Existing geometric design guidance related to interchange ramp spacing in the Texas Roadway Design Manual and AASHTO's Policy on Geometric Design of Highways and Streets is not speed dependent even though intuition indicates that 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 Texas Department of Transportation project were (a) to investigate relationships between weaving length, speed, and overall vehicle operations for successive ramps on Texas freeways and (b) to propose updates to current guidance on recommended distances between ramps. Several methods were used to assist in developing guidance on ramp spacing lengths. The methods and resources used to generate potential lengths included (a) guidance provided in the Design Manual for Roads and Bridges published by the Highways Agency in England, (b) minimum deceleration and acceleration lengths for freeway conditions, (c) decision sight distance, (d) sign spacing needs, (e) NCHRP Project 3–75 findings, (f) findings from field studies at seven sites in Texas, (g) findings from simulation conducted as part of this research, and (h) safety relationships identified in the literature. Suggested ramp spacings were developed for the entrance–exit and exit–exit ramp scenarios.


    Access

    Download

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Guidelines for Spacing between Freeway Ramps


    Additional title:

    Transportation Research Record: Journal of the Transportation Research Board


    Contributors:


    Publication date :

    2011-01-01




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English



    Guidelines for Spacing Between Freeway Ramps

    K. Fitzpatrick / R. J. Porter / G. Pesti et al. | NTIS | 2010



    Urban Freeway On-Ramps

    Yi, Hanwen / Mulinazzi, Thomas E. | Transportation Research Record | 2007


    Microscopic Safety Evaluation and Prediction for Freeway-to-Freeway Interchange Ramps

    Wang, Ling / Abdel-Aty, Mohamed | Transportation Research Record | 2016


    Effects of Off-Ramps on Freeway Operation

    W. E. Tipton / J. D. Carvell / C. Pinnell | NTIS | 1965