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AASHTO. Technical Committee on Geometric Design. AASHTO Standing Committee on Highways. AASHTO Subcommittee on Design.

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AASHTO

Technical Committee on Geometric Design


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AASHTO Standing Committee on Highways

AASHTO Subcommittee on Design

Provide a focal point and working group for developing and recommending AASHTO geometric design criteria. This assignment includes formulating new and revised criteria to keep current all geometric design standards, polices, and guidelines.

AASHTO Technical Committee on Geometric Design


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AASHTO Technical Committee on Geometric Design

  • States from each of the four regions

  • FHWA; serves as secretary

  • American Public Works Association

  • League of Cities

  • National Association of County Engineers


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Publication Responsibilities

  • A Policy on Accommodation of Utilities within Freeway Right of Way, 2005

  • A Policy on Design Standards – Interstate System, 2005

  • Guide for Accommodating Utilities within Highway Right of Way, 2005

  • Guide for Development of Rest Areas on Major Arterials and Freeways, 2001


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Publication Responsibilities

  • Guide for the Planning, Design, and Operation of Pedestrian Facilities, 2004

  • Guidelines for Geometric Design of Very Low Volume Local Roads (ADT < 400), 2001

  • Guide for the Development of Bicycle Facilities, 1999 (NCHRP 20-7 Project Coordinated with Technical Committee on Non-motorized Transportation)


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Research Proposals and Oversight

  • Designing Roadway Transitions from Rural Highways to Urban/Suburban Highways or Streets

  • Design Speed Alternatives for Selecting Geometric Criteria

  • One – and Multi-Lane Loop Ramp Design


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Research Proposals and Oversight

  • Updated Headlamp Design Criteria for SAG Vertical Curves

  • Superelevation Criteria for Sharp Horizontal Curves on Steep Grades

  • Accommodating Oversize/Overweight Vehicles at Roundabouts


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A Policy on Geometric Design of Highways and Streets

( Green Book )


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Chapter 1

Highway Functions


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Chapter 1Highway Functions


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Chapter 1Highway Functions


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Chapter 1Highway Functions


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Chapter 1Highway Functions


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ProposedChanges

  • Designer Consideration of the Context of the Project Area

  • Highlights the Flexibility Available to Encourage Choosing Design Criteria:

  • Consistent with the Context of the Project

  • Needs and Value of the Community

  • With Respect to Economic Limitations

Chapter 1


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Chapter 2

Design Controls and Criteria


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Chapter 2

Design Control & Criteria


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Chapter 2

Design Control & Criteria


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Proposed Changes

  • Adding SU-40 Single Unit Truck (3-axle)

  • Removing WB-50 Semitrailer Truck and Replacing with WB-62

  • Adding WB-92B – Rocky Mountain Double

Chapter 2


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Chapter 3

Elements of Design


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Chapter 3

Elements of Design


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Chapter 3

Elements of Design


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Proposed Changes

  • Stopping Sight Distance Tables Clarified Whether on Level, Wet Weather, or Grades

  • Passing Sight Distance for Two-Lane Highways Revised (NCHRP Report 605)

  • Height of Object will Include Discussion About Decision Sight Distance

Chapter 3


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Proposed Changes continued

  • Revision Method for “Lane Drop Taper Length” for Passing Lane Sections

  • Lighting – Updated to Conform to the Roadway Lighting Guide

Chapter 3


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Chapter 4

Cross Section Elements


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Proposed Changes

  • Traveled Way Definition Revised to be Consistent with Roadside Design Guide

  • Rumble Strip Section Added Based on State Experience and TRB/FHWA Research

Chapter 4


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Proposed Changes continued

  • Roadside Design Discussion Provided in a More Consistent Format with the Roadside Design Guide

  • Sidewalks and Curb Ramps – Updating Discussion to Conform to AASHTO Pedestrian Guide and ADAAG

Chapter 4


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Chapter 5

Local Roads and Streets


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Chapter 5

Local Roads and Streets


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Chapter 5

Local Roads and Streets


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Proposed Changes

  • Updated Reference to AASHTO LRFD Bridge Design Specifications

Reorganized Clear Zone Discussion

to Roadside Design

Added Discussion of Level of Service in Rural/Urban

Chapter Reorganized to Generally Follow Other Functional Chapters

Chapter 5


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Chapter 6

Collector Roads and Streets


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Chapter 6

Collector Roads and Streets


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Chapter 6

Collector Roads and Streets


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Proposed Changes

  • Chapter Reformatted to Provide Some Consistency with other Functional Classification Chapters

  • Adding Text About Selection of LOS for this Functional Classification

  • Roadside Design Discussion

Chapter 6


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Chapter 7

Arterials

(Rural & Urban)


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Chapter 7

Arterials (Rural & Urban)


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Proposed Changes

  • Added Discussion About Characteristics of Urban Arterials

  • Added Discussion About LOS Selection for Urban Arterials

  • Revised Discussion About the Relationship Between Design Speed and Lane Width

Chapter 7


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Proposed ChangesContinued

  • Benefits of Medians to Pedestrians in Urban Areas

  • Added Discussion About Off-Setting Left Turn Lanes When Selecting Median Widths

Chapter 7


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Chapter 8

Freeways


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Chapter 8

Freeways


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Proposed Changes

  • Added Discussion on Superelevation Rates on Freeways Considering Snow/Ice, Viaducts, and Section Consistency

  • Reformat to Generally Sequence Other Functional Classification Chapters

  • Reorganize Clear Zone Discussion to Roadside Design

Chapter 8


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Chapter 9

Intersections


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Chapter 9

Intersections


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Proposed Changes

  • Chapter Being Reformatted to Provide Better Sequence of Design Material

  • Adding Discussion of Intersection Capacity Based on HCM

  • Updating Discussion of Roundabouts and Adding Discussion of Continuous Flow Intersections

Chapter 9


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Proposed Changes continued

  • Expanding the Discussion of Indirect Left Turns and U-turns

  • Based on TRB Access Management Manual:

  • Definition of Functional Area

  • Components of Auxiliary Lanes

  • Deceleration Length Discussion

  • Adding Design Criteria for Double/Triple Let Turns – NCHRP 505

Chapter 9


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Chapter 10

Grade Separations and Interchanges


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Chapter 10

Grade Separations & Interchanges


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Proposed Changes

  • Updating Exhibits for Directional/Semi-directional Interchanges

  • Including an Exhibit for Diamond Interchange with Roundabout Intersection Control

  • Providing Discussion of Two-lane Loop Ramp Design

  • Providing Additional Guidance on Ramp Metering

Chapter 10


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Green Book Schedule

  • Currently doing a technical mark up for consistency

  • Committee meeting in the Fall of 2009

  • One more technical review

  • Ballot in the First Quarter of Calendar 2010


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Technical Committee on Geometric Design

AASHTO


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