ROADS AND ROAD BUILDING 269 



packed ; but in cities, for street work, various materials are used in 

 building up a foundation. 



Coal cinders and screenings from coke are usually very satis- 

 factory for this purpose. Waste products from factories are 

 available in many localities and may be used to good advantage. 

 The waste material from fire-clay brick, sewer pipe, broken and 

 unused pieces of shells from button factories are frequently 

 used and are found very satisfactory for foundation work. In 

 regions where there are large smelters slag is used for the same 

 purpose. 



In cities, after the ground has been leveled and rolled, a 

 foundation of gravel and concrete is often provided before 

 the paving is put down, but on country roads this is too 

 expensive. 



The surface should have sufficient slope to cause all rain water 

 to drain off easily and quickly. The lateral slope from the center 

 to either side should be about one in twelve. Some road builders 

 have a continuous curve for the surface; others have a curve at 

 the center, while the sides have an even slope. When we speak of 

 the lateral slope as being one in twelve, we mean that there is a 

 slope downward of one inch to the foot. On this scale a street 

 twenty-four feet wide would be one foot higher at the center of 

 the crown of the road than at either side. In many instances 

 the center of the crown is only from five to eight inches higher than 

 each side of the street. 



The width of the surface should be great enough to accom- 

 modate all traffic, so that vehicles of all kinds may have suffi- 

 cient room to pass each other without difficulty. Wherever pos- 

 sible, bridges should be practically of the same width as tho 

 road. 



In this country the universal custom is for each driver to turn 

 to his right in passing any vehicle which he may meet in his road, 

 but this custom varies in different countries. In many parts of 

 Canada drivers of vehicles turn to the left instead of the right. 

 Custom demands that heavily loaded wagons be given the right 

 of way, and that empty wagons or light-going vehicles turn either 

 to the right or left, as the situation may demand. 



Wherever deep fills are made in the roadbed, the surface should 



