Study Details

Study Title: Safety Performance Functions for Low-Volume Roads

Authors: Acqua and Russo

Publication Date: NOV, 2010

Abstract: This paper analyzes roadway safety conditions using the network approach for a number of Italian roadways within the Province of Salerno. These roadways are characterized by low-volume conditions with a traffic flow of under 1,000 vehicles per day and they are situated partly on flat/rolling terrain covering 231.98 kilometers and partly on mountainous terrain for 751.60 kilometers. Since 2003, the Department of Transportation Engineering at the University of Naples has been conducting a large-scale research program based on crash data collected in Southern Italy. The research-study presented here has been used to calibrate crash prediction models (CPMs) per kilometer per year. The coefficients of the CPMs are estimated using a non-linear multi-variable regression analysis utilizing the least-square method. In conclusion, two injurious crash prediction models were performed for two-lane rural roads located on flat/rolling area with a vertical grade of less than 6 percent and on mountainous terrain with a vertical grade of more than 6 percent. A residuals analysis was subsequently developed to assess the adjusted coefficient of determination and p-value for each assessible coefficient of the prediction model. CPMs are a useful tool for estimating the expected number of crashes occurring within the roads' geometric components (intersections and road sections) as a function of infrastructural, environmental, and roadway features. Several procedures exist in the scientific literature to predict the number of crashes per kilometer per year. CPMs can also be used as a tool for safety improvement project prioritization.

Study Citation: Acqua, G. D. and F. Russo., "Safety Performance Functions for Low-Volume Roads." Presented at the 90th Annual Meeting of the Transportation Research Board, Washington, D.C., (2011).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Alignment

Countermeasure: Change horizontal alignment

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 2 Stars All K,A,B,C Not Specified Rural

Countermeasure: Change vertical grade

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 2 Stars All K,A,B,C Not Specified Rural
CMF Equation CRF Equation 3 Stars All K,A,B,C Not Specified Rural

Category:Roadway

Countermeasure: Increase roadway width (lanes and shoulders in meters)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 2 Stars All K,A,B,C Not Specified Rural
CMF Equation CRF Equation 3 Stars All K,A,B,C Not Specified Rural

Category:Speed management

Countermeasure: Change mean speed (km/hr)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
CMF Equation CRF Equation 3 Stars All K,A,B,C Not Specified Rural
CMF Equation CRF Equation 2 Stars All K,A,B,C Not Specified Rural