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
0.956	4.4		Angle	All	All	All

0.916	8.4		Nighttime	All	All	All

0.902	9.8		All	All	All	All

0.811	18.9		All	K,A,B,C	All	All

0.94	6		Rear end	All	All	All

0.99	1		Angle	All	All	All

0.828	17.2		Nighttime	All	All	All

1.003	-0.3		All	All	All	All

1.082	-8.2		All	K,A,B,C	All	All

0.982	1.8		Rear end	All	All	All

0.97	3		Angle	All	All	All

0.979	2.1		Nighttime	All	All	All

0.854	14.6		All	All	All	All

0.816	18.4		All	K,A,B,C	All	All

0.875	12.5		Rear end	All	All	All

0.892	10.8		Angle	All	All	All

0.779	22.1		Nighttime	All	All	All

0.854	14.6		All	All	All	All

0.878	12.2		All	K,A,B,C	All	All

0.838	16.2		Rear end	All	All	All

0.924	7.6		Angle	All	All	All

0.78	22		Nighttime	All	All	All

0.917	8.3		All	All	All	All

0.899	10.1		All	K,A,B,C	All	All

0.933	6.7		Rear end	All	All	All

0.941	5.9		Angle	All	All	All

0.853	14.7		Nighttime	All	All	All

1.066	-6.6		All	All	All	Urban

0.748	25.2		All	All	All	Rural

1.095	-9.5		All	K,A,B,C	All	Urban

0.734	26.6		All	K,A,B,C	All	Rural

1.006	-0.6		Rear end	All	All	Urban

0.811	18.9		Rear end	All	All	Rural

1.025	-2.5		Angle	All	All	Urban

0.833	16.7		Angle	All	All	Rural

1.013	-1.3		Nighttime	All	All	Urban

0.718	28.2		Nighttime	All	All	Rural

0.958	4.2		All	All	All	All

0.854	14.6		All	All	All	All

0.949	5.1		All	K,A,B,C	All	All

0.962	3.8		Rear end	All	All	All

0.977	2.3		Angle	All	All	All

0.902	9.8		Nighttime	All	All	All

0.836	16.4		All	K,A,B,C	All	All

0.862	13.8		Rear end	All	All	All

0.902	9.8		Angle	All	All	All

0.78	22		Nighttime	All	All	All

0.879	12.1		All	All	All	All

0.814	18.6		All	K,A,B,C	All	All

0.919	8.1		Rear end	All	All	All

0.925	7.5		Angle	All	All	All

0.806	19.4		Nighttime	All	All	All

0.96	4		All	All	All	All

1.013	-1.3		All	K,A,B,C	All	All

0.948	5.2		Rear end	All	All	All

Countermeasure: Implement systemic signing and visibility improvements at signalized intersections

CMF	CRF(%)	Quality	Crash Type	Crash Severity	Roadway Type	Area Type
1.011	-1.1		Rear end	All	All	All

0.928	7.2		Angle	All	All	All

0.958	4.2		Nighttime	All	All	All

0.878	12.2		Angle	All	All	Rural

0.938	6.2		Nighttime	All	All	Rural

0.86	14		All	All	All	All

0.81	19		All	K,A,B,C	All	All

0.822	17.8		Rear end	All	All	All

0.895	10.5		Angle	All	All	All

1.044	-4.4		Nighttime	All	All	All

0.972	2.8		All	All	All	All

0.908	9.2		All	K,A,B,C	All	All

1	0		Rear end	All	All	All

0.881	11.9		Angle	All	All	All

0.955	4.5		Nighttime	All	All	All

0.784	21.6		All	All	All	All

0.756	24.4		All	K,A,B,C	All	All

0.866	13.4		Rear end	All	All	All

0.654	34.6		Angle	All	All	All

0.884	11.6		Nighttime	All	All	All

0.978	2.2		All	All	All	All

0.911	8.9		All	K,A,B,C	All	All

0.988	1.2		Rear end	All	All	All

0.917	8.3		Angle	All	All	All

0.98	2		Nighttime	All	All	All

0.901	9.9		All	All	All	All

0.771	22.9		All	K,A,B,C	All	All

0.794	20.6		Rear end	All	All	All

1.104	-10.4		Angle	All	All	All

0.809	19.1		Nighttime	All	All	All

0.846	15.4		All	All	All	All

0.819	18.1		All	K,A,B,C	All	All

0.829	17.1		Rear end	All	All	All

0.833	16.7		Angle	All	All	All

1.128	-12.8		Nighttime	All	All	All

0.732	26.8		All	All	All	All

0.746	25.4		All	K,A,B,C	All	All

0.895	10.5		Rear end	All	All	All

0.509	49.1		Angle	All	All	All

0.914	8.6		Angle	All	All	All

0.998	0.2		All	All	All	All

0.926	7.4		All	K,A,B,C	All	All

0.955	4.5		All	All	All	All

0.893	10.7		All	K,A,B,C	All	All

0.974	2.6		Rear end	All	All	All

0.883	11.7		Angle	All	All	All

0.969	3.1		Nighttime	All	All	All

0.949	5.1		All	All	All	Urban

0.854	14.6		All	K,A,B,C	All	Urban

0.96	4		Rear end	All	All	Urban

0.884	11.6		Angle	All	All	Urban

0.974	2.6		Nighttime	All	All	Urban

0.983	1.7		All	All	All	Rural

1.054	-5.4		All	K,A,B,C	All	Rural

1.06	-6		Rear end	All	All	Rural

CRASH MODIFICATION FACTORS CLEARINGHOUSE

Study Details

CMFs Associated With This Study

Category: Intersection traffic control