 
GDOT Design Policy Manual
Chapter 7 - At Grade Intersections
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The American Association of State Highway and Transportation Officials (AASHTO) A Policy on the Geometric Design of Highways and Streets (Green Book) defines an intersection as “the general area where two or more highways join or cross, including the roadway and roadside facilities for traffic movements within the area” (2004). In addition to this definition, GDOT considers driveways essentially to be low-volume intersections. GDOT Policies relating to driveways are discussed in greater detail in Section 7.4. of this Manual.
The main objective of intersection design should be to facilitate the safety, convenience, ease, and comfort of people traversing the intersection while enhancing the safe and efficient movement of motor vehicles, buses, trucks, bicycles, and pedestrians.
7.1. Intersection Design Elements
The efficiency, safety, operational costs, and capacity of the facility depend on proper intersection design. Intersection design should be fitted closely to the natural transition paths and operating characteristics of its users. The five basic elements that should be considered in intersection design are:
- Human Factors - driving habits, the ability of motorists to make decisions, driver expectations, decision and reaction time, conformance to natural paths of movement, pedestrian use and habits, bicycle use and habits.
- Traffic Considerations - design and actual capacities, design-hour turning movements, size and operating characteristics of vehicle, variety of movements (diverging, merging, weaving, and crossing), vehicle speeds, transit involvement, crash experience, bicycle movements, pedestrian movements.
- Physical Elements - character and use of abutting property, horizontal and vertical alignments at the intersection, sight distance, angle of the intersection, conflict area, speed-change lanes, geometric-design features, traffic control devices, lighting equipment, safety features, bicycle traffic, environmental factors, cross walks, parking, directional signing and marking.
- Economic Factors - cost of improvements, effects of controlling or limiting rights-of-way on abutting residential or commercial properties where channelization restricts or prohibits vehicular movements, energy consumption.
- Functional Intersection Area - boundary (much larger than the physical intersection; includes perception-reaction distance, maneuver distance, deceleration distance and queue-storage distance), access points.
GDOT Design Policy Manual ver. 2.0 Revised 6/1/2007
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