Date of Award

12-2024

Degree Name

Master of Science in Engineering

Department

Civil and Construction Engineering

First Advisor

Valerian Kwigizile, Ph.D.

Second Advisor

Jun-Seok Oh, Ph.D.

Third Advisor

Hexu Liu, Ph.D.

Keywords

Design guidelines, Extreme Value Theory, pedestrian safety, roundabouts, slip lanes, surrogate safety measures

Access Setting

Masters Thesis-Open Access

Abstract

The implementation of slip lanes at roundabouts has been widely adopted to improve traffic flow and reduce vehicle conflicts. However, the presence of slip lanes introduces significant risks for pedestrians, influencing vehicle speeds, merging behaviors, and increasing the potential for pedestrian-vehicle conflicts. This study investigates pedestrian safety at roundabouts with various slip lane designs, focusing on their impact on vehicle speeds, pedestrian-vehicle conflicts, and yielding behavior. Also, the study evaluates commonly used surrogate safety measures by employing extreme value models to assess their efficiency.

The study addresses two primary objectives: (1) analyzing the effects of different slip lane configurations on pedestrian safety, and (2) evaluating the suitability of surrogate safety measures in assessing pedestrian conflicts. To achieve these objectives, the research incorporated a multi-faceted approach: reviewing existing slip lane design guidelines, simulating pedestrian-vehicle interactions using VISSIM, applying the Surrogate Safety Assessment Model (SSAM) to quantify simulated conflicts, and employing Extreme Value Theory (EVT) to evaluate surrogate safety indicators.

Findings indicate that unchanneled lanes provide the safest environment for pedestrians, recording the lowest vehicle speeds and conflict rates. Yield-control slip lanes strike a balance between pedestrian safety and traffic flow by moderating vehicle speeds and promoting yielding behavior. Conversely, free-flow slip lanes, while optimizing vehicular efficiency, exhibit the highest speeds and conflict rates, particularly at entry points, increasing pedestrian risks. Among the surrogate safety indicators analyzed, Post Encroachment Time (PET) emerged as the most effective for assessing pedestrian-vehicle conflicts. These findings support the development of context-sensitive slip lane guidelines, contributing to enhanced pedestrian safety and efficient traffic management at roundabouts.

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