Study Details

Study Title: Safety Effects of Low-Cost Systemic Safety Improvements at Signalized and Stop-Controlled Intersections

Authors: Le et al.

Publication Date: JAN, 2017

Abstract: Packages of intersection treatments, including signing, pavement marking and signal 2 enhancements, were installed at many signalized and stop-controlled intersections in South Carolina. This study evaluated the overall safety effectiveness of the concurrent implementation of these systemic low-cost treatments as part of the FHWA Evaluation of Low Cost Safety Improvements Transportation Pooled Fund. The dataset included both urban and rural 3-legged and 4-legged intersections with two or four lanes on the major road. The study employed an empirical Bayes (EB) before-after analysis. The aggregate results indicate reductions for all crash types analyzed in this study. For signalized intersections, the crash modification factors (CMF) are 0.955, 0.893, 0.974, 0.883, and 0.969 for total, fatal and injury, rear-end, right-angle, and nighttime crashes, respectively. The CMFs for fatal and injury and right-angle crashes are statistically significant at 95-percent and the CMF for total crashes is statistically significant at 90-percent confidence levels. For stop controlled intersections, the CMFs are 0.917, 0.899, 13 0.933, 0.941 and 0.853 for total, fatal and injury, rear-end, right-angle, and nighttime crashes, respectively. All CMFs for stop-controlled intersections are statistically significant at the 95-percent confidence level. An economic analysis shows that systemic, low-cost intersection treatments are cost effective with conservative benefit-cost ratio estimates of 4.1 for total crashes at signalized intersections and 12.4 for total crashes at stop-controlled intersections.

Study Citation: Le, Thanh. Q., F. Gross, and T. Harmon. " Safety Effects of Low-Cost Systemic Safety Improvements at Signalized and Stop-Controlled Intersections". Presented at the 96th Annual Meeting of the Transportation Research Board, Paper No. 17-05379, Washington, D.C., (2017).


CMFs Associated With This Study

Category: Intersection traffic control

Countermeasure: Implement systemic signing and marking improvements at stop-controlled intersections

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.917 8.3 4 Stars All All All All
0.899 10.1 4 Stars All K,A,B,C All All
0.933 6.7 4 Stars Rear end All All All
0.941 5.9 4 Stars Angle All All All
0.853 14.7 4 Stars Nighttime All All All
1.066 -6.6 3 Stars All All All Urban
0.748 25.2 3 Stars All All All Rural
1.095 -9.5 3 Stars All K,A,B,C All Urban
0.734 26.6 3 Stars All K,A,B,C All Rural
1.006 -0.6 3 Stars Rear end All All Urban
0.811 18.9 3 Stars Rear end All All Rural
1.025 -2.5 3 Stars Angle All All Urban
0.833 16.7 3 Stars Angle All All Rural
1.013 -1.3 3 Stars Nighttime All All Urban
0.718 28.2 3 Stars Nighttime All All Rural
0.958 4.2 3 Stars All All All All
0.854 14.6 3 Stars All All All All
0.949 5.1 3 Stars All K,A,B,C All All
0.962 3.8 3 Stars Rear end All All All
0.977 2.3 3 Stars Angle All All All
0.902 9.8 3 Stars Nighttime All All All
0.836 16.4 3 Stars All K,A,B,C All All
0.862 13.8 3 Stars Rear end All All All
0.902 9.8 3 Stars Angle All All All
0.78 22 3 Stars Nighttime All All All
0.879 12.1 3 Stars All All All All
0.814 18.6 3 Stars All K,A,B,C All All
0.919 8.1 3 Stars Rear end All All All
0.925 7.5 3 Stars Angle All All All
0.806 19.4 3 Stars Nighttime All All All
0.96 4 3 Stars All All All All
1.013 -1.3 3 Stars All K,A,B,C All All
0.948 5.2 3 Stars Rear end All All All
0.956 4.4 3 Stars Angle All All All
0.916 8.4 3 Stars Nighttime All All All
0.902 9.8 3 Stars All All All All
0.811 18.9 3 Stars All K,A,B,C All All
0.94 6 3 Stars Rear end All All All
0.99 1 3 Stars Angle All All All
0.828 17.2 3 Stars Nighttime All All All
1.003 -0.3 3 Stars All All All All
1.082 -8.2 3 Stars All K,A,B,C All All
0.982 1.8 3 Stars Rear end All All All
0.97 3 3 Stars Angle All All All
0.979 2.1 3 Stars Nighttime All All All
0.854 14.6 3 Stars All All All All
0.816 18.4 3 Stars All K,A,B,C All All
0.875 12.5 3 Stars Rear end All All All
0.892 10.8 3 Stars Angle All All All
0.779 22.1 3 Stars Nighttime All All All
0.854 14.6 3 Stars All All All All
0.878 12.2 3 Stars All K,A,B,C All All
0.838 16.2 3 Stars Rear end All All All
0.924 7.6 3 Stars Angle All All All
0.78 22 3 Stars Nighttime All All All

