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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
FHWA Highway Safety Programs

Colorado Implements Continuous Green T-Intersections to Reduce the Number of Angle Crashes

Publication Year:

Original publication: Continuous Green T-Intersections (FHWA-SA-09-016) (PDF, 634kB)

Angle crashes are among the most severe crashes that occur at intersections, including “T- intersections,” across the United States. Research has shown that a primary reason for the high number of crashes is driver inability to judge gaps in opposing traffic. The Colorado Department of Transportation (CDOT) was concerned about the high number of crashes at some of its rural T-intersections controlled by traffic signals.

Recognizing that inadequate stopping sight distance can cause crashes, CDOT installed continuous green T-intersection (CGT) at two intersections experiencing a high incidence of crashes, many with injuries. (These existing intersections met minimum Manual on Uniform Traffic Control Devices standards). The CGT design allows main line through traffic to pass through a signalized intersection without stopping while eliminating conflicting left-turning vehicular movement.

"Photograph of a T-intersection where the signal-controlled through tlane at the top of a T-instersection was converted to a continuous green T. Labels indentify the stem of the T and note the addition of a dedicated left turn lane for trafffic seeking to turn left from the stem of the T onto the flat (top) of the T."
Figure 1:   Aerial view of the CGT in Grand Junction, Colorado
Source: Photo from Zane Znamenacek, CDOT (used with permission)

 

 

"Photograph of an intersection that was converted to a continuous green T. Photo is taken from the flat of the T on the approach to the intersection, with the stem to the left. The intersection features a dedicated lane for vehicles turning from the stem onto the flat of the T."
Figure 2:   Westbound on US-160
Photo from David Pickren, CDOT (used with permission).

 

Key Accomplishments

As the CDOT experience demonstrates, CGTs can effectively improve safety and reduce traffic crashes (particularly angle crashes) and their resulting injuries and/or fatalities.

Results

The safety enhancements installed at these Colorado signalized intersections cumulatively reduced total crashes by 60 percent, injury crashes by 70 percent, and angle crashes by 96.8 percent per year.

Contact

Zane Znamenacek
Region 3 Traffic Operations Engineer
Colorado Department of Transportation
Zane.Znamenacek@dot.state.co.us