ROAD DRAINAGE. I9I 



known plan for road drainage. This method of drain- 

 age is shown in Fig, 37, which represents a road surface 



Fig. 37. — ^Proper Location for Surface Ditches and Tile Drains in Road 



Construction. 



18 feet wide, one half of which is gravel surface and the 

 other half earth surface. This is regarded as the most 

 economical method of road improvement at low cost 

 now in use where a hard road is desired. The earth 

 track is the favorite one for use in dry weather and 

 for light loads, while the gravel track is used for heavy 

 loads and at times when the dirt track is wet. In this 

 way the wear is shared by the two and both tracks 

 easily kept in order. 



Sub-drainage has lessened the cost of all hard roads 

 by demonstrating that a less thickness of road covering 

 or road metal is required than was formerly thought 

 necessary. All experienced road-builders now em- 

 phasize the importance of complete underdrainage in 

 constructing hard roads. With a firm foundation 

 which underdrainage secures, it is only necessary to 

 construct and maintain a good wearing surface. With 

 good soil drainage, much of the height of large em- 

 bankments may be reduced by lowering the line of sat- 

 uration instead of raising the road surface by costly 

 earth work where this is not required for the purpose 

 of obtaining an economical grade. 



