THE 2001 GREEN BOOK

1
THE 2001 GREEN BOOK
Changes - Additions
Prepared by FHWA Office of Program
Administration
2
(No Transcript)
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Developed by the AASHTO Task Force on Geometric
Design
18 Departments of Transportation National
Association of County Engineers National League
of Cities American Public Works Association Port
Authority of NY, NJ Federal Highway Administration
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Format
Dual units Metric US Customary 8 ½ x 11
page size Bound Volume Exhibits References
Updated Speed Range 20 to 130 km/h
15 to 80 mph Ten Chapters
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UNITS

• Not exact (soft) conversion
• Not completely rationalized (hard) conversion
• Units developed independently
• Work in one system only
• Do not convert from one to other

6
Research National Cooperative Highway
Research Program
375 Median Intersection Design 383
Intersection Sight Distance 400 Stopping
Sight Distance 420 Access Management 439
Superelevation and Transitions HCM 2000
Highway Capacity Manual
7
Other Research/Publications
241 Truck Operating Characteristics 264
Roundabouts Transportation Research Circular
430 Interchange Operations FHWA-RD-97
-135 Older Driver Handbook FHWA-RD-00-067
Roundabouts An Informational Guide
8
Chapter 1Highway Functions

• No significant changes

9
Chapter 2 Design Controls and Criteria
Design Vehicles Older Drivers Design Speed
Definition Highway Capacity Access Control and
Access Management The Pedestrian Safety
10
Design Vehicles

• Four classes of design vehicles
• Passenger cars, include
• Cars, SUVs, Minivans, Vans, Pick-up trucks
• Buses (Separate category)
• Trucks
• Recreation vehicles

11
Design Vehicle

• Consider bicycles in selecting design vehicle
  when appropriate
• Added Considerations in selecting design
  vehicle provided

12
Buses Added

• Added
• Two school bus configurations
• Intercity bus
• City transit bus

13
Trucks

• Turning templates
• revised
• Autoturn
• Centerline turning radius added
• Revised symbols
• Typical dimensions
• Turning characteristics defined
• Truck tractors added

14
Older Drivers
. . . should be aware of the capabilities
and needs of older road users and consider
appropriate measures to aid their
performance. Expanded observations Expanded
countermeasures which may help alleviate
potential problems
Older Driver Highway Design Handbook
15
Speed

• Definitions revised
• Running speed discussion condensed
• two figures deleted
• Exhibit corresponding design speeds in
  both systems of measurement

16
Operating Speed

• OLD highest overall speed at which a
  driver can travel on a given highway under
  favorable weather conditions and under
  prevailing traffic conditions without at any
  time exceeding the safe speed as
  determined by the design speed on a section
  by section basis

NEW the speed at which drivers are
observed operating their vehicles during
free - flow conditions
17
Design Speed
OLD maximum safe speed that can be
maintained over a specific section of
highway when conditions are so favorable
that the design features of the highway
govern.
NEW a selected speed used to determine the
various geometric design features of the
roadway.
18
Speed

• Definitions revised
• Running speed discussion condensed
• two figures deleted
• Exhibit 2 - 29 corresponding design speeds
  in both systems of measurement

19
Speed

• Establishes
• Low - speed design 70 km/h 45 mph or
  less
• High - speed design 80 km/h 50 mph or
  more

20
Traffic Flow Relationships

• Updated consistent with 2000 HCM
• Exhibit 2 - 30 - Generalized speed volume -
  density curve replaces two figures

21
Highway Capacity

• Updated based on HCM 2000
• Rewritten to eliminate duplication of
  material
• Exhibit 2 31 Generalized definitions of
  Level of Service replaces Level of Service
  Characteristics
• Refers user to HCM for details

22
Access Control Access Management

• Rewritten and expanded to incorporate
  material from NCHRP 420
• Includes discussions on
• Basic principles
• Classifications
• Methods
• Benefits
• 3 Exhibits on crash rates added

23
The Pedestrian

• Sidewalk part of any street improvement
• Physical characteristics section replaced
  with Characteristics of Persons with
  Disabilities
• Mobility, Visual, and Developmental
• Added 600 mm 2 ft detectable warning
  strips at bottom of sidewalk ramps
• Listed 7 measures to reduce pedestrian -
  vehicle conflicts
• Eliminates HCM duplication
• Level of service generalized

24
Safety

• Deleted tables and figure with accident
  data
• Emphasizes access control in reducing
  crashes
• Include adequate shoulders in narrow medians
  for
• Emergency stops
• Use of emergency vehicles
• Added to list of factors to be considered
  in rural intersection design
• Crossroad sight distance
• Type of highway

