Page 9 - Cat Motor Grader Application Guide AEGQ0947-00

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Road Cross Section Terms

Much of today’s motor grader work involves the maintenance, snow clearing, and building county/ township type roads. This includes smoothing, shaping the travel surface, and providing drainage to prevent road deterioration in inclement weather. Keep in mind, the most important item in road maintenance is providing and maintaining a good drainage system.

The diagram below shows the cross section of a typical road and the terms used to describe each component.

1. Road Width. Normally 8 to 12 feet (2.4 to 3.7 meters) wide per vehicle lane but will vary depending on the width of the road right of way (ROW). Where the ROW is available, county road width including shoulders will be between 26 and 30 feet (7.9 and 9.1 meters) wide.

2. Road Shoulder. Normally 1 to 8 feet (0.3 to 2.4 meters) wide depending on the type of road being constructed.

3. Road Crown. 1

4 to 1

2 inch raise per foot (0.6 to 1.3 centimeter raise per meter) from the shoulder to the center of the road. This will vary with the type of wear surface used and annual rainfall expected.

4. Travel Wear Surface. Varies with geographic location and the type of road being constructed. The material can be dirt, gravel, crushed rock, asphalt or concrete.

5. Road Ditch Slope. This slope will vary depending on the type of road being constructed, the material type, ditch depth, and width of ROW. Whenever possible, keep ditch slopes flatter than 2:1. (In some geographic areas this is known as the fore slope or road shoulder slope.)

M S E R I E S M O T O R G R A D E R S A P P L I C A T I O N G U I D E

7

Figure 5. Crowned Cross Section — Straightaway

Figure 6. Super Elevation Cross Section — Curves

Page 9 - Cat Motor Grader Application Guide AEGQ0947-00

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