Procedures for Setting Advisory Speeds on Curves

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U.S. Department of Transportation
Federal Highway Administration

June 2011

FHWA-SA-11-22

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Curve Advisory Software (CAS)
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Disclaimer

The contents of this handbook reflect the views of the authors, who are responsible for the facts and the accuracy of the data published herein. The contents do not necessarily reflect the official view or policies of the Federal Highway Administration (FHWA). This handbook does not constitute a standard, specification, or regulation. It is not intended for construction, bidding, or permit purposes. The engineer in charge of the project was Robert Milstead, P.E. #17172 (Maryland).

Notice

The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this handbook.

Acknowledgements

The report that led to the development of this handbook was sponsored by the Texas Department of Transportation and the Federal Highway Administration. The research report was written by Dr. James Bonneson, Mr. Michael Pratt, Mr. Jeff Miles, and Dr. Paul Carlson (1). These researchers are employees with the Texas Transportation Institute (TTI).



Table of Contents

Technical Report Documentation Page
Chapter 1. Introduction
empty cell 1.1 Overview
empty cell 1.2 Purpose And Scope
Chapter 2. Conveying Changes In Horizontal Alignment
empty cell 2.1 Overview
empty cell 2.2 Horizontal Curve Safety And Operation
empty cell 2.3 Warning Signs For Changes In Horizontal Alignment
empty cell 2.4 Curve Advisory Speed Software
Chapter 3. Methods For Establishing Advisory Speed
empty cell 3.1 Overview
empty cell 3.2 Direct Method
empty cell 3.3 Compass Method
empty cell 3.4 GPS Method
empty cell 3.5 Design Method
empty cell 3.6 Ball-Bank Indicator Method
empty cell 3.7 Accelerometer Method
empty cell 3.8 Confirming Speed For Conditions
empty cell 3.9 Workshops And Webinars
empty cell 3.10 Summary
Chapter 4. Curve Signing Guidelines
empty cell 4.1 Overview
empty cell 4.2 Guidelines
References


List of Tables

Table 1. Comparison of the Six Methods for Establishing Curve Advisory Speeds


List of Figures

Figure 1 – Effect of Radius, Tangent Speed, and Vehicle Type on Curve Speed
Figure 2 – Curve Crash Rate as a Function of Radius
Figure 3 – Horizontal Alignment Signs and Plaques (MUTCD 2009 Edition)
Figure 4 – Curve Advisory Speed (CAS) Software Analysis Worksheet
Figure 5 – Location of Critical Portion of Curve
Figure 6 – Curve Advisory Speed (CAS) Software Input Data
Figure 7 – Curve Advisory Speed (CAS) Software Advisory Speed Calculation
Figure 8 – Effect of Lateral Shift on Travel Path Radius
Figure 9 – GPS Method Equipment Setup in Test Vehicle
Figure 10 – Texas Roadway Analysis and Measurement Software (TRAMS) Main Panel
Figure 11 – Import TRAMS Data
Figure 12 – Ball-Bank Indicator
Figure 13 – CurveRite Front Panel
Figure 14 – CurveRite Measurement
Figure 15 – MUTCD 2009 Edition Criteria for the Selection of Horizontal Alignment Sign
Figure 16 – MUTCD 2009 Edition Criteria for the Typical Spacing of Chevron Alignment Signs on Horizontal Curves
Figure 17 – MUTCD 2009 Edition Criteria for Advance Placement of Warning Signs
Figure 18 – Curve Advisory Speed (CAS) Software Traffic Control Device Guidance


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