25
Chapter 3 Elements of Design
Sight Distances Transition Designs Urban
Street Design Offtracking Horizontal
Alignment Turning Roadway Design Grades Vertical
Alignment
26
Stopping Sight Distance
Revised braking distance portion of equation
now based on deceleration ( a ) rather than
friction factor ( f )
2
V
Metric

d
0
.
V
t

278
254 f
Old
V
2
U.S.
V
d

1
47
.
t

30 f
Adopted a 3.4 m / sec2 11.2 ft /
sec2
27
A single value for each design speed
replaces the range of values used previously.
300
Stopping Sight Distance
250
200
Stopping Sight Distance, m
150
100
50
0
0
20
40
60
80
100
120
Initial Speed, km/h
28
Stopping Sight Distance on Grades

• Braking distance equation for grades
  modified to use deceleration rate (a)
• Reaction time must be added to braking
  distance from equation
• Exhibit 3 - 2 incorporates
• adjusted values

Metric
29
Other Sight Distances

• Decision Sight Distance
• Equations added to discussion
• Exhibit 3-3 modified reaction times
  added

• Passing Sight Distance
• Exhibit 3-7 expanded to
  130 km/h 80 mph

30
Criteria for Measuring
SSD
Eye Height -- 1080 mm 3.5 ft Object
Height -- 600 mm 2.0 ft
31
Superelevation

• Unchanged except for minor editing

• NCHRP 439 Superelevation
• Distribution Methods and
• Transition Designs -
• under consideration for
• next edition of Green Book

32
Transition Design Controls

• 3 transition methods discussed
• Tangent to curve
• Spiral to curve
• Compound curve
• Eliminated 2 - second rule
• Equation for minimum length of runoff
  provided
• Exhibit 3 27 Maximum Relative Gradients
  refined

33
Superelevation Runoff

• Exhibit 3 - 28 provides adjustments for
  runoff for number of lanes rotated
• Lengths vary proportionally to 3.6 m 12
  ft lane width
• Exhibit 3 - 29 based on 3.6 m 12 ft
  width
• Discussion on the Location of Runoff
  revised
• Exhibit 3 - 30 added providing allocations

34
Tangent Runout

• Added section on runout
• Equation provided to determine minimum length
• Lengths listed in Exhibit 3 - 29

35
Spiral Curve Transitions

• Corrected metric equation for minimum length
• Added two exhibits
• Exhibit 3 - 33 Maximum radius for use of
  spiral
• Exhibit 3 - 34 Desirable length of spiral
• Added equations for minimum and maximum
  length of spiral

36
Transitions - Miscellaneous

• Exhibit 3 31 and discussion added on
  limitations to the use of superelevation
  rates
• Axis of Rotation with Medians replaces Runoff
  with Medians
• Section added on minimum transition grades
• Section added on Turning Roadway Design

37
Urban Street Design

• Upper limit for low-speed urban design now
  70 km/h 45 mph rather than 60 km/h
  40 mph
• Exhibits 3 - 40 and 3 41 expanded to
  include 20 km/h 15 mph and 70 km/h
  45 mph

38
Offtracking

• Widths of turning roadways and widening of
  traveled way combined into section on
  Offtracking
• Exhibit 3 - 51 based on WB - 15 WB
  - 50
• Exhibit 3 - 52 added to provide adjustment
  factors for other design vehicles
• Tabular values based on
• dimensions in Chapter 2

39
Horizontal Alignment

• New height of eye and object incorporated
  into discussion.
• Exhibit 3 - 57 redone based on single
  stopping sight distance value.
• Passing sight distance discussion uses new
  height of eye and object

40
Horizontal Alignment
M
M
94 GB 90 GB
2001 GB
M middle ordinate, centerline inside lane
to sight obstruction
M shown is for horizontal curve with radius
of 200 m 656 ft
41
Grades

• Speed Distance Curves
• Developed for 120 Kg/kW 200 lb/hp
• Critical length of grade adjusted to
• reflect design vehicle

42
Grades

• Climbing lanes capacity discussion
• edited to eliminate duplicating HCM

• Passing Opportunities on 2 - lane Roads
• Passing lanes and 3 - lane sections combined

• Exhibit 3 - 68 Lengths of Turnouts revised

43
Vertical Alignment

• Length of vertical curve equations revised
  to incorporate new height of eye and
  height of object.
• Exhibits 3 - 75 and 3 76, K values
• Recalculated using new eye and object
  height
• Based on single value of stopping sight
  distance

