# Presentation: 353484

## THE  2001  GREEN  BOOK

- <date/time>

**THE  2001  GREEN  BOOK**

**Changes  -  Additions**

**  ****Prepared by:**
**   ****FHWA – Office of Program Administration**

**Notes:**
Title Slide

The newest edition, the 4th, of AASHTO’s “A Policy on Geometric Design of Highways and Streets” became available in June 2001.  This presentation summarizes the changes and additions to the 1994 (metric version) and the 1990 (US Customary) editions.  It combines the two systems of measurement into one volume.

NEXT

## Slide 2

**Notes:**
The policy has existed since 1950 in various forms.
Note various editions.

The initial compilation in 1950 was updated in 1952 and followed by (NEXT) 2 editions of the Blue Book for rural design, (NEXT) 2 editions of the Red Book for urban design, and (NEXT) three editions of the Green Book combining rural and urban design.

NEXT

## Developed by the AASHTO Task Force

- <date/time>

**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**

**Notes:**
The policy was developed by the AASHTO Task Force on Geometric Design comprised of 18 members from State Departments of Transportation from all regions of the country.  In addition to the DOT representatives, 3 national associations, Port Authority of New York and New Jersey, and the Federal Highway Administration were represented.  Each member of the Task Force had responsibility for a part of the finished product.

NEXT

## Format

**8 1⁄2  x  11  page  size**
**Bound  Volume**
**Exhibits**
**References  Updated**
**Speed  Range  20  to  130  km/h**
**                     ****[15  to  80 mph]**
**Ten  Chapters**

**Format**

**Notes:**
Green Book is a single volume with dual units.  Metric first with US Customary in square brackets following.

Larger pages in a bound volume.

Exhibits replace tables and figures.  Numbered sequentially by chapter.

References have been updated to incorporate information developed since the last edition.

Speed range increased.

Still 10 chapters.

NEXT

## UNITS

- <date/time>

**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**

**Notes:**
A word of caution on the use of the units.  The Forward states that the units for the numerous elements were developed independently and their relationship is neither an exact (soft) conversion nor a completely rationalized (hard) conversion.  The user is advised to work entirely in one system and not attempt to convert directly between the two.

NEXT

## 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**

**Notes:**
NCHRP Reports form a basis for revisions incorporated.  
(Mention the ones of interest)
Two of the most significant changes are in the sight distance criteria from NCHRP 383 and 400.

NEXT

## 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**

**Notes:**
Other research and publications used to update the material included: (mention ones of interest)

NEXT

## Chapter  1Highway  Functions

- <date/time>

**Chapter  1****Highway  Functions**

**No  significant  changes**

**Notes:**
There were no significant changes made to Chapter 1 – Highway Functions.

NEXT

## Chapter  2

** ****Design  Controls  and  Criteria**

**Design  Vehicles**
**Older  Drivers**
**Design  Speed  Definition**
**Highway  Capacity**
**Access  Control  and  Access  Management**
**The  Pedestrian**
**Safety**

**Notes:**
Chapter 2 – Design Controls and Criteria contains changes or additions in 7 sections.

Read the list.

Each section is discussed in the following slides.

NEXT

## Design  Vehicles

**Four  classes  of  design  vehicles:**
**Passenger  cars,  include:**
**Cars,  SUV’s,  Minivans,  Vans,  Pick-up trucks**
**Buses  (Separate category)**
**Trucks**
**Recreation  vehicles**

**Notes:**
There are now four classes of vehicles.  The classes of design vehicles has been revised to categorize buses separately creating the four classes instead of the three included in previous editions.

Of note are the types of vehicles included as passenger cars (List).

NEXT

## Design Vehicle

**Consider  bicycles  in  selecting  design vehicle  when  appropriate**
**Added  –  Considerations  in  selecting design  vehicle  provided**

**Notes:**
We need to remember to consider bicycles as a design vehicle under appropriate conditions.

Additional considerations for selecting a design vehicle have been identified for a series of conditions that may occur on the roadway.

