AASHTO Policy on Geometric Design of Highways and …axmann/Math714/TrafficCircles/Bosworth1i.pdf · FACERS Annual Conference - June 26-29, 2002 1 AASHTO Policy on Geometric Design

FACERS Annual Conference - June 26-29, 2002 1

AASHTO Policy on Geometric AASHTO Policy on Geometric Design of Highways and StreetsDesign of Highways and Streets

20012001

Highlights and Major Changes Since the 1994 Edition

Jim Mills, P.E.Roadway Design Office

605 Suwannee Street MS-32Tallahassee, FL 32399-0450850-414-4318 SC 994-4318

[email protected]


ImplementationImplementation

FHWA Adoption – NHS Highways– March 14, 2002– States will have 1 year following FHWA

Adoption to Begin Using (March 14, 2003)FDOT will use this time to review and make any necessary changes to FDOT Design Criteria and Update the PPMFlorida Greenbook – Update for 2004?


ImplementationImplementation

For Now on FDOT Projects– PPM & ’94 AASHTO In Effect– Exceptions are to be based on ’94 AASHTO

until 2001 Edition is recognized in PPM– 2001 Edition may be used as support when

documenting, justifying Design ExceptionsJanuary 2003 PPM will incorporate ‘01 AASHTO


Developed by the AASHTO Task Force on Geometric Design, including representatives from:– 18 State Departments of Transportation– Federal Highway Administration – American Public Works Association– National Association of County Engineers– National League of Cities– Port Authority of NY and NJ

DevelopmentDevelopment


FormatFormat

8.5-in x 11-in pages with soft coverSequence of chapters unchangedChapter numbers are arabic rather than Roman numeralsFigures and tables are uniformly called “exhibits” and are numbered sequentially in each chapter to reduce confusion in referencing


Units of MeasurementUnits of Measurement

Both metric and U.S. customary units are usedIn Text– Metric first, followed by U.S. customary in

square brackets: 80 km/h [50 mph]

In Exhibits– Separate exhibits for metric and U.S.

customary units are presented where needed


Units of MeasurementUnits of Measurement

Metric values are those that would be used if the policy were entirely metricU.S. customary values are those that would be used if the policy were entirely U.S. customary– Users should work entirely in one system of

measurement or the other– Do not attempt to convert values!


ResearchResearch

2001 Green Book based on latest research projects, including:– NCHRP 375 – Median Intersection Design– NCHRP 383 – Intersection Sight Distance– NCHRP 400 – Stopping Sight Distance– NCHRP 420 – Access Management– NCHRP 439 – Superelevation and Transitions– Highway Capacity Manual 2000


Additional ResearchAdditional Research

Also:– NCHRP 240 – Toll Plazas– NCHRP 241 – Truck Operating Characteristics– NCHRP 264 – Roundabouts– Transportation Research Circular 430– FHWA-RD-97-135 Older Driver Handbook– FHWA-RD-00-067 Roundabouts: An

Informational Guide


Chapter 1 Chapter 1 –– Highway FunctionsHighway Functions

No major changes


Chapter 2 Chapter 2 –– Design Controls and CriteriaDesign Controls and Criteria

New design speed definition“…a selected speed used to determine the various geometric design features of the roadway. …should be logical with respect to topography, anticipated operating speed, adjacent land use, and functional classification.”Old design speed definition “...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.” (Same wording used in Florida Greenbook)



Revised design vehicle dimensions to better reflect the existing fleetNew design vehicle turning templatesAdditional information on access control and access management, older drivers, and pedestriansCorresponding design speeds in metric and U.S. customary units are specified



