Safety Index for Evaluation of Two-Lane Rural Highways

The methodological approach to safety evaluation of two-lane rural highway segments that is presented uses both analytical procedures referring to alignment design consistency models and safety inspection processes. A safety index (SI) that quantitatively measures the relative safety performance of a road segment is calculated from the procedure. The SI is formulated by combining three components of risk: the exposure of road users to road hazards, the probability of a vehicle's being involved in an accident, and the resulting consequences should an accident occur. This systematic and replicable procedure integrates two different, complementary approaches–one based on design consistency evaluations and the other on safety inspections–and makes it possible to address a wide variety of safety issues effectively. A further advantage of the procedure is its applicability on highways where crash data are either not available or unreliable. Validation of the procedure was carried out on a sample of roads by a comparison of the risk rank obtained by using the SI and accident history. The SI was assessed in 30 segments chosen from a sample of two-lane rural highways in Italy, and the actual accident situation was obtained with the empirical Bayes (EB) procedure. Spearman's rank correlation was used to determine the level of agreement between the rankings obtained with the two techniques. The results from the Spearman's rank-correlation analysis validate the SI, indicating that the ranking from the SI scores and the EB estimates agrees at the 99.9% level of significance with a correlation coefficient of 0.87.

[1]  Alfonso Montella.  Safety reviews of existing roads: Quantitative safety assessment methodology , 2005 .

[2]  S. Cafiso,et al.  How to Make Two-Lane Rural Roads Safer: Scientific Background and Guide for Practical Application , 2006 .

[3]  Craig Lyon,et al.  Validity of Results from Empirical Bayes Observational Before-After Studies , 2005 .

[4]  Jerry L Graham,et al.  ROADWAY DELINEATION PRACTICES HANDBOOK , 1994 .

[5]  Tarek Sayed,et al.  Development of a Road Safety Risk Index , 2002 .

[6]  Ruediger Lamm,et al.  Safety Evaluation Process for Two-Lane Rural Roads: A 10-Year Review , 2002 .

[7]  Ted R Miller.  BENEFIT-COST ANALYSIS OF LANE MARKING , 1992 .

[8]  Eugene M Wilson,et al.  Practical Safety Tool for Local Low-Volume Rural Roads: The Road Safety Audit Review , 2003 .

[9]  S. Cafiso,et al.  Identification of Hazard Location and Ranking of Measures to Improve Safety on Local Rural Roads , 2007 .

[10]  Hsin-Li Chang,et al.  MODELING THE RELATIONSHIP OF ACCIDENTS TO MILES TRAVELED , 1986 .

[11]  A. O. Abd El Halim,et al.  Analytical Model for Sight Distance Analysis on Three-Dimensional Highway Alignments , 1996 .

[12]  Rune Elvik,et al.  The Handbook of Road Safety Measures , 2009 .

[13]  E Hauer,et al.  SAFETY ANALYSIS OF ROADWAY GEOMETRIC AND ANCILLARY FEATURES , 1996 .

[14]  Grazia La Cava,et al.  A procedure to improve safety inspections effectiveness and reliability on rural two–lane highways , 2006 .

[15]  Kenneth Wade Ogden,et al.  Safer Roads: A Guide to Road Safety Engineering , 1995 .

[16]  Eric R. Green,et al.  DEVELOPMENT OF PROCEDURES FOR IDENTIFYING HIGH-CRASH LOCATIONS AND PRIORITIZING SAFETY IMPROVEMENTS , 2003 .

[17]  S. Cafiso,et al.  Operative Procedures for Road Safety Inspections , 2005 .

[18]  Y. Danieli.  Guide , 2005 .

[19]  Ruediger Lamm,et al.  Highway Design and Traffic Safety Engineering Handbook , 1999 .

[20]  Ezra Hauer,et al.  Estimating Safety by the Empirical Bayes Method: A Tutorial , 2002 .

[21]  Ezra Hauer,et al.  PREDICTION OF THE EXPECTED SAFETY PERFORMANCE OF RURAL TWO-LANE HIGHWAYS , 2000 .

[22]  Poul Greibe,et al.  SIGNING AND MARKING OF SUBSTANDARD HORIZONTAL CURVES ON RURAL ROADS , 1998 .

[23]  J Papi.  GUIDELINES TO BLACK SPOT MANAGEMENT - IDENTIFICATION AND HANDLING , 2002 .

[24]  Ezra Hauer,et al.  OBSERVATIONAL BEFORE-AFTER STUDIES IN ROAD SAFETY -- ESTIMATING THE EFFECT OF HIGHWAY AND TRAFFIC ENGINEERING MEASURES ON ROAD SAFETY , 1997 .

[25]  P Cook,et al.  Practical Road Safety Auditing , 2001 .

[26]  M. Baucus.  Transportation Research Board , 1982 .

[27]  Ezra Hauer,et al.  Estimation of safety at signalized intersections , 1988 .

[28]  S Zein.  Canadian Guide to In-Service Road Safety Reviews , 2004 .

[29]  Paul J Carlson,et al.  Spacing Chevrons on Horizontal Curves , 2005 .