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Geometric Design of
Highways and Streets2004
American Association of State Highwayand Transportation Officials
APOL
ICY
ON
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A Policy onGeometric Design of
Highways and Streets
2004Fifth Edition
American Association of State
Highway and Transportation Officials
444 North Capitol Street, N.W., Suite 249
Washington, D.C. 20001
(202) 624-5800
www.transportation.org
Copyright 2004, by the American Association of State Highway and
Transportation Officials. All Rights Reserved. This book, or parts thereof, may
not be reproduced in any form without written permission of the publisher.
Printed in the United States of America.
ISBN: 1-56051-263-6
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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American Association of State Highwayand Transportation Officials
Executive Commit tee20042005
VOTING MEMBERS
OFFICERS:
PRESIDENT: Bryan Nicol, Indiana
VICE PRESIDENT: Jack Lettiere, New Jersey
SECRETARY-TREASURER: Larry King, Pennsylvania
REGIONAL REPRESENTATIVES:
REGION I: Allen Biehler, Pennsylvania, One-Year Term
Dan Tangherlini, District of Columbia, Two-Year Term
REGION II: Fernando Fagundo, Puerto Rico, One-Year Term
Harold Linnenkohl, Georgia, Two-Year Term
REGION III: Gloria Jeff, Michigan, One-Year Term
Frank Busalacchi, Wisconsin, Two-Year Term
REGION IV: Tom Norton, Colorado, One-Year Term
David Sprynczynatyk, Two-Year Term
NON-VOTING MEMBERS
IMMEDIATE PAST PRESIDENT: John Njord, Utah
EXECUTIVE DIRECTOR: John Horsley, Washington, D. C.
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Task Force on Geometric Design 2004
Region 1:
Kenneth Briggs Maryland
Donald A. Lyford New Hampshire Phillip J. Clark New York
Reza Maleki Port Authority of New York and New Jersey
Region 2:
Don T. Arkle Alabama
Robert L. Walters (Chair) Arkansas
John Pickering Mississippi
Jeff Jones Tennessee
Norman H. Roush West Virginia
Region 3:
James O. Brewer Kansas
Jim Rosenow Minnesota
Ted Watson Nebraska
Larry Sutherland Ohio
Region 4:
Karla Sutliff California
Max Valerio New Mexico
Wayne Kinder Nevada
Reza Amini Oklahoma
Mark A. Marek Texas
Paul Bercich Wyoming
Other:
Jim McDonnell AASHTO Liaison
John LaPlante American Public Works Association
William Prosser FHWA
Joe Ruffer National Association of County Engineers
David Hutchison National League of Cities
Ray Derr TRB
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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DISTRICT OF
COLUMBIA:
Penney, Kathleen
Supervisory Civil Engineer
District of Columbia Department ofTransportation
64 New York Avenue, N.E.
Washington, DC 20002
FLORIDA: Blanchard, Brian A.
State Roadway Design EngineerFlorida Department of Transportation605 Suwannee Street
Tallahassee, FL 32399-0450
Mills, Jim
Roadway Design EngineerFlorida Department of Transportation
605 Suwannee Street
Tallahassee, FL 32399-0450
Greer, Robert
Director, Office of Design
Florida Department of Transportation605 Suwannee Street, MS 38
Tallahassee, FL 32311-0450
GEORGIA: Buchan, James (Ben)
State Road and Airport Design EngineerGeorgia Department of Transportation
2 Capitol Square, S.W., Room 356Atlanta, GA 30334
Turner, Thomas L.
Georgia Department of Transportation
2 Capitol Square, S.W., Room 129Atlanta, GA 30334
HAWAII: Choy, GaryEngineer Program Manager, Design
Branch, Highways Division
Hawaii Department of Transportation
601 Kamokila Boulevard, Room 688AKapolei, HI 96707
Fronda, Julius
Highway Design Engineer
Hawaii Department of Transportation
601 Kapolei Boulevard, Room 609
Kapolei, HI 96707
IDAHO: Hutchinson, Steven C.Assistant Chief Engineer, Development
Idaho Transportation Department
P.O. Box 7129, 3311 W. State Street
Boise, ID 83707-1129
Thomas, Loren D.Roadway Design Engineer
Idaho Transportation Department
P.O. Box 7129, 3311 W. State Street
Boise, ID 83707-1129
ILLINOIS: Hine, MichaelChief of Design and Environment
Illinois Department of Transportation
2300 S. Dirksen Parkway
Springfield, IL 62764
INDIANA: Mroczka, Gerald
Chief, Division of DesignIndiana Department of Transportation
100 N. Senate Avenue, Room N-642
Indianapolis, IN 46204-2217
IOWA: Kennerly, Michael J.
