Innovative Intersections and Interchanges

 

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Continuous Green-T (CGT) icon
Innovative Intersection: Continuous Green-T (CGT)
U.S. 40 (Columbia Pike) at Rivers Edge Road, Columbia, Md.

A CGT is also known as:

  • Turbo-T
  • High-T
  • Seagull

What Is A CGT?

  • Intersection design where one major street direction of travel (the top side of the “T”) can pass through the intersection without stopping, and the opposite major street direction of travel is typically controlled by a traffic signal
  • Left-turn vehicles from the side street use a channelized receiving lane on the major street to merge onto the major street
  • Intersection is typically signalized but can also be designed without a traffic signal

When Should It Be Considered?

  • At intersections:
    • With three legs
    • With heavy through traffic volumes on the major street
    • With moderate to low left-turn traffic volumes on the side street
    • Where there are no driveways along the major street opposite the side street
    • With a limited number of pedestrian crossings across the major street or with an alternative pedestrian crossing location nearby

Benefits

  • Improved safety: Channelizing left-turn vehicles from the side street reduces the potential for angle crashes
  • Increased efficiency: One direction of travel on the major street is free-flow, and, as a result, more green time can be provided to the other movements, reducing delay
  • Free-flow in one direction: One direction of travel on the major street never stops, which improves traffic signal synchronization and reduces corridor travel times

How to Navigate

Below shows how to navigate a CGT intersection. Click the image to view a larger version or watch the video.

CGT navigation diagram

Conflict Points

The number of conflict points (locations where vehicle travel paths intersect) is one metric that can be used to evaluate the safety of an innovative intersection or interchange.

There are three categories: crossing, merging or diverging.

In general, merging and diverging conflict points — where vehicles are moving in the same direction — are associated with less severe crash types than crossing conflict points where vehicles are moving in opposite directions.

The diagrams below compare the possible vehicle travel movements and associated conflict points at a conventional three-leg intersection to a CGT.

These diagrams represent a general case, with one travel lane in each direction, and do not take into account pedestrian or bicycle movements at an intersection or interchange.

When compared to a conventional three-leg intersection, a CGT has the same number and types of conflict points.

Conventional Intersection: Conflict Points

Conflict Point

CGT: Conflict Points

Conflict Point

Resources

Virginia Department of Transportation

Federal Highway Administration

Page last modified: Nov. 7, 2019