Highway Construction Surveying

Highway surveying is a specialized type of land surveying generally conducted for government agencies. A highway survey is often conducted during the highway planning stages. During the construction project, a highway construction survey can ensure that the process is going as it should and that the highway is located precisely where it should be. After the highway is built, a highway survey can be used to provide an accurate layout of roadways, utilities, storm drainage systems, overhead wires, nearby buildings, and other features of the landscape.

A construction surveyor is often involved in the placement process. This requires a survey of the existing terrain to find the easiest route. Highway construction surveys are particularly concerned with areas where dirt must be moved, noting to what level and grade. Often the goal of this survey is to determine the appropriate route where the least amount of land will need to be moved. An engineer can use the survey data to determine where the dirt should be moved to reduce the total amount of dirt relocation.

Not only do surveyors determine how the land must be prepared before the highway can be constructed, but they also assist engineers in the mapping of optimal routes. This includes not only grading (slopes) but also curves and the creation of tunnels or other features along the highway route. It is necessary to understand the geographic restrictions and the layout of the area before attempting to determine the best route.  Because of the natural landscape, as well as existing buildings and other features, few highways are able to run perfectly straight along their entire length. One of a surveyor's many jobs during highway construction is to aid in the mapping of this route. The most challenging part of highway planning is often the necessity of bridges or tunnels. Surveyors provide input on their location, and also monitor the highway construction process to ensure that they are located correctly.

Once the dirt has been graded and leveled, a surveyor will again survey the area to ensure that the land has been correctly prepared according to the plans. Then, construction begins. Before the advent of GPS technology, this involved the use of surveying stakes to mark the road edges. Today, GPS has eliminated this process, making it much easier to ensure that the road is aligned with the plans.

Once the road is built, surveys may be required for a wide variety of reasons, including road repair or maintenance. Highway surveys are also used during the process of accident reconstruction and investigations. The process of taking road measurements to construct a survey once required closing of the entire road so that the surveying team could set up equipment on the road's surface. Today, specialized laser equipment allows this to be done from the roadside, virtually eliminating the need for lane closures due to surveying. The highly accurate data delivered by these systems allows for the creation of detailed 3D maps showing not only the roadway but also barriers, overhead wires, and other features.

Charles Iner, RLS
November 2009