NEXT

## Buses Added

**Added:**
** ****Two  school  bus  configurations**
** ****Intercity  bus**
**City  transit  bus**

**Notes:**
Four design vehicles, all bus configurations, have been added to the 15 design vehicles available previously.  They include two school buses, an intercity bus, and a city transit bus.

NEXT

## Trucks

**Trucks**

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

**Notes:**
The design vehicle turning templates have been revised using Autoturn.  Autoturn is a proprietary software program which can simulate truck turning movements.  Several of the symbol designations have been modified (e. g. WB-18 is now WB-20D).  The typical dimensions were reviewed and adjusted to reflect the truck fleet, which lead to the revised turning template.  A centerline turning radius has been added to the template.

Two additional Exhibits have been added illustrating turning characteristics (2-11)and typical truck tractors (2-12).

NEXT

## 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**

**Notes:**
The group of drivers aged 65 and older is increasing significantly.  As a group, they have the potential to adversely affect the highway system’s safety and efficiency.  The designer -  read quote.

The discussion pertaining to the older driver has been expanded in the section on Driver Performance.  The list of countermeasures which may help alleviate potential problems has been expanded.

The Older Driver Highway Design Handbook is referenced for additional information.

NEXT

## Speed

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

**Notes:**
Revised definitions related to speed have been incorporated.  These revisions are based on research and action by the AASHTO Executive Board.

NEXT

## 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**

**Notes:**
Read the old definition for operating speed.  (NEXT) Read new definition.

NEXT 

## 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.**

**Notes:**
Read the old definition. (NEXT) read new definition.  The discussion of design speed has been revised accordingly.

The selected design speed should be consistent with the speed drivers are likely to expect on a given highway facility.

NEXT

## Speed

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

**Notes:**
Other revisions in the speed section include a condensation of the discussion of running speed together with deleting two figures, related to the discussion in previous editions.

Exhibit 2-29 has been added showing corresponding design speeds in both systems of measurement.  This table should be used in converting the units of measurement of design speeds.

NEXT

## Speed

**Establishes:**
**Low - speed  design:  70  km/h  [45  mph]  or  less**
**High - speed  design:  80  km/h  [50 mph]  or  more**

**Notes:**
The new edition eliminates the discussion of intermediate design speed.  As a result, the upper limit for low-speed design is established at 70 km/h [45 mph].  High-speed design is 80 km/h [50 mph] or more.

NEXT

## Traffic  Flow  Relationships

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

**Notes:**
The discussion of Traffic Flow Relationships has been updated to be consistent with the 2000 HCM.  

A generalized speed-volume-density curve replaces the two similar curves in the previous edition.

NEXT

## 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**

**Notes:**
The entire discussion on capacity has been rewritten to agree with the 2000 HCM.  Information from the HCM that was duplicated in the Green Book has been eliminated.  The table defining Levels of Service has been made more general in nature.  For the details on capacity, the user is referred to the manual.

NEXT 

## 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**

**Notes:**
This section has been rewritten and expanded to incorporate material from NCHRP Report 420.  It includes discussion of the basic principles, access classifications , methods of controlling access, and the benefits of access control.  Three exhibits from the NCHRP report have been added illustrating crash rates by type of median for urban and suburban areas and rural areas, and crash rates by unsignalized and signalized access density in urban and suburban areas.

NEXT

## 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**

**Notes:**
The section on the pedestrian has been revised to add a statement that sidewalk should be a part of any urban/suburban street improvement.

The discussion of physical characteristics has been replaced by a discussion of characteristics of persons with disabilities, including mobility, visual and development impairments.

Added the 600 mm [2 ft] detectable warning strip at the bottom of the sidewalk ramp as an aid to the visually impaired.

Seven measures to reduce pedestrian-vehicle conflicts have been listed.

Duplicate material from the HCM has been deleted as appropriate and the Level of Service discussion made more general.

NEXT

## 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**

**Notes:**
The tables and figure containing accident data in the previous edition have been deleted, but the discussion has been retained.

The discussion on safety emphasizes the value of access control in reducing crashes.