44
2001 values are lower due to changes in
height of eye ( 1070 mm to 1080 mm ) and
height of object ( 150 mm to 600 mm ).
Since L K x A, length of vertical
curves will be shorter.
250
Crest Vertical Curves
200
150
Rate of Vertical Curvature, K
( length (m) per of A)
100
50
0
0
20
40
60
80
100
120
Initial Speed, km/h
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Vertical Alignment
94 GB 90 GB
2001 GB
Speed
SSD
K
SSD
K
80 km/h
112.8 - 139.4 m
32 - 49
130 m
26
50 mph
400 - 475 ft
110 - 160
425 ft
84
K rate of vertical curvature (
length ( m ) per of A ) or length (
ft ) per of A
K shown is for crest vertical curves
Since L K x A, length of vertical
curves will be shorter.
46
Vertical Alignment

• Equations for passing sight distance revised
  to incorporate new eye and object
  heights
• Exhibit 3 - 77 passing sight distance revised
  to reflect changes
• Exhibits 3 78 and 3 - 79 length of sag
  vertical curves recalculated using single
  value for stopping sight distance

47
Miscellaneous

• Emergency Escape Ramp bed depth
• increased to 1 m 3 ft

• Sight distance at undercrossings added

• Discussion on fencing added

• Combined traffic control devices under one
  heading

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Chapter 4 Cross Section Elements
Surface type Curbs Medians Pedestrians Bicycles
49
Curbs

• Section rewritten
• Visibility stressed
• Terminology
• Barrier replaced by vertical
• Mountable replaced by sloping

50
Miscellaneous

• Intermediate surface type deleted
• Discussion on medians updated
• Paragraph on grades of parking areas in
  Park - and - Ride Facilities revised

51
Pedestrians

• Separate topic on Sidewalks consolidated
  with Pedestrian Facilities
• Made compatible with proposed ADAAG
  standards and guidelines
• Sidewalk curb ramps
• Terminology changed
• Basic dimensions

52
Pedestrian References
AASHTO Guide for the Planning, Design,
and Operation of Pedestrian Facilities
(forthcoming )
FHWA - Designing Sidewalks and Trails (2
parts)
PROWAAC Building A True Community
Access Board Accessible Rights-of-Way A
Design Guide
53
Bicycles

• Added emphasis throughout

AASHTO Guide for the Development of
Bicycle Facilities 1999
54
Chapter 5Local Roads and Streets

• Exhibits updated to reflect changes in
  Chapter 3 and 9
• Superelevation
• Structures
• Clear zone
• Sight distance
• Parking lanes
• Intersections

55
Note

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

Guidelines for Geometric Design of Very Low
Volume Local Roads (lt 400 ADT )
(Forthcoming )
56
Exhibits

• Four Exhibits revised to be consistent with
  Chapter 3 revisions
• Exhibit 5 - 2 Stopping Sight Distance
• Exhibit 5 - 3 Passing Sight Distance
• Exhibit 5 - 13 Stopping Sight Distance
  Recreational Roads
• Exhibit 5 - 14 Passing Sight Distance
  Recreational Roads

57
Miscellaneous

• Maximum superelevation allowed for rural
  roads changed from 10 to 12
• Exhibit 5 - 6 Footnotes added for surfaced
  approaches and long bridges ( 30 m 100 ft
  )
• Clear zone width now 2 - 3 m
  7 10 ft
• Corner sight distance criteria deleted
  See Chapter 9
• Parking lanes added

58
Intersection Design

• Intersection design section reworded
• Exhibit 5 10 added
• Discusses two distinct radii to
  consider
• Effective turning radius
• Curb return radius

59
Chapter 6Collector Roads and Streets

• Exhibits
• Design speed for horizontal clearance
• Medians
• Parking lanes

60
Collector Exhibits

• Two exhibits updated to be consistent with
  Chapter 3 revisions
• Exhibit 6 - 2 Stopping Sight Distance
• Exhibit 6 - 3 Passing Sight Distance
• Table for maximum grades in previous
  editions replaced by two exhibits
• Exhibit 6 - 4 Maximum grades for rural
• Exhibit 6 - 8 Maximum grades for urban

61
Miscellaneous

• Design speed revised to upper limit of 70
  km/h 45 mph for low-speed design
• Minimum clear zone of 3 m 10 ft on
  rural collectors
• Median discussion and widths on urban
  collectors modified slightly

62
Parking Lanes

• Revisions
• Residential areas 2.1 to 2.4 m 7 to
  8 ft parking lane width

• Commercial areas 2.4 to 3.0 m 8 to
  11 ft parking lane width

• Industrial areas 2.4 to 3.0 m 8
  to 11 f t parking lane width

63
Chapter 7Rural and Urban Arterials

• Sight distance exhibit
• Widths
• Medians
• Curbs and shoulders
• Access management
• Turning radius for dual left turns