Director, Office of Design
Iowa Department of Transportation
800 Lincoln WayAmes, IA 50010-6915
Little, David
District Engineer, District 2
Iowa Department of Transportation,Engineering Division1420 Fourth Street, S.E.
Mason City, IA 50402-0742
Stein, Will
Methods Engineer
Iowa Department of Transportation800 Lincoln Way
Ames, IA 50010-6915
KANSAS: Adams, Richard G.
Road Design Engineer
Kansas Department of Transportation
915 Harrison Ave., 9th FloorTopeka, KS 66612-1568
Brewer, James O.
Engineering Manager, State Road OfficeKansas Department of Transportation
Docking State Office Building, 9th Floor
Topeka, KS 66612-1568
Armstrong, LaMonte C.
Road Design Engineer
Kansas Department of Transportation
Docking State Office Building, 9th Floor
Topeka, KS 66612-1568
KENTUCKY: Sharpe, Gary W.Director, Division of Highway Design
Kentucky Transportation Cabinet
200 Mero Street
Frankfort, KY 40622
Jones, David
Location Branch ManagerKentucky Transportation Cabinet
200 Mero Street
Frankfort, KY 40622
Sperry, Kenneth R.Assistant State Highway Engineer
Kentucky Transportation Cabinet, Officeof Project Development
200 Mero Street
Frankfort, KY 40622
LOUISIANA: Israel, N. KentRoadway Design Administrator
Louisiana Department of Transportation
and Development
P.O. Box 94245, 1201 Capitol
Access RoadBaton Rouge, LA 70804-9245
Kalivoda, Nicholas
Traffic Engineering Development
Administrator
Louisiana Department of Transportation
and Development
P.O. Box 94245, 1201 CapitolAccess Road
Baton Rouge, LA 70804-9245
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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LOUISIANA: Porta, Lloyd E.
Project Development Engineer
Louisiana Department of Transportationand Development
P.O. Box 94245, 1201 Capitol
Access Road
Baton Rouge, LA 70804-9245
MAINE: Casey, Jerry A.Program Manager, Urban and ArterialHighways
Maine Department of TransportationTransportation Building, State
House Station 16Augusta, ME 04333-0016
MARYLAND: Douglass, Robert D.
Director, Woodrow Wilson
Bridge ProjectMaryland Department of Transportation,
State Highway Administration
707 N. Calvert Street, Mail Stop C102
Baltimore, MD 21202
McClelland, Kirk G.
Director, Office of HighwayDevelopment
Maryland Department of Transportation,
State Highway Administration
707 N. Calvert Street
Baltimore, MD 21202
MASSACHUSETTS: Blundo, JohnDeputy Chief Engineer, Projects
Division
Massachusetts Highway Department
10 Park Plaza, Room 6340Boston, MA 02116-3973
Wood, StanleyHighway Design Engineer
Massachusetts Highway Department
10 Park Plaza
Boston, MA 02116
MICHIGAN: Van Port Fleet, Mark
Engineer of Design
Michigan Department of Transportation,
Design Division
State Transportation Building425 W. Ottawa Street, P.O. Box 30050
Lansing, MI 48909
MINNESOTA: Elasky, Richard A.
Director, Office of Environmental
Services
Minnesota Department of TransportationTransportation Building, MS 620,
395 John Ireland Boulevard
St. Paul, MN 55155-1899
Thakur, Mukhtar
State Design EngineerMinnesota Department of Transportation
Transportation Building, MS 610,
395 John Ireland Boulevard
St. Paul, MN 55155-1899
MISSISSIPPI: Pickering, John B.