In the discussion relating to narrow medians the statement “However, if a narrow median is proposed on a high-speed highway, the design should include adequate shoulder widths in the median for emergency stops and emergency vehicle use.

The paragraph on improving safety at intersections has been revised to include sight distance and type of highway as factors.

NEXT

## Chapter  3

**Elements  of  Design**

**Sight  Distances**
**Transition  Designs**
**Urban  Street  Design**
**Offtracking**
**Horizontal  Alignment**
**Turning  Roadway  Design**
**Grades**
**Vertical  Alignment**

**Notes:**
Eight sections of Chapter 3 – Elements of Design have been revised.

Sight distances, specifically stopping sight distance, and its effect on vertical alignment are the two sections containing the most significant changes.

NEXT

## Stopping  Sight  Distance

**Revised  braking  distance  portion of**
**equation – now  based  on deceleration ( a )**
**rather  than  friction  factor  ( f )**

**    ****Adopted  **a** **** –****  ****3.4  m / sec****2**
**	****[ 11.2  ft / sec****2 ****]**

**Metric**

**U.S.**

**254 f**

**d**

**V**

**t**

**=**

**+**

**0**

**278**

**.**

**2**

**V**

**V**

**d**

** ****=**

**1**

**47**

**.**

**t**

**+**

**V**

**2**

**Old**

**30 f**

**Notes:**
Revised the braking distance portion of the equation – now based on deceleration (a) rather than friction factor (f).
The equations shown for stopping sight distance are from the 1994 Green Book (metric) and the 1990 Green Book (U.S.).
The first half of the equation represents the distance traveled during perception-reaction time.
The second half of the equation represents the distance traveled while applying the brakes and coming to a stop.
For the 2001 Green Book, the braking distance portion is based on driver deceleration rate rather than friction factor.
Substituting and rearranging the terms, the new equation becomes

NEXT

Note that the constant also changes, in addition to substituting a for f

NEXT

The deceleration rate adopted is 3.4 m/sec2 [11.2 ft/sec2]

## A  single  value  for  each  design  speed  replaces  the range  of  values  used  previously.

**0**

**50**

**100**

**150**

**200**

**250**

**300**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**Initial  Speed,  km/h**

**Stopping  Sight  Distance,  m**

**Stopping  Sight  Distance**

**Notes:**
The graph illustrates the previous range of values for stopping sight distance. The upper limit of the range is shown with a pink circle, and the lower limit is shown with a dark blue diamond.  (NEXT) Because of the change in the criteria used, a single value applies for stopping sight distance.  (The graph of the single value will come in automatically.)  Shown here in black.

## 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**

**Notes:**
The equation for braking distance on grades has also been modified to incorporate the deceleration rate.  To the braking distance, the reaction time must be added to determine the total sight distance required.  Exhibit 3-2 incorporates the adjusted values.

NEXT

## 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 ]**

**Notes:**
The discussion on Decision Sight Distance has been revised to include the equations used to calculate the values.  The times used in the calculations have been incorporated into Exhibit 3-3 which provides the lengths for Decision Sight Distance for 5 avoidance maneuvers. (NEXT)

The Passing Sight Distance Exhibit has been expanded to 130 km/h [80 mph]. 

NEXT

## Criteria  for  Measuring

**SSD**

** ****Eye  Height  --  1080  mm  [ 3.5  ft ]**
** ****Object  Height  --  600  mm  [ 2.0  ft]**

**Notes:**
A major change in the criteria for measuring sight distance has been adopted from NCHRP Report 400.  Based on the report the height of object for SSD has been increased to 600 mm [2.0 ft].  The height of object approximates the height of a vehicle tail light.  A minor increase of 10 mm was also adopted in the height of eye to 1080 mm [3.5 ft] and is based on a study which indicated the average eye height to be 1080 mm.  (NEXT)

The height of eye and object for passing sight distance have also changed.  The height of eye was increased slightly to 1080 mm [3.5 ft] and the height of object was decreased to 1080 mm [3.5 ft].  The object height is based on a vehicle height of 1330 mm [4.35 ft], which represents the 15th percentile height in the current passenger car population, less an allowance of 250 mm [0.82 ft].  This represents a near-maximum value for the portion of the vehicle height needed to be visible for another driver to recognize a vehicle as such.

