ROAD MODELS. 9 
gravel, macadam, or other road of crushed stone. These drains arc 
generally a little deeper than the subgrade and slope toward the side 
ditches, to which they carry the water. They are filled with crushed 
stone to a depth of 6 or 8 inches and are covered over with earth. The 
shoulder drains are required in clay soils and are placed at the low 
points in the grade as well as at frsquent intervals on flat grades. 
The telford base is extensively used in locations on swampy or 
marshy ground. 
The guard rail shown in the model is desirable along steep slopes to 
protect travelers. The fence is painted to prolong its life. The 
white color enables the public to discern it at night. The posts are 
about 6 inches in diameter and about 7 feet long, and are set in the 
ground to a depth of 3 J feet. About 18 inches from the ground a 
plank, 2 by 6 inches, is notched into the posts. The top rail is then 
placed about 18 inches above the top edge of this plank. It may be 
either 4 by 4 inch timber, notched into the top of the post, or a plank, 
2 by 6 inches, spiked to the top of the post, which has been sawed off 
to a slope of 3 inches. 
Section B shows a V drain base with a side outlet. 
The V drain base, when used in through cuts, is cheaper than the 
telford method with two side drains, especially in a section of country 
where field stone abounds. It, like the telford, is often used in wet 
and spongy ground. The water flows to and along the point of the 
V drain (i) until a suitable outlet can be secured. The center is 
usually excavated 2 feet and the sides about 16 inches below the 
finished grade. The material excavated is thrown to the sides, 
forming the shoulders. In swamp sections it is sometimes necessary 
to haul material for the shoulders. The V drain is then filled with 
stone to a depth of 18 inches at the center and 10 inches at the sides. 
These stones grade from 8 inches in thickness down to a few inches. 
The large-sized stones are placed at the bottom, while the small stones 
arc used at the top. The surface should then be rolled and the 
surfacing material spread and rolled. V drains are sometimes built 
of brickbats, slag, or even sand, or any material that will permit the 
water to seep rapidly to the point of the V. This type of construction 
permits the use of field stone of an inferior type and assists in clearing 
many farm lands of an otherwise waste product. 
Section C shows a center drain with laterals and cobble gutters. 
The center drain with laterals, sometimes called a blind or French 
drain, furnishes another mode of draining the foundation of a road. 
As with the V drain, the water is brought to the center of the road 
and conducted to some suitable outlet. The model shows these 
drains about 2 feet deep, about 12 inches wide at the bottom, and 
about 18 inches wide at the top. A drain tile is placed at the bottom 
87538°— Bull. 220—15 2 
