, but a good grade is pre- 

 ferred to straightness. Generally a road should be located around 

 long steep inclines instead of over them. If this is impracticable 

 then the length of the road up the incline should be increased suffi- 

 ciently to obtain a good grade. Dangerous railroad grade crossings 

 should be avoided by relocation of the road or by overhead bridges 

 or underpasses. 



Plate IV, figure 2, illustrates the relocation of an old road. To the 

 right is shown the old earth road, with such characteristic features 

 as steep grades, poor alignment, dangerous grade crossings, unsafe 

 wooden bridge, and inadequate drainage. The dilapidated farm 

 buildings and the old district schoolhouse featured on the model, 

 with their unsightly and insanitary surroundings, are the usual 

 accompaniment of such a road. To the left is shown the new road, 

 located on higher ground, along sidehill slopes, with easy grades and 

 pleasing, practical alignment. The grade crossing has been elimi- 

 nated. A bridge and permanent culverts have been built and good 

 drainage provided as well as a well constructed and maintained 

 macadam surface. The sightly farm buildings and attractive con- 

 solidated district schoolhouse are supplied with pure water by means 

 of windmill and reservoir. 



FOUNDATION, OR SUBGRADE, AND SHOULDERS. 



In the construction of all types of gravel or macadam roads it is 

 necessary, in order to obtain the most economical results, to prepare 

 the foundation, or subgrade, and shoulders of the road carefully. 

 After the subgrade has been properly shaped and before any broken 

 stone or other material is put on, it should be thoroughly rolled and 

 compacted. Water-puddling may be resorted to in case the soil 