Revised Dimensions for Selected Design Vehicles

90 AASHTO and FGB 01 AASHTO 90 AASHTO

and FGB 01 AASHTO 90 AASHTO and FGB 01 AASHTO

Height 4.25 4.25 13.5 11 - 13.5 13.5 13.5Width 7 7 8.5 8 8.5 8.5Length 19 19 30 30 55 55Front Overhang 3 3 4 4 3 3Rear Overhang 5 5 6 6 2 2WB 1 11 11 20 20 20 14.6WB 2 30 35.4Min Turning Radius 24 24 42 42 45 45Min Inside Radius 13.8 14.4 24.4 28.3 19.2 17

P SU WB 50


Extends range of design speeds considered– 20 to 130 km/h [15 to 80 mph]

Incorporates superelevation criteria and updates transitions and spirals based on research in NCHRP Report 439Charts for critical length of grade based on a 120 kg/kW [200 lb/hp] truck, rather than a 180 kg/kW [300 lb/hp] truck

Chapter 3 Chapter 3 –– Elements of DesignElements of Design



Revised Turning Roadway Widths based on Updated Design Vehicle Dimensions


90 AASHTO and FGB

01 AASHTO

50 23 2375 19 20

100 18 18150 17 17200 16 16300 16 15400 16 15500 15 15

Tangent 15 14

Curve

Design Widths for Turning Roadways (feet)

RADIUS To Inside of

Traveled Way Width 1-LANE Case I-C


90 AASHTO and FGB

01 AASHTO

50 25 2675 23 23

100 22 22150 21 21200 21 20300 20 20400 20 19500 20 19

Tangent 19 18

Curve


RADIUS To Inside of

Traveled Way Width1-LANE Case II - B

Provision for Passing Stalled Vehicle


90 AASHTO and FGB

01 AASHTO

50 29 2975 27 27

100 26 26150 25 24200 25 24300 24 24400 24 24500 24 24

Tangent 24 24


Curve

RADIUS To Inside of

Traveled Way Width2-LANE Case III-A

Includes 2' deduction for shoulder.



Stopping Sight Distance Criteria revised based on NCHRP Report 400– initial speed equal to design speed (no reduction to

average running speed)– based on deceleration rates for controlled braking rather

than locked-wheel braking– deceleration rate is 3.4 m/s2 [11.2 ft/s2 ], independent of

speed


Interstate Other Arterials Collectors A B C

15 8020 125 125 11525 150 150 15530 200 200 200 200 200 200 16535 225 250 250 250 225 240 220 20040 275 325 305 300 275 300 270 24045 325 400 360 375 350 325 350 325 28050 400 475 425 450 400 400 410 400 32555 450 550 495 550 500 475 450 470 450 37060 525 650 570 625 575 550 500 530 525 42065 550 725 645 700 625 600 610 550 45570 625 850 730 800 725 700 690 625 52075 82080 910

lower (FGB)

01 AASHTO Freeways

FDOT Plans Preparation ManualStopping Sight Distance

RRRNew/Reconstr

90 AASHTO

upperDesign Speed



Stopping Sight Distance

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60 70 80 90Design Speed - mph

Stop

ping

Sig

ht D

ista

nce

- Fee

t

90 AASHTO lower

01 AASHTO

PPM Freeways Interstate

PPM New/Reconstr Arterials

PPM RRR C



Vertical Curve Design Criteria revised based on NCHRP Report 400– driver eye height: 1,080 mm [3.5 ft], rather

than 1,070 mm [3.5 ft]– object height: 600 mm [2.0 ft], which

represents vehicle tail light height, rather than 150 mm [6 in], which represented an arbitrary object height

Improved discussion of sight distance at undercrossings


Vertical Curve Design CriteriaVertical Curve Design Criteria

Eye Height

’90 AASHTO/FGB = 3.5’

’01 AASHTO = 3.5’

Object Height

’90 AASHTO/FGB = 6”

’01 AASHTO = 2.0’