The study recommended the eye height for drivers of large trucks as 2330 mm [7.6 ft].

NEXT

## Superelevation

**	****Distribution  Methods  and**
**	****Transition  Designs  -  **
**	****under  consideration  for**
**	****next  edition  of  Green  Book**

**Superelevation**

** ****Unchanged  except  for  minor  editing**

**Notes:**
The discussion on superelevation is unchanged except for some minor editing.  NCHRP Report 439 on superelevation and transitions is being reviewed by the Task Force on Geometric Design for inclusion in a future edition of the Green Book.

NEXT

## 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**

**Notes:**
Three methods of transitioning from a normal crown section to a fully superelevated section are discussed separately.  They are tangent to curve, spiral to curve, and compound curve.

To determine the minimum length of runoff required for transitioning, an equation is provided and the 2-second rule has been eliminated.  These changes are based on the results and recommendations of NCHRP Report 439 on superelevation distribution and transitions.

As a result, Exhibit 3-27 which provides a table of relative gradients to be used to determine the length of runoff has been refined.

NEXT

## 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**

**Notes:**
An addition to the discussion of superelevation runoff is an exhibit developed to provide adjustment factors to the length of runoff for the number of lanes rotated.  The adjustment is based on a lane width of 3.6 m [12 ft].  For other lane widths, the factor varies proportionally to the 3.6 m [12 ft] width.  Exhibit 3-29 provides minimum runoff lengths for the various design speeds and superelevation rates.

The location of runoff with respect to the end of curve discussion has been revised and Exhibit 3-30 provided.  This exhibit shows the portion of runoff located prior to the curve based on  design speed and number of lanes rotated.

NEXT 

## Tangent  Runout

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

**Notes:**
A section has been added to discuss tangent runout and an equation provided to determine minimum length.  The lengths determined using the equation are listed in Exhibit 3-29.

NEXT

## 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**

**Notes:**
The equation, in the metric system, to determine the length of spiral has been corrected.  The constant in the equation in previous editions was incorrect.

Exhibits and equations have been included in the discussion on spirals.  Exhibit 3-33 shows the maximum radius for use of a spiral transition.  Exhibit 3-34 illustrates the desirable length of spiral curve transitions.  Equations are provided in the text to determine both minimum and maximum lengths of spirals.

NEXT

## 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**

**Notes:**
There are several additional modifications, revisions and changes in the section discussing transitions.  An Exhibit and discussion have been added on limitations to the use of superelevation rates.

Axis of Rotation with Medians replaces the discussion of Runoff with Medians.

A section is added to discuss minimum grades to use in transition areas.  Situations occur where the pavement cross slope or the longitudinal grade may not be sufficient to adequately drain the pavement laterally.  The discussion provided two techniques to alleviate these two potential problems.

A section has been added to discuss Turning Roadway Design.

NEXT

## 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]**

**Notes:**
The upper limit for low-speed urban design is 70 km/h [45 mph] rather than the 60 km/h [40 mph] in previous editions.  Exhibit 3-40 and Exhibit 3-41 have been expanded to include a range between 20 km/h [15 mph] and 70 km/h [45 mph].  

NEXT

## 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**

**Notes:**
Widths of Turning Roadways and Widening of Traveled Way have been combined and reorganized into a new section entitled Offtracking.

Exhibit 3-51 on traveled way widening on open highway curves on two-lane highways is based on a WB-15 [WB-50] design vehicle.  A new exhibit (3-52) is provided to give adjustment factors for other design vehicles.  All calculations to determine the values presented in these exhibits are based on the dimensions in Chapter 2.

NEXT

## 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**

**Notes:**
Horizontal alignment has been rewritten to incorporate the revised eye height and object height for both stopping and passing sight distances.  Exhibit 3-57 reflects the single stopping sight distance value.

