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Cross-Section Elements: Introduction

Federal Highway Administration

The cross section of a road includes some or all of the following elements:

• Traveled way (the portion of the roadway provided for the movement of vehicles, exclusive of shoulders)
• Roadway (the portion of a highway, including shoulders, provided for vehicular use)
• Median area (the physical or painted separation provided on divided highways between two adjacent roadways)
• Bicycle and pedestrian facilities
• Utility and landscape areas
• Drainage channels and side slopes
• Clear zone width (i.e., the distance from the edge of the traveled way to either a fixed obstacle or non-traversable slope)

Considered as a single unit, all these cross-section elements define the highway right-of-way. The right-of-way can be described generally as the publicly owned parcel of land that encompasses all the various cross-section elements.

Some decisions about cross section are made during project development, such as the capacity and number of lanes for the facility. Other decisions, such as functional classification, are made earlier in the process. Within these parameters, the Green Book guidelines recommend a range of values for the dimensions to use for cross-sectional elements. Deciding which of the elements to include and selecting the appropriate dimensions within these ranges is the role of the designer.

In selecting the appropriate cross-section elements and dimensions, designers need to consider a number of factors, including the following:

• Volume and composition (percent trucks, buses, and recreational vehicles) of the vehicular traffic expected to use the facility
• The likelihood that bicyclists and pedestrians will use the route
• Climatic conditions (e.g., the need to provide storage space for plowed snow)
• The presence of natural or human-made obstructions adjacent to the roadway (e.g., rock cliffs, large trees, wetlands, buildings, power lines)
• Type and intensity of development along the section of the highway facility that is being designed
• Safety of the users

The most appropriate design for a highway improvement is the one that balances the mobility needs of the people using the facility (motorists, pedestrians, or bicyclists) with the physical constraints of the corridor within which the facility is located.