Improving Intersection Design Practices -- Final
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Kentucky Transportation Center Research Report KTC -10-09/SPR 380-09-1F Improving Intersection Design Practices FINAL REPORT – PHASE I Our Mission We provide services to the transportation community through research, technology transfer and education. We create and participate in partnerships to promote safe and effective transportation systems. © 2012 University of Kentucky, Kentucky Transportation Center Information may not be used, reproduced, or republished without our written consent. Kentucky Transportation Center 176 Oliver H. Raymond Building Lexington, KY 40506-0281 (859) 257-5028 fax (859) 257-1815 www.ktc.uky.edu Research Report KTC-10-09 / SPR-380-09-1F IMPROVING INTERSECTION DESIGN PRACTICES Final Report – Phase I by Nikiforos Stamatiadis Professor and Adam Kirk Research Engineer Department of Civil Engineering and Kentucky Transportation Center College of Engineering University of Kentucky Lexington, Kentucky The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views of policies of the University of Kentucky, the Kentucky Transportation Cabinet, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacture names and trade names is for identification purposes and is not to be considered an endorsement. June 2010 1. Report Number 2. Government Accession No. 3. Recipient’s Catalog No. KTC-10-09 / SPR-380-09-1F 4. Title and Subtitle 5. Report Date June 2010 Improving Intersection Design Practices 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. N. Stamatiadis and A. Kirk KTC-10-09 / SPR09-380-1F 9. Performing Organization Name and Address 10. Work Unit No. Kentucky Transportation Center College of Engineering University of Kentucky 11. Contract or Grant No. Lexington, Kentucky 40506-0281 SPR316 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered: Final Draft; 07/08 – 06/10 Kentucky Transportation Cabinet 200 Mero Street 14. Sponsoring Agency Code Frankfort, KY 15. Supplementary Notes 16. Abstract The purpose of this report is to document the development of the Intersection Design Alternative Tool (IDAT) developed for the Kentucky Transportation Cabinet. IDAT provides an automated objective design and evaluation approach of 14 alternative intersection designs to assist in the conceptual design of at-grade intersections. The tool evaluates intersection operations, safety performance, bicycle/pedestrian accommodation and has the ability to assist access management implementation. 17. Key Words 18. Distribution Statement Intersection Design, Roundabout, Inside left-turn, median Unlimited u-turn, superstreet, continuous flow, jughandle, bowtie, intersection evaluation i 19. Security Classification (report) 20. Security Classification (this 21. No. of Pg: 79 22. Price $0 Unclassified page) TABLE OF CONTENTS Executive Summary ..................................................................................................................... iv INTRODUCTION .......................................................................................................................... 1 Problem Statement ........................................................................................................ 1 Research Objectives and Approach .............................................................................. 1 Report Organization ...................................................................................................... 3 LITERATURE REVIEW ................................................................................................................ 4 Introduction .................................................................................................................... 4 Alternative Intersection Designs .................................................................................... 4 Intersection Design Factors ........................................................................................... 7 Intersection Design Procedures .................................................................................. 13 Intersection Safety Issues ........................................................................................... 15 Summary ..................................................................................................................... 22 RESEARCH FINDINGS .............................................................................................................. 25 Evaluation Approach ................................................................................................... 28 Simulation Results ....................................................................................................... 31 Intersection Design Evaluation Tool ............................................................................ 36 CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 42 Recommendations ....................................................................................................... 42 Phase II Work Plan ...................................................................................................... 42 Task 2 .......................................................................................................................... 42 Task 3 .......................................................................................................................... 43 REFERENCES ........................................................................................................................... 44 Appendix A .................................................................................................................................. 47 Appendix B .................................................................................................................................. 60 Appendix C ................................................................................................................................. 70 LIST OF TABLES Table 1 Level of service and maximum sum of critical lane volumes at signalized intersections14 Table 2 Level of service criteria for unsignalized intersections……………………………………15 Table 3 Intersection approach volumes………………………………………………………………29 Table 4 North-south turn percentages.……………………………………………………………….29 Table 5 Critical volume capacity thresholds………………………………………………………….36 ii Table 6 Proposed intersection design evalaution tool………..…………………………………… . 40 LIST OF FIGURES Figure 1 Signalized intersection delay and critical volume…………………………………………32 Figure 2 All way stop control intersection delay and critical volume ……………………...………33 Figure 3 Two-way stop control intersection delay and approach critical volume……………...…34 Figure 4 Roundabout approach delay and approach and conflicting volume…………………….35 Figure 5 Example Design Tool Output ……………………………………………………………….41 iii EXECUTIVE SUMMARY Intersections are a critical component of the roadway system and frequently act as choke points on the transportation system. In addition, intersection crashes account for approximately 30 percent of all crashes in Kentucky (Kentucky State Police, 2007). As a critical component of the state transportation system, intersection design requires an objective methodology to identify the most appropriate solution that meets the purpose and need of the project as well as addresses site constraints. The current state of practice, while achieving great strides in improving the efficiency of Kentucky’s roadway system, lacks a systematic, objective and well defined approach to evaluating individual design alternatives. The goal of this project is to improve intersection design practices by 1) expanding the scope of intersection design alternatives considered and 2) providing a structured and objective evaluation process to compare alternative design concepts. This is achieved through the development of the Intersection Design Alternative Tool (IDAT) that is capable of evaluating 14 alternative traffic control and intersection conceptual designs for a given location. IDAT evaluates intersection operations, safety performance, bicycle/pedestrian accommodation and the ability to assist access management implementation. A major component of this effort was the development of methods to size different intersection designs. IDAT identifies the most efficient design (minimum number of lanes) that is capable of meeting a targeted level of operation. As such, the design team will be presented with several options, which meet the minimum operational requirements, allowing examination of other trade-offs such as right of way impacts, safety considerations etc. This approach will eliminate the need to compare different alternatives with varying performance levels across different types of traffic control measures. The software developed as part of this Phase I of the study is ready to be distributed for use to the practitioners. The software allows for the preliminary evaluation of all intersection designs considered and provides a basic method for comparing all of them at an equal level of operation. Recommendations for Phase II are also provided which seek to develop a more robust safety evaluation method for at-grade intersections. IDAT provides greater efficiency in the evaluation and design of intersection alternatives and