15 320 10 10 725 20 20 1230 30 30 19 30 30 30 30 2035 40 50 29 50 40 43 36 3040 60 80 44 70 60 68 55 4345 80 120 61 110 90 80 92 79 5950 110 120 160 84 150 130 120 126 120 7955 150 220 114 220 190 170 150 166 152 10360 190 310 151 300 250 230 190 211 207 13365 230 400 193 380 320 280 230 280 228 15670 290 540 247 500 400 370 358 294 20375 31280 384

Design Speed lower

FGB upperFreeways

K Value - Crest Vertical Curves90 AASHTO PPM

New and Reconstr RRR01 AASHTO


K Value - Crest Vertical Curves

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70 80 90

Design Speed - mph

K-V

alue

- C

rest

Ver

t Cur

ves

90 AASHTO lower

01 AASHTO


PPM New and Reconstr Arterials

PPM RRR C



15 1020 20 20 1725 30 30 2630 40 40 37 40 40 36 36 2835 50 50 49 50 50 46 41 3640 60 70 64 60 60 62 54 4645 70 90 79 80 80 70 75 69 5750 90 110 96 100 90 90 92 89 6955 100 130 115 130 120 110 100 108 103 8160 120 160 136 150 140 130 120 125 123 9465 130 180 157 170 160 150 130 147 130 10470 150 220 181 200 180 170 169 151 12275 20680 231

Freeways New and Reconstr RRR01 AASHTOlower (FGB) upper

K Value - Sag Vertical Curves

Design Speed

90 AASHTO PPM


K Value - Sag Vertical Curves

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80 90

Design Speed mph

K V

alue

- S

ag V

ert C

urve

s

90 AASHTO lower

01 AASHTO


PPM New and Reconstr Arterials

PPM RRR C


Chapter 4 Chapter 4 –– Cross Section ElementsCross Section Elements

Curb terminology changed– “vertical curb” replaces “barrier curb”– “sloping curb” replaces “mountable curb”

NOTE:FDOT Type F and Type E curb meet the AASHTO definition for Sloping Curb.


Chapter 4 Chapter 4 –– Cross Section ElementsCross Section Elements

Eliminates material on parabolic cross sectionsDiscusses sidewalk curb ramps and ADA complianceIncorporates research on median width and median opening design from NCHRP Report 375


Chapter 5 Chapter 5 –– Local Roads and StreetsLocal Roads and Streets

Includes discussions of:– ADA compliance– new AASHTO bicycle guide– proposed AASHTO pedestrian guide

(currently in preparation)Refers to forthcoming AASHTO report– Guidelines for Geometric Design of Very Low

Volume Local Roads (< 400 ADT)


Chapter 6 Chapter 6 –– Collector Roads and StreetsCollector Roads and Streets

Includes discussions of:– ADA compliance– new AASHTO bicycle guide– proposed AASHTO pedestrian guide

Eliminates material on parabolic cross sections


Chapter 6 Chapter 6 –– Collector Roads and StreetsCollector Roads and Streets

Incorporates research on median width and median opening design from NCHRP Report 375Incorporates revised discussions of:– traffic control devices– erosion control


Chapter 7 Chapter 7 –– Rural and Urban ArterialsRural and Urban Arterials

Incorporates research on median width and median opening design from NCHRP Report 375Incorporates research on access management from NCHRP Report 420Places more emphasis on design to accommodate pedestrians and bicycles in the arterial environment


Chapter 8 Chapter 8 –– FreewaysFreeways

No major changes


Chapter title changed from“At-Grade Intersections”Explicitly defines the functional area of an intersection– includes the distance a vehicle travels during

perception-reaction and maneuvering (braking and lane changing), and the space needed for storage (to accommodate the longest queue expected most often)

Chapter 9 Chapter 9 –– IntersectionsIntersections



Includes discussions of:– access management near intersections– modern roundabouts

Includes expanded discussion of offset left-turn lanes– advantages include better visibility, reduced

conflicts and the ability to serve more vehicles.



