Study Details

Study Title: Evaluation of the Safety Effectiveness of Selected Treatments at Urban Signalized Intersections

Authors: Srinivasan et al.

Publication Date: JAN, 2008

Abstract: This study conducted a before-after evaluation using the empirical Bayes methodology for four types of reatments at signalized intersections using data from Winston-Salem, North Carolina. The results indicated that changing to protected left-turn phasing from permissive or permissive/protected phasing can lead to a virtual elimination of left-turn crashes, but other crashes, which are likely to be less severe, can increase. Conversion from night-time flash back to regular phasing seems effective in reducing night-time crashes. Replacing 8 inch signal heads with 12 inch heads seems effective in reducing right-angle crashes, but this measure can increase other, less severe crashes. Adding an additional red signal lens to an existing one, or changing from permissive to permissive/protected left turn phasing did not seem very effective in reducing crashes, but these results are not definitive since they were based on the limited number of sites. Further research is needed using data from other jurisdictions, so that more definitive conclusions can be made regarding the safety effectiveness of these treatments.

Study Citation: Srinivasan, R., F. Council, C. Lyon, F. Gross, N. Lefler, and B. Persaud. "Evaluation of the Safety Effectiveness of Selected Treatments at Urban Signalized Intersections." TRB 87th Annual Meeting Compendium of Papers CD-ROM. Washington, D.C., 2008.


CMFs Associated With This Study

Category: Intersection traffic control

Countermeasure: Change permitted to protected/permitted or permitted/protected

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.045 -4.5 4 Stars All All Not Specified Urban

Countermeasure: Install dual red signal lenses

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.05 -5 4 Stars Angle All Not Specified
1.18 -18 4 Stars All All Not Specified

Countermeasure: Protected/permissive to protected-only left turn phasing

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0 100 4 Stars Angle All Not Specified
0 100 4 Stars Angle All Not Specified
1.02 -2 4 Stars All All Not Specified

Countermeasure: Replace 8-inch red signal heads with 12-inch

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.58 42 5 Stars Angle All Not Specified
0.97 3 4 Stars All All Not Specified

Countermeasure: Replace permissive with protected

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.021 97.9 4 Stars Angle All Not Specified Urban
0.975 2.5 4 Stars All All Not Specified Urban