NEXT

## Horizontal  Alignment

**M  =  middle  ordinate,  centerline  inside  lane  to  sight  obstruction**

**M  shown  is  for  horizontal  curve with  radius  of  200  m  [ 656  ft ]**

**94****  ****GB  [90   GB]**

**M**

**2001  GB**

**M**

**Notes:**
The differences between the previous editions and the 2001 GB are illustrated in this table for 80 km/h [50 mph] for a curve of 200 m [656 ft].  The new values fall within the range previously used.

NEXT 

## Grades

**Speed  –  Distance  Curves:**
**Developed  for  120  Kg/kW  [ 200  lb/hp ]**
**Critical  length  of  grade  adjusted  to**
**  ****reflect  design  vehicle**

**Grades**

**Notes:**
Speed-distance curves for trucks on grades have been recalculated to reflect the current truck fleet.  The curves are now for 120Kg/kW [200 lb/hp].  The critical length of grade (Exhibit 3-63) reflects this change.

NEXT 

## 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**

**Notes:**
In the discussion on grades, material on capacity which duplicated the HCM has been removed.  The user is directed to the HCM for the appropriate information.  (NEXT)

The discussion on passing opportunities has combined Passing Lanes and Three-lane Sections.  (NEXT)

The lengths of turnouts presented in Exhibit 3-68 have been revised.

NEXT

## 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**

**Notes:**
The equations for the length of vertical curve have been revised to incorporate the revised height of eye and object used in determining stopping sight distance.  The design controls (K) provided in Exhibits 3-75 and 3-76 have been adjusted accordingly.

NEXT

## 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.

**0**

**50**

**100**

**150**

**200**

**250**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**Initial  Speed,  km/h**

**Rate  of  Vertical  Curvature, K****  **

**( length  (m)  per  %  of  A)**** **

**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.**

**Crest  Vertical  Curves**

**Notes:**
The graph shows the range of values determined in previous editions with the upper limit in pink circles and the lower limit in dark blue diamonds.  (NEXT)

The black line illustrates the the new values.  (NEXT)

The 2001 values are lower due to the changes in the height of eye and object. Since the K values are generally smaller than previously the vertical curve determined will be shorter.

NEXT

## Vertical  Alignment

**80 km/h**

**112.8 - 139.4 m**

**32 - 49**

**130 m**

**26**

**[50 mph]**

**[400 - 475 ft]**

**[110 - 160]**

**[425  ft]**

**[84]**

**Speed**

**94 GB [90  GB]**

**2001 GB**

**SSD**

**K**

**SSD**

**K**

**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.**

**Notes:**
The table shown here illustrates the differences in K values for crest vertical curves between previous editions and the 2001 Green Book.

Since the K value is smaller the length of vertical curve required that provides stopping sight distance will be shorter.

NEXT

## 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**

**Notes:**
The equations for passing sight distance values of K have been revised to incorporate the new heights of eye and object and the values shown in Exhibit 3-77 revised to reflect the changes.

The two exhibits (3-78 and 3-79) for the K value for sag vertical curves have been recalculated using the single stopping sight distance value.

NEXT

## 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**

**Notes:**
The depth of the arrester bed on emergency escape ramps has been increased to 1 m [3 ft] based on research. (NEXT)

A discussion, illustration and equations to consider sight distance at undercrossings have been added.  (NEXT)

The separate section on Signing and Marking and Traffic Signals have been combined under one heading titled Traffic Control Devices.

NEXT

## Chapter  4

**Curbs**
**Medians**
**Pedestrians**
**Bicycles**

**Chapter  4**
**Cross  Section  Elements**

**Notes:**
Five areas in Chapter 4 - Cross Section Elements have been modified.

LIST

NEXT

## Curbs

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

**Notes:**
The section on Curbs has been rewritten.  In the discussion visibility is stressed.  The terminology applied to curbs has also been revised.  Barrier curb is replaced by vertical curb.  Mountable curb has been replaced by sloping curb.

(NEXT)

## Miscellaneous

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

**Notes:**
There are several other areas in the chapter that have been revised.  In pavement, intermediate surface type has been deleted.

The discussion on Medians has been updated based on research results.

