An Investigation of the Safety Performance of Roundabouts in Korea Based on a Random Parameters Count Model

Minho Park,Je-Jin Park,Dongmin Lee

doi:10.1155/2018/5628293

Abstract

It is well known that a roundabout is an efficient and safe intersection. However, the safety is generally influenced by the given various conditions. This study analyzed the effects of the geometric and traffic flow conditions on traffic accident frequency at roundabouts, constructed in Korea since 2010. Many previous studies have investigated the efficiency and safety effects of roundabout installation. However, not many studies have analyzed the specific influences of individual geometric elements and traffic flow conditions of roundabouts. Accordingly, this study analyzed the effects of various influencing variables on traffic accident frequency based on a random parameter count model using traffic accident data in 199 roundabouts. Using random parameters that can take into account unobserved heterogeneity, this study tried to make up for the weakness of the fixed parameters model, which constrains estimated parameters to be fixed across all observations. A total of eight variables were determined to be the main influencing factors on traffic accident frequency including the number and width of entry lanes, the presence of pedestrian crossings, the width of the circulatory lanes, the presence of central islands, the radius and number of entry lanes, and traffic volume influence accident frequency. Based on the study results, safer roundabout design and more efficient roundabout operation are expected.

Highlights

A roundabout is a circular intersection in which traffic travels circulating around a central island and the entering traffic must yield to circulating traffic
A total of 199 roundabouts were utilized to construct the traffic accident frequency model that can be applied with the random parameters count model
The main variables used to develop the model were, region types(urban and rural area), type of intersection, the curvature radius for each entry lane, the number of lanes, width of the entry lane to the roundabouts, lane width at the exit lane, presence of pedestrian crosswalks, distance between the yield line and pedestrian crosswalk, presence of a central island, presence of a vertical grade, channelization, traffic volumes, inscribed circle diameter, diameter of the central island, number of circulatory lanes, and width of circulatory lanes

Summary

Introduction

A (modern) roundabout is a circular intersection in which traffic travels circulating around a central island and the entering traffic must yield to circulating traffic. The changed driving rule at a roundabout is that entering traffic must yield to circulating traffic. Through this driving rule change, the operation and safety of roundabouts have improved compared to signalized intersections as well as rotaries. Some previous studies explained that roundabouts can improve efficiency and safety performance comparing other type of intersections and, roundabouts can reduce conflict points at intersections and accident severity significantly [1,2,3,4,5,6]. Researches have shown that if existing signalized intersections are changed to roundabouts, the traffic accident frequency and severity can be reduced [8,9,10,11,12,13,14]

Methods

Results

Conclusion