In constructing a road, the construction crews should follow a specific sequence. First, they clear the area through which the road must pass of trees, stumps, brush, boulders, and other debris. The width of the clearing varies greatly but is always at least 12 feet greater than the roadway width; that is, the crew should clear at least 6 feet behind the construction limit on both sides of the road.

The next step is the grading operations and the laying of cross-drain pipes, or culverts. The grading operations are carried on by the Equipment Operators until the subgrade is completed. In fill areas, the grading is brought up in layers and compacted. In cuts, the excavation is carried on until the subgrade elevation is reached, and then the earth is compacted. Throughout this step of the road construction, workers place the culverts when and where required. These culverts are placed in their appropriate positions and at the required slopes according to the roadway plans.

After the subgrade is completed, Equipment Operators place abase course on the subgrade. The base course material can be gravel, sand, crushed stone, or more expensive and permanent materials. Finally, the Equipment Operators place a surface course over the base. This material can be sand, asphalt, blacktop, concrete, or similar materials.

In some cases, traffic may be allowed to travel over the subgrade itself. In others, traffic may require only a gravel or stone surface. A high-speed road, however, requires abase and a hard, durable surface.

Sections are used for a variety of purposes during the various phases of road design and construction. One purpose is to define what the materials and design

Figure 3-6.Typical section.

configuration of the completed road should be. You will also use sections for staking out roads, for determining earthwork requirements, and for determining how closely the completed road conforms to its original design.