The paragraph on grades of parking areas in Park-and Ride Facilities has been revised to incorporate additional information.

NEXT

## Pedestrians

** ****Made  compatible  with  proposed ****	****ADAAG  standards  and  guidelines**
** ****Sidewalk  curb  ramps**
** ****Terminology  changed**
** ****Basic  dimensions **

**Pedestrians**

**Notes:**
The separate topic on Sidewalks has been consolidated with Pedestrian Facilities to have all the information related to pedestrians in one location.

The section incorporates proposed ADAAG standards and criteria.

Some terminology has changes in this section also.  Curb-cut ramps are now sidewalk curb ramps.  Some basic dimensions are included in the text.

NEXT 

## 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**

**Notes:**
The are a number of references that can be used when considering the development of pedestrian facilities.

List those of interest.

NEXT

## Bicycles

-   **Added   emphasis   throughout**

**AASHTO  –  Guide  for  the**
**Development  of  Bicycle**
**Facilities  1999**

**Notes:**
Emphasis has been added throughout the chapter relating to the consideration of bicycles.  The primary source of information is the AASHTO Guide for the Development of Bicycle Facilities.

NEXT

## Chapter 5Local  Roads  and  Streets

**Chapter 5****Local  Roads  and  Streets**

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

**Notes:**
There have been seven areas modified in Chapter 5 – Local Roads and Streets.

NEXT

## 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 )**

**Notes:**
It is noted in the chapter, as well as Chapter 4 and 6, that AASHTO is currently evaluating alternative criteria for very low volume local and collector roads.  Very low volume is considered to be those roads with an ADT less than 400 vehicles per day.

NEXT

## 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**

**Notes:**
Four exhibits have been revised to be consistent with the changes in procedures and criteria in Chapter 3.  The four exhibits pertain to stopping and passing sight distance.

NEXT

## 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**

**Notes:**
NEXT

The maximum superelevation for rural roads has been increased from 10% to 12% for favorable climatic conditions. (NEXT)

Footnotes have been added to Exhibit 5-6 concerning surfaced approaches and long bridges (30 m [100 ft]).

The minimum clear zone width has been changed from 3 m [10 ft] to a range of 2-3 m [7-10 ft].  (NEXT)

The corner sight distance criteria and its discussion has been deleted and a reference made to the Chapter 9 discussion on Intersection Sight distance.  (NEXT)

A discussion on parking lanes on local roads has been added.

NEXT

## Intersection Design

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

**Notes:**
The discussion of intersection design has been reworded and an Exhibit 5-10 added.  The text discusses two distinct radii to consider – effective turning radii and the curb return radius.  Exhibit 5-10 illustrates these two radii.

NEXT

## Chapter  6Collector  Roads  and  Streets

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

**Notes:**
Four areas in Chapter 6 – Collector Roads and Streets contain revisions.

LIST

NEXT

## 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 **

**Notes:**
The two exhibits pertaining to sight distance have been revised to be consistent with the changes in Chapter 3.  Exhibit 6-2 contains design controls for Stopping Sight Distance for both crest and sag vertical curves.  Exhibit 6-3 contains the design controls for Passing Sight Distance for crests.

The exhibit in previous editions which contained maximum grades for both rural and urban conditions has been split into separate tables.  Exhibit 6-4 provides maximum grades for rural areas, while Exhibit 6-8 provides the maximum grade for urban areas.

NEXT

## 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**

**Notes:**
The upper limit of design speed has been increased to be consistent with the discussion in Chapter 2.  The upper limit is now 70 km/h [45 mph].  With the increase in speed the minimum clear zone criteria now applies at 70 km/h [45 mph].

The discussion and widths pertaining to medians on urban collectors has been modified slightly.

NEXT 

## 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**

**Notes:**
A discussion on parking lanes has been added in the part of the chapter pertaining to Urban Collectors.  Parallel parking is generally acceptable when the noted widths are available in residential (NEXT), commercial (NEXT) and industrial (NEXT) areas.  In commercial and industrial areas, parking is usually provided on both sides of the street.

