TxDOT Research Library - Publication Details

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Title:

Guidelines for Spacing Between Freeway Ramps

Report No.:

FHWA/TX-10/0-5860-1

Authors:

Kay Fitzpatrick [and five others]

Published:

2010

College Station, Texas

Texas Transportation Institute

Type:

Hard copy + Online document

1 volume (118 pages)

Online Access:

https://library.ctr.utexas.edu/hostedpdfs/tti/0-58...

Access Note:

1.4 MB

Summary

Existing geometric design guidance related to interchange ramp spacing in the Texas Roadway Design Manual and the AASHTO's A Policy on Geometric Design of Highways and Streets (Green Book) is not speed-dependent even though intuition indicates spacing and speed are related. Understanding the relationship between interchange ramp spacing, speed, and freeway operations is important, especially in developing potential design values for higher speeds (e.g., 85 to 100 mph). The objectives of this project were to: (a) investigate relationships between weaving length, speed, and overall vehicle operations on Texas freeways and (b) propose updates to current Texas Department of Transportation guidance on recommended distances between ramps. Within the research tasks several methods were utilized to assist in developing guidance on ramp spacing lengths. The methods or resources used to generate potential lengths included: guidance provided in Design Manual for Roads and Bridges published by the Highways Agency in England, minimum deceleration and acceleration length for freeway conditions, decision sight distance, sign spacing needs, NCHRP project 3-75 findings, findings from field studies at seven study sites, findings from simulation conducted as part of this research, and safety relationships identified in the literature. Suggested ramp spacings were developed for the entrance ramp to exit ramp and exit ramp to exit ramp conditions.

Publ. Place

College Station, Texas

Contents

Chapter 1. Introduction --
Chapter 2. Literature Review (Background; Physical Relationships between Interchange Features; A Historic Look at Ramp Spacing Design Dimensions; Operational Analysis of Interchange Ramps and Ramp Spacing; International Guidance; Minimum Length from Deceleration and Acceleration; Decision Sight Distance; Safety; Sign Spacing for an Exit Ramp) --
Chapter 3. Field Studies (Operational Measures; Data Collection Equipment; Site Identification; Data Collection and Reduction) --
Chapter 4. Simulation (Model Selection; Simulation Test Beds; Initial Simulation Runs; Model Calibration; Simulation of Ramp Spacing Scenarios) --
Chapter 5. Analyze Results --
Chapter 6. Develop Recommendations --
Chapter 7. Summary and Conclusions

Notes

"November 2009; Published: March 2010"
• Project performed in cooperation with the Texas Department of Transportation (TxDOT) and the Federal Highway Administration (FHWA)

Study Number

TxDOT Research Project 0-5860

Study Title

Guidelines for Ramp Terminal Spacing for Freeways

Study Sponsor

Lead University

TTI