A Predictive Approach to Identify Geometrically Hazardous Road Segments and Evaluate the Relative Safety Effects of Design Alternatives

Alamirew Mulugeta Tola,Tamene Adugna Demissie,Fokke Saathoff,Alemayehu Gebissa

doi:10.3390/su14053026

Abstract

This study has two goals: First, to fill a gap in the use of the predictive approach for evaluating road safety performance in Ethiopia, the most recent analytical methods of the HSM predictive approach in IHSDM software were used to evaluate the safety and operational effects of the existing roadway geometric design. Second, to assure safety and a sustainable transportation system, the relative safety effects of design changes made to hazardous road segments were quantified. Based on the Crash Prediction Module (CPM) evaluation of IHSDM software, the study identified fifteen hazardous road segments on the existing rural two-lane roads of Addis Ababa to Chacha and Addis Ababa to Dillela. The design changes made to the hazardous road segments have resulted in a remarkable reduction in crash rate, especially on the first top five hazardous segments, where incredible improvements have been observed. The total safety benefits acquired by applying engineering mitigations to the fifteen identified hazardous segments are described as follows: 17.18% reduction in total crash frequency (crashes/year), 58.94% reduction in crash rate (crashes/km/year), and 58.86% reduction in travel crash rate (crashes/million veh-km). In general, the study’s findings underlined the effectiveness of performance-based road safety evaluation and design in providing safe, efficient, and economically-feasible roadway infrastructure. The IHSDM reports and graphical outputs assist decision-making in the roadway design process by providing a quantitative evaluation of the safety impact of various design features and identifying roadway segments with safety concerns. Additionally, IHSDM is a tool capable of saving time for Road Safety Audit (RSA) teams. The paper also outlined the need for a computerized crash database recording system in Ethiopia to develop jurisdiction-specific Safety Performance Functions (SPFs).

Highlights

Improving the safety of road infrastructure is one of the primary goals of transportation engineering
The Safety Performance Functions (SPFs) model developed by Highway Safety Manual (HSM) for the undivided rural two-way two-lane road is only applicable to roads with a maximum average daily traffic (AADT) of 17,800 vpd
Safety evaluations based on road safety performance estimates (i.e., Crash Prediction Module (CPM) evaluation) are an effective technique for identifying inconsistencies in a roadway network as well as quantifying the relative safety performance of design alternatives

Summary

Introduction

Improving the safety of road infrastructure is one of the primary goals of transportation engineering. The process of identifying hazardous road locations ( called blackspots, high-risk locations, hotspots, crash-prone zones, inconsistent, etc.) is defined as the process by which a road network is screened to detect places that require safety inquiries [2]. It has a long history in traffic engineering and is considered the primary. Road locations with a higher number of crashes than other similar locations due to local risk factors are considered hazardous or high-risk locations [6] This means that high-risk locations are places where the geometric design and traffic circumstances have a major impact on the crash occurrence and can be mitigated using engineering remedies. The list of hazardous sites is prioritized for additional engineering research [3], and the most cost-effective projects are frequently selected to obtain the best outcomes with limited funds [5,7]

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Conclusion