NEXT  

## Chapter  7Rural  and  Urban  Arterials

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

**Notes:**
Six areas in Chapter 7 – Rural and Urban Arterials have been modified.

NEXT

## 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**

**Notes:**
Sight distance values were added as Exhibit 7-1.  This information was moved from a section on Provisions for Passing and replaces the similar table in that section.

Two cells in Exhibit 7-3 have been revised.  For a speed 80 km/h [50 mph] and an ADT over 2000 the lane width has been adjusted from 6.6 m [22 ft] to 7.2 m [24 ft].  The last column heading has been revised from a DHV over 200 to ADT over 2000.

NEXT

## 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**

**Notes:**
A minimum paved shoulder width of 0.6 m [2 ft] should be provided for pavement support, wide vehicle overhang, collision avoidance and bicycles.

A new section on Bridges to Remain on urban arterials has been added to provide minimum width information where a structure is to be retained.

NEXT

## 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**

**Notes:**
The last two sentences included in the discussion of Multilane Undivided Arterials advises against four-lane undivided facilities.

The section on medians in both rural and urban areas has been reworded and expanded.

In the Urban section, Curb and Shoulders discussion follows the discussion of lane widths.

NEXT

## Access  Management

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

**Notes:**
Access Management replaces Access Control in the Chapter and refers to the material added in Chapter 2.  A discussion on left turns into and out of adjacent properties has been added to the section.

NEXT

## Miscellaneous

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

**Notes:**
The discussion on Pedestrian Facilities has been updated and refers to Chapter 4.

In the section discussing Operation and Control Measures for Left-turns, a desirable turning radius of 27 m [90 ft] is indicated.

NEXT

## Chapter 8Freeways

**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]**

**Notes:**
Chapter 8 – Freeways has been updated and reorganized to be consistent with the material in other chapters.  The rural discussion now precedes the urban discussion to be similar to the other chapters on functionally classified facilities.

An allowance for resurfacing in the Vertical Clearance discussion remains, but a specified value is no longer provided.  The vertical clearance over railroads has been increased to 7 m [23 ft] from a previous minimum of 6.6 m [21.5 ft].

NEXT

## Chapter  9

**Intersections**

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

**Notes:**
Seven areas in Chapter 9 - Intersections have been modified in this edition.

NEXT

## Types

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

**Notes:**
An intersection is defined as the general area where two or more highways cross.  Three general types of intersections are defined: at-grade, grade separations without ramps, and interchanges.  The latter two types are discussed in detail in Chapter 10 – Grade Separations and Interchanges.

NEXT  

## Functional  Area  Defined

** ****Maneuver  distance  ( braking  &  lane**
**  ****changing )**
** ****Queue  -  storage  distance  ( accommodate**
**    ****longest  queue  expected )**

**Functional  Area  Defined**

**Defined by physical area**

**Defined by functional area**

**Notes:**
An intersection is defined by both its physical and functional areas.  The functional area extends upstream and downstream from the physical area, which is the area of the crossing roadways.  The functional area involves the length of roadway traveled by the vehicle while the driver recognizes the intersection is being approached, a maneuver distance consisting of braking and lane changing, and a storage length to accommodate the longest queue expected.

NEXT

## Roundabouts

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

**FHWA-RD-00-067   Roundabouts:**
**	****  ****An  Informational  Guide**

**Notes:**
A section has been added to discuss the modern roundabout.  The modern roundabout is distinguished from the old-fashioned traffic circle by a requirement to yield at entry and the deflection of entering traffic.  The Green Book contains a discussion only.  The most recent reference for designing roundabouts is the FHWA report: FHWA-RD-00-067  Roundabouts:  An Informational Guide.

NEXT

## 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**

**Notes:**
The discussion on Turning Roadways has been reorganized and updated to be consistent with the design vehicles presented in Chapter 2.  The exhibits have been redrawn to illustrate the dimensions of the design vehicles.  The maximum allowable superelevation rate has been increased to 12% from 10% where climatic conditions are favorable.

