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THE 2001 GREEN BOOK

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Chapter 5
Local Roads and Streets


Note

AASHTO is currently evaluating alternative criteria for local and collector roads with volumes < 400 vehicles per day

Guidelines for Geometric Design of Very Low - Volume Local Roads (< 400 ADT) (Forthcoming)


Exhibits

Four Exhibits revised to be consistent with Chapter 3 revisions:

Miscellaneous


Intersection Design

Intersection design section reworded

Chapter 6
Collector Roads and Streets


Collector Exhibits

Two exhibits updated to be consistent with Chapter 3 revisions: Table for maximum grades in previous editions replaced by two exhibits:

Miscellaneous


Parking Lanes


Chapter 7
Rural and Urban Arterials


Exhibits


Widths


Medians


Access Management

Access Management replaces Access Control

Miscellaneous


Chapter 8
Freeways


Chapter 9
Intersections

Types
Functional area defined
Discussion of roundabouts
Turning roadways
Islands
Intersection sight distance
Offset left turn lanes

Types

3 general types of intersections defined:

Functional Area Defined

Schematic drawing of an intersection with physical area highlighted.
Defined by physical area
Schematic drawing of an intersection with functional area highlighted
Defined by functional area

Roundabouts

  • Yield at entry
  • Deflection of entering traffic
  • Discussion only
FHWA-RD-00-067 Roundabouts: An Informational Guide
Aerial view of modern roundabout intersection.

Turning Roadways


Islands


Intersection Sight Distance

Six cases

Gap Acceptance
Sight Triangles

Schematic of an intersection with approach and departure sight triangles highlighted

Intersection Sight Distance

Speed 94 GB [90 GB] 2001 GB
ISD ISD
80 km/h
[50 mph]
250 m
[840 ft]
170 m
[555 ft]

ISD = intersection sight distance for turning left from stop onto major highway


Offset Left - Turn Lanes

Advantages:
  • Better visibility
  • Reduced conflict
  • More vehicles served
TOP: Schematic of an intersection with offset left-turn lanes utilizing a parallel design. BOTTOM: Schematic of an intersection with offset left-turn lanes utilizing a tapered design.

Miscellaneous


Chapter 10
Grade Separations and Interchanges

Access separations and control on crossroad at interchanges
Turning roadway widths
Single - point urban interchanges
Superelevation and cross slopes
Two lane entrance ramps


Miscellaneous


Access Control at Interchanges

Minimizes spillback on ramp & crossroad
Distance for crossroad weaves
Distance for merging maneuvers
Provides storage for turning vehicles

Miscellaneous


Technical Corrections


Technical Corrections


Future Research

Truck impacts on criteria (underway)
Improved design for freeway speed change lanes (proposed)
Design criteria and warrants for right turn deceleration (proposed)
Auxiliary through lanes and lane drops (proposed)
Passing sight distance (proposed)

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