Roadway Surveys – Design and Layout

In this course, the surveyor will learn the surveying procedures used to perform a roadway route and design layout survey. Although global positioning systems (GPS) have revolutionized the surveying industry, there are times and locations where that equipment is unavailable due to breakage, dead batteries, or it cannot be employed, such as in dense forests or tunnels. Therefore, it is important to know and understand the fundamentals of laying out a route using the basic total station and level. As such, we shall first explore the conventional methods of survey layout and then expand on the same tasks as performed with GPS.

We will first discuss the preliminary stages of performing a road route survey, which involves outlining a reconnaissance survey, conducting a preliminary survey, and then performing the final location survey. Topics commonly found in a construction route survey will be discussed, such as the procedures for various types of staking, the use of stationing, and the laying out of drainage topography, as well as stormwater structures.

Next, the geometric design of roads is addressed and covers topics such as locating points along horizontal and vertically aligned curves using angles and distances (curve geometry), curve formulae, arc and chord definitions, and the use of tabular or empirical data to expedite design. The issue of circumventing obstacles along the route alignment, as well as setting the alignment using a fixed point, is discussed. Types of curves outlined include simple horizontal, compound, reverse, transition spirals, and vertical.

Additionally, the surveyor will learn some of the pertinent design principles of geometric roadway design used by transportation designers. These include the use of superelevation (or banking of curves), tangent-to-curve transition, sight distances, and design speed.