Safety Data Analysis to Evaluate Highway Alignment Consistency

Abstract

Road safety has become a priority field worldwide and one of the major factors describing the state of the transport system with its positive and negative changes. Many studies on driver speed behavior can be found in the scientific literature, and researchers have addressed roadway alignment consistency for travel safety in the context of real operating speeds. This study illustrates an experimental analysis conducted on the Tirrenia Inferiore State Highway in southern Italy without spiral transition curves between geometric tangent and circular elements on the horizontal alignment in order to check a new prediction consistency model. Two consistency measures were developed and compared with the results available in the literature: the first was the relative area bounded by the speed profile and the average weighted speed, and the second was the standard deviation of operating speeds in each design element along the entire road examined. With a combination of these two previous measures and according to an extensive sensitivity analysis, a consistency model was developed and thresholds for good, acceptable, and poor road consistency can now be proposed. The consistency prediction model was related to the number of crashes occurring between 2003 and 2010. It was found that as design consistency increased, the number of crashes decreased significantly. The consistency model can be used for this purpose during the geometric design process or during the evaluation process for two-lane rural highways

Using Decision Trees for Comparing Different Consistency Models

“…Many authors agree that operating speed is the form most commonly used to evaluate consistency, as it reflects driver behavior (Gibreel et al, 1999;Fitzpatrick et al 2000;Ng and Sayed, 2004;Camacho-Torregosa et al, 2013). Operating speed is the most representative parameter of real driving performance (Dell`Acqua et al, 2013). The operating speed is defined as the 85th percentile of the distribution (V 85 ) of speeds by drivers under free-flow conditions on a particular location of the road alignment (Bella, 2007).…”

Investigation of Asphalt Texture Roughness on Friction Evolution for Wheeled Vehicles

“…This approach is in line with methodologies presented by (Dell' Acqua et al 2013, Cafiso, Di Graziano 2012Dreyer 2014;Misra, Das 2003). We repeated our experiments 5 times, all results reported are averaged over those 5 independent experiments.…”

A Novel Approach for Operating Speed Continuous Predication Based on Alignment Space Comprehensive Index

“…Moreover, for the positive and negative grade, the corresponding has a different value range. Consequently, the vertical ACI model (see (2)) is developed based on the improvements of the linear regression equation.…”

“…Furthermore, the 3 statistical criterion [2] was used to check the homogeneity distribution around the mean and the maximum deviation of speed distribution equal to 3 . Consequently, speed data from more than 2400 points were measured.…”

“…This designing method is prone to be inconsistent with successive elements of a road. Large amount of practical studies highlights the fact that inconsistent alignment might cause a sudden change in the characteristics of the roadway, which would lead to critical driving errors and crash risks [1,2]. A consistent alignment design is required to meet drivers' expectations and promotes harmonious driving behaviors.…”