Includes revised intersection sight distance criteria based on NCHRP Report 383– revised criteria for uncontrolled intersections– new gap acceptance criteria for entering or

crossing major roads– limited sight distances for signals and all-way

stops


Intersection Sight DistanceIntersection Sight DistanceLength of SD Leg Along Major Road

Major Road

a = driver eye setback

1990 AASHTO: a = 20’

Florida Greenbook: a = 15’

2001 AASHTO: a = 17.8' desirablea = 14.4' minimum

a

Length of SD Leg Along Major Road

Min

or R

oad

Sight LineSight Line


Left and Right Turn

15 170 14520 225 19525 280 24030 380 300 335 29035 470 350 390 33540 580 400 445 38545 710 450 500 43050 840 500 555 48055 990 550 610 53060 1150 600 665 57565 1350 650 720 62570 700 775 67075 830 72080 885 765

Length of Sight Distance Leg along Major Road

Left Turn Maneuver

01 AASHTO - 2 Lane Intersection -

Design SpeedIndex 546 and 90

AASHTO Right Turn & Crossing Maneuver

Florida Greenbook W = 50' - based on

Crossing Maneuver


Intersection Sight Distance

0

200

400

600

800

1000

1200

1400

1600

0 10 20 30 40 50 60 70 80 90Design Speed - mph

Leng

th o

f Sig

ht D

ista

nce

Leg

Fee

t

Index 546 and 90 AASHTO

Florida Greenbook W = 50' - basedon Crossing Maneuver

01 AASHTO - 2 Lane Intersection -Left Turn Maneuver

01 AASHTO - 2 Lane Intersection -Right Turn & Crossing Maneuver


Chapter 10 Chapter 10 –– Grade Separations and Grade Separations and InterchangesInterchanges

Places more emphasis on design to accommodate pedestrians and bicycles at interchangesIncludes expanded discussion of Single Point Urban Interchanges (SPUIs)Increases emphasis on access management on interchange crossroads


Chapter 10 Chapter 10 –– Grade Separations and Grade Separations and InterchangesInterchanges

Expands discussion of superelevation and cross slope within interchangesAddresses two-lane entrance ramps


AASHTO Policy on Geometric Design of AASHTO Policy on Geometric Design of Highways and Streets 2001Highways and Streets 2001

Where to Get Copies:

AASHTOP.O. Box 96716Washington, DC 20090-6716Phone 1-800-231-3475 Fax 1-800-525-5562Online www.transportation.orgNot available from FDOT


Price as of June 20, 2002– BOOK • ITEM NO. GDHS-4

• Price per copy $102• AASHTO Members $80

– CD-ROM • ITEM NO. GDHS-4-CD• Price per copy $165 • AASHTO Members $130

– BOOK & CD-ROM • ITEM NO. GDHS-4-COM• Price per copy $248• AASHTO Members $195

AASHTO Policy on Geometric Design of AASHTO Policy on Geometric Design of Highways and Streets 2001Highways and Streets 2001


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

Price as of June 20, 2002– BOOK • ITEM NO. VLVLR-1

• Price per copy $35.00• AASHTO Members $30.00• NACE Members may purchase at AASHTO Member

price. (Must indicate membership when ordering.)


Florida Green Book Florida Green Book -- May 2002May 2002

Adopted by Rule Effective July 9, 2002– Includes new chapters on traffic calming and

residential street design

Full Document posted on the FDOT Roadway Design Office Web Site– http://www11.myflorida.com/rddesign/

Hardcopies to be available in about 30 days.


QUESTIONS?QUESTIONS?

Jim Mills, P.E.Roadway Design Office605 Suwannee Street MS-32Tallahassee, FL 32399-0450850-414-4318 SC [email protected]

AASHTO Policy on Geometric Design of Highways and …axmann/Math714/TrafficCircles/Bosworth1i.pdf · FACERS Annual Conference - June 26-29, 2002 1 AASHTO Policy on Geometric Design

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