NEXT

## 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**

**Notes:**
The discussion on Islands has been reorganized also.  The section on minimum design for turning roadways in the Island discussion is now incorporated into General Characteristics.  (NEXT)

The length of roadway required for reversals in curvature at divisional islands has been reduced as noted on this slide.  (NEXT)

Application at Terminals section has been replaced with Free-flow Turning Roadways.

NEXT

## Intersection Sight Distance

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

**Six  cases**

**Intersection Sight Distance**

**Notes:**
Intersection Sight Distance has been totally rewritten based on NCHRP Report 383 – Intersection Sight Distance.  The discussion covers six cases that could be involved at an intersection.  LIST

NEXT

## Gap  Acceptance

**Sight  Triangles**

- A – Approach Sight Triangles

- B – Departure Sight Triangles

- Clear Sight Triangle

- Clear Sight Triangle

- Clear Sight Triangle

- Clear Sight Triangle

**Notes:**
The basis for intersection sight distance is gap acceptance.  There is a minimum gap a driver will accept to perform a maneuver. There are two types of sight triangles considered in intersection design, approach sight triangles and departure triangles.  The area within the sight triangle must be free of obstructions that might block a driver’s view of potentially conflicting vehicles.  Each of the six cases are discussed providing exhibits with tables, graphs, equations, and time gaps as appropriate.

NEXT 

## Intersection Sight Distance

**80 km/h**

**250 m**

**170 m**

**[50 mph]**

**[840 ft]**

**[555 ft]**

**Speed**

**94 GB [90  GB]**

**2001 GB**

**ISD**

**ISD**

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

**Notes:**
As an example, for the 80 km/h [50 mph] speed, the necessary intersection sight distance is reduced as illustrated from 250 m [840 ft] to 170 m [555 ft] for Case B1 – Left turn from stop onto the major highway.

NEXT

## Offset  Left - Turn Lanes

**Advantages:**

**Better  visibility**
**Reduced  conflict**
**More  vehicles  served**

**Parallel**

**Tapered**

**Notes:**
A section including an illustration (Exhibit 9-98) has been added from research (NCHRP Report 383) to discuss offset left turn lanes.  The advantages of offsetting the left-turn are: better visibility, reduced conflict between opposing left-turn movements, and the ability to handle larger volumes of traffic in a given time period, particularly at signalized intersections.

NEXT

## Miscellaneous

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

**Notes:**
Four other areas have been modified.  The discussion of horizontal control references the discussion in Chapter3 rather than using the separate method in previous editions. (NEXT)

Deceleration length has been revised and additional design speeds and corresponding values added.  (NEXT)

The discussion on driveways has been expanded.

NEXT

## 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**

**Notes:**
Five sections of Chapter 10 – Grade Separations and Interchanges have been updated.

LIST

NEXT

## 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**

**Notes:**
The chapter contains a recommendation to separate bicycle/pedestrian movement from vehicle movement through interchange areas. (NEXT)

The Single Point Urban Interchange is discussed as a separate interchange type, rather than as a variation of the Diamond interchange.  (NEXT)

Exhibit 10-67 – Design Widths for Turning Roadways has been made consistent with Exhibit 3-55.

NEXT

## Access  Control  at  Interchanges

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

**Notes:**
A new section has been added on Access Control at Interchanges and lists four benefits of providing this access control.

Minimizes spillback on ramp and crossroad approaches to the ramp terminal,
Provides adequate distances for crossroad weaving,
Provides space for merging maneuvers, and
Provides space for storage of turning vehicles at access connections on the crossroad

NEXT

## 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 **** **

**Notes:**
The chapter also contains a caution against the use of minimum values for taper type entrances.  The values in Exhibit 10-70 which presents minimum acceleration lengths for level terrain have been recomputed.
A discussion has been added to caution designers concerning volumes exceeding lane capacity on 2-lane ramps.

NEXT

## 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”.**

**Notes:**
Discuss the identified technical corrections

## 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**”

**Notes:**
Exhibit 10-60 is actually a duplication of Exhibit 10-52.

## 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 )**

**Notes:**
There are a number of research projects underway or proposed.  The listed projects all may have impacts on future editions of the Green Book.

Mention those of interest. 

END