At-grade intersection

At-grade intersection is a type of road intersection where two or more roads meet at the same level. This is in contrast to grade-separated intersections, where roads cross at different levels (e.g., one or more roads passing over or under others).

Overview

At-grade intersections are common in both urban and rural settings. They can be controlled by traffic signals, stop signs, or left uncontrolled. The design and control of at-grade intersections can significantly impact traffic flow, road safety, and the environment.

Types of At-grade Intersections

There are several types of at-grade intersections, including:

• Crossroads: A junction where four roads meet at right angles.
• T-junction: A junction where three roads meet, and one road ends.
• Y-junction: A junction where three roads meet, but not at right angles.
• Roundabout: A circular intersection where traffic flows around a central island.
• Traffic circle: A type of intersection where traffic passes in one direction around a central island.

Design Considerations

The design of at-grade intersections involves several considerations, including:

• Traffic volume: The amount of traffic that will use the intersection.
• Road geometry: The layout and alignment of the roads.
• Sight distance: The distance a driver can see to safely navigate the intersection.
• Traffic control devices: The use of signs, signals, and markings to control traffic.

Safety and Efficiency

At-grade intersections can present safety and efficiency challenges. High traffic volumes, poor visibility, and complex navigation can lead to traffic congestion and traffic collisions. However, well-designed at-grade intersections can facilitate smooth traffic flow and improve road safety.

See Also

• Grade separation
• Interchange (road)
• Traffic engineering (transportation)