64
Exhibits

• Exhibit 7 - 1 Sight distance values
• moved from Provisions for Passing to
  Sight Distance in the chapter
• Exhibit 7 3
• adjusted lane width from 6.6 m
• 22 ft to 7.2 m 24 ft for 80
  km/h 50 mph and ADT of 1500
• to 2000
• column heading changed from
• DHV over 200 to ADT over 2000

65
Widths

• A minimum of 0.6 m 2 ft paved shoulder
  width should be provided for pavement
  support, wide vehicles, collision avoidance
  and bicycles
• Section on Bridges to Remain added to
  provide minimum widths for existing bridges that
  will be retained

66
Medians

• Advises against using 4 - lane undivided
  facilities
• Median discussion expanded and updated for
  both rural and urban
• Curb and Shoulders relocated to follow Lane
  Widths

67
Access Management

• Access Management replaces Access Control
• Refers to Chapter 2 discussion
• Discussion on left turns into and out of
  adjacent properties added

68
Miscellaneous

• Pedestrian Facilities updated
• Refers to Chapter 4
• Operation and Control Measures for Left -
  Turns
• Desirable turning radius 27 m 90
  ft

69
Chapter 8Freeways

• Updated to be consistent with other chapters
• Rural freeway discussion now precedes urban
• Allowance for height of resurfacing no
  longer specified
• Vertical clearance over railroads
• 6.6 m 21.5 ft minimum increased to 7.0
  m 23 ft

70
Chapter 9 Intersections
Types Functional area defined Discussion of
roundabouts Turning roadways Islands Intersection
sight distance Offset left turn lanes
71
Types

• 3 general types of intersections defined
• At-grade
• Grade separations without ramps
• Interchanges

72
Functional Area Defined

• Perception - reaction time
• Maneuver distance ( braking lane
• changing )
• Queue - storage distance ( accommodate
• longest queue expected )

Defined by physical area
Defined by functional area
73
Roundabouts

• Yield at entry
• Deflection of entering
• traffic
• Discussion only

FHWA-RD-00-067 Roundabouts An
Informational Guide
74
Turning Roadways

• Discussion reorganized
• All exhibits updated to be consistent with
  Chapter 2 design vehicles
• Maximum superelevation rate increased to 12
  where climate is favorable

75
Islands

• Minimum Design for Turning Roadways now part
  of General Characteristics

• Reversals in curvature for divisional
  islands reduced
• Minimum of 1165 m 3825 ft for rural
  areas
• Minimum 620 m 2035 ft for speeds up
  to 70 km/h 45 mph

• Free - flow Turning Roadways replaces
  Application at Terminals

76
Intersection Sight Distance
Six cases

• No control
• Stop control
• Yield control
• Signal control
• All-way stop control
• Left turn from major road

77
Gap Acceptance
Sight Triangles
Clear Sight Triangle
Clear Sight Triangle
A Approach Sight Triangles
Clear Sight Triangle
Clear Sight Triangle
B Departure Sight Triangles
78
Intersection Sight Distance
94 GB 90 GB
2001 GB
Speed
ISD
ISD
80 km/h
250 m
170 m
50 mph
840 ft
555 ft
ISD intersection sight distance for
turning left from stop onto major highway
79
Offset Left - Turn Lanes
Advantages

• Better visibility
• Reduced conflict
• More vehicles served

Parallel
Tapered
80
Miscellaneous

• Horizontal control see Chapter 3
• Deceleration length
• Discussion revised
• Additional design speeds and values included
• Discussion on driveways expanded

81
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
82
Miscellaneous

• Recommends separation of bicycle/pedestrian
  movement from vehicle movement through
  interchanges
• Single Point Urban Interchange discussed as
  separate type
• Exhibit 10-67 made consistent with Exhibit
  3-55

83
Access Control at Interchanges
Minimizes spillback on ramp crossroad Distance
for crossroad weaves Distance for merging
maneuvers Provides storage for turning vehicles
84
Miscellaneous

• Cautions against the use of minimum values
  for taper type entrances
• Exhibit 10-70 Acceleration lengths have been
  recomputed
• Adds a caution concerning volumes exceeding lane
  capacity on 2-lane ramps

85
Technical Corrections

• Exhibit 3 - 55 and Exhibit 10 - 67 - In
  metric side, under Case I column, replace
  with with no so it is identical with
  US Customary.
• Exhibit 3 - 76 - Delete and Sag from
  title.
• Exhibit 5 11 - Replace 5.5 under
  residential in the metric side with 2.2.

86
Technical Corrections

• Exhibit 10 - 60 is incorrect. It should be
  similar to Figure X-66 in 94 GB.
• Exhibit 10-71 - In the metric side, under
  the column All speeds in Acceleration
  lanes, change the second occurrence of 3
  to 4 Downgrade to 5 to 6
  Downgrade

87
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 )