13.1 Overview
For the purposes of this chapter, an intersection is defined as the area where two or more on-system roadways join or cross, including the roadway and roadside facilities for traffic movements within the area. An intersection leg is the segment of roadway connecting to the intersection that forms it. The most common intersection configuration is a four-leg intersection at which two-roadways cross one another. Three-leg intersections are also common.
It is recommended that an intersection have no more than four legs.
For intersecting legs that join private (residential or commercial) and or public (county road and city street) roads see
.
The three general types of roadway intersection crossings are:
- At grade intersections;
- Grade separations without ramps; and
- Interchanges (i.e., grade separations with ramps).
This chapter deals primarily with design of intersections at-grade. For the other two intersection types, see
.
Intersections are often the focus of business and community activity and the place where system users will share the same travel space. Intersections usually have less capacity than other parts of a roadway facility and are where most traffic conflicts occur. Design criteria for an intersection should be selected that:
- Results in a balanced and cost-effective design;
- Offers anticipated efficient operations;
- Results in low crash frequencies;
- Results in low crash severity; and
- Considers the needs of all intersection user groups.
The specific dimensional design criteria presented in this chapter are intended to be used as a guide for the new construction of intersections.
Projects that involve improving existing intersections differ from new construction in that the performance of the existing intersection is known and can guide the design process.
Additional information on the operational and safety analysis of intersections are in the
.