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HIGHWAY DESIGN MANUAL

Chapter 6 - Interchanges

Limited Revision

July 16, 2002

CHANGES TO CHAPTER 6

Pages Change

Multiple Rescind HDM Chapter 6 – Interchanges, with the exception of Section 6.04.09 – Control of Access and related figures.

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Contents Page

6.1 Introduction ...... 6-1

6.2 Control of Access ...... 6-1

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LIST OF FIGURES

6-1 Limits of Fully Controlled Access at Expressway Ramps 6-2 Limits of Fully Controlled Access at Expressway Ramps 6-3 Limits of Fully Controlled Access at Expressway Ramps 6-4 Limits of Fully Controlled Access at Expressway Ramps 6-5 Limits of Controlled Access for “On” Ramps 6-6 Limits of Controlled Access for “Off” ramps

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6.1 Introduction

The highway interchange design information presented in this chapter is a supplement to Chapter 10 of AASHTO’s “A Policy on Geometric Design of Highways and Streets.” Interchanges are areas of high speed conflicts and often have higher collision rates than the connecting links of the freeway system. Careful consideration should be given to the design elements to achieve a reasonable and prudent design.

6.2 Control of Access

Control of access restricts driveways and local roads from intersecting the highway. Control of access at interchanges is used to help improve the safety and capacity of the freeway entrances and exits. There should be control of access along the whole of all the ramps. To insure safety and free flow of traffic, ramps must be kept free of any intermediate roadway connections either by acquisition or outer frontage roads. Exhibits 6-01 through 6-04 illustrate the control of access required and freeway interchanges.

Control of access is a critical design element for freeways, ramps, and the ramp intersection area. Where control of access can not be achieved reasonably, a nonstandard feature justification is required per Chapter 2 of this manual.

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