Countermeasure: Implement systemic signing and visibility improvements at signalized intersections

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.955 4.5 4 Stars All All All All
0.893 10.7 4 Stars All K,A,B,C All All
0.974 2.6 4 Stars Rear end All All All
0.883 11.7 4 Stars Angle All All All
0.969 3.1 4 Stars Nighttime All All All
0.949 5.1 3 Stars All All All Urban
0.854 14.6 3 Stars All K,A,B,C All Urban
0.96 4 3 Stars Rear end All All Urban
0.884 11.6 3 Stars Angle All All Urban
0.974 2.6 3 Stars Nighttime All All Urban
0.983 1.7 3 Stars All All All Rural
1.054 -5.4 3 Stars All K,A,B,C All Rural
1.06 -6 3 Stars Rear end All All Rural
0.878 12.2 3 Stars Angle All All Rural
0.938 6.2 3 Stars Nighttime All All Rural
0.86 14 3 Stars All All All All
0.81 19 3 Stars All K,A,B,C All All
0.822 17.8 3 Stars Rear end All All All
0.895 10.5 3 Stars Angle All All All
1.044 -4.4 3 Stars Nighttime All All All
0.972 2.8 3 Stars All All All All
0.908 9.2 3 Stars All K,A,B,C All All
1 0 3 Stars Rear end All All All
0.881 11.9 3 Stars Angle All All All
0.955 4.5 3 Stars Nighttime All All All
0.784 21.6 3 Stars All All All All
0.756 24.4 3 Stars All K,A,B,C All All
0.866 13.4 3 Stars Rear end All All All
0.654 34.6 3 Stars Angle All All All
0.884 11.6 3 Stars Nighttime All All All
0.978 2.2 3 Stars All All All All
0.911 8.9 3 Stars All K,A,B,C All All
0.988 1.2 3 Stars Rear end All All All
0.917 8.3 3 Stars Angle All All All
0.98 2 3 Stars Nighttime All All All
0.901 9.9 3 Stars All All All All
0.771 22.9 3 Stars All K,A,B,C All All
0.794 20.6 3 Stars Rear end All All All
1.104 -10.4 3 Stars Angle All All All
0.809 19.1 3 Stars Nighttime All All All
0.846 15.4 3 Stars All All All All
0.819 18.1 3 Stars All K,A,B,C All All
0.829 17.1 3 Stars Rear end All All All
0.833 16.7 3 Stars Angle All All All
1.128 -12.8 3 Stars Nighttime All All All
0.732 26.8 3 Stars All All All All
0.746 25.4 3 Stars All K,A,B,C All All
0.895 10.5 3 Stars Rear end All All All
0.509 49.1 3 Stars Angle All All All
0.914 8.6 3 Stars Angle All All All
0.998 0.2 3 Stars All All All All
0.926 7.4 3 Stars All K,A,B,C All All
1.011 -1.1 3 Stars Rear end All All All
0.928 7.2 3 Stars Angle All All All
0.958 4.2 3 Stars Nighttime All All All