Roadway Design Engineer
Mississippi Department of Transportation
P.O. Box 1850, 401 North West StreetJackson, MS 39215-1850
Foster, David
Assistant Chief Engineer, Preconstruction
Mississippi Department of TransportationP.O. Box 1850, 401 North West StreetJackson, MS 39215-1850
Purvis, Keith
Assistant Roadway Design Engineer
Mississippi Department of Transportation
P.O. Box 1850, 401 North West StreetJackson, MS 39215-1850
MISSOURI: Heckemeyer, DianeState Design Engineer
Missouri Department of Transportation
P.O. Box 270
Jefferson City, MO 65102-0207
Nichols, David B.
Director of Project Development
Missouri Department of Transportation105 West Capitol Avenue, P.O. Box 270
Jefferson City, MO 65102-0207
MONTANA: Peil, Carl S.Preconstruction Engineer
Montana Department of Transportation
P.O. Box 201001, 2701 Prospect Avenue
Helena, MT 59620-1001
Ferry, Paul R.
Montana Department of TransportationP.O. Box 201001, 2701 Prospect Avenue
Helena, MT 59620-1001
Williams, Ronald E.
Road Design Engineer
Montana Department of Transportation
P.O. Box 201001, 2701 Prospect AvenueHelena, MT 59620-1001
NEBRASKA: Poppe, Eldon D.
Engineer, Roadway Design Division
Nebraska Department of Roads1500 Nebraska Highway 2
P.O. Box 94759Lincoln, NE 68509-4759
Allyn, Dawn
Assistant Design Engineer
Nebraska Department of Roads1500 Nebraska Highway 2
P.O. Box 94759
Lincoln, NE 68509-4759
Turek, DonAssistant Design Engineer
Nebraska Department of Roads1500 Nebraska Highway 2
P.O. Box 94759
Lincoln, NE 68509-4759
NEVADA: Kinder, Wayne
Chief Road Design Engineer
Nevada Department of Transportation
1263 S. Stewart StreetCarson City, NV 89712-0002
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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PUERTO RICO: Prez, Ariel
Director, Design Area
Puerto Rico Highway and TransportationAuthority
P.O. Box 42007, Minillas Station
San Juan, PR 00940-2007
Santana-Pimentel, Jos
Puerto Rico Highway and TransportationAuthorityP.O. Box 42007, Minillas Station
San Juan, PR 00940-2007
RHODE ISLAND: Bennett, J. Michael
Deputy Chief Engineer, Environmentaland Intermodal Planning
Rhode Island Department of
Transportation
State Office Building, 2 Capitol HillProvidence, RI 02903-1124
SOUTHCAROLINA:
Kneece, Rocque L.Program Development Engineer, East
South Carolina Department of
Transportation
Silas N. Pearman Building,955 Park Street,
P.O. Box 191
Columbia, SC 29202-0191
Pratt, Robert I.
Director of Preconstruction
South Carolina Department ofTransportation
Silas N. Pearman Building,
955 Park Street,
P.O. Box 191Columbia, SC 29202-0191
Walsh, John V.Deputy State Highway Engineer
South Carolina Department of
Transportation
Silas N. Pearman Building,955 Park Street,
P.O. Box 191
Columbia, SC 29202-0191
SOUTH DAKOTA: Gengler, Joel
Chief Road Design EngineerSouth Dakota Department of
Transportation
700 East Broadway Avenue
Pierre, SD 57501-2586
Feller, Joe
Chief Materials and Surfacing EngineerSouth Dakota Department of
Transportation
700 East Broadway Avenue
Pierre, SD 57501-2586
TENNESSEE: Jones, Jeff C.Director, Design Division
Tennessee Department of Transportation
James K. Polk Building, Suite 1300
505 Deaderick Street
Nashville, TN 37243-0339
TENNESSEE: Zeigler, James
Director, Bureau of Planning and
Development
Tennessee Department of TransportationJames K. Polk Building, Suite 700
505 Deaderick Street
Nashville, TN 37243-0339
TEXAS: Bohuslav, KenDirector, DesignTexas Department of Transportation
125 East 11th Street
Austin, TX 78701-2483
Marek, Mark
Engineer of Roadway DesignTexas Department of Transportation
125 East 11th Street
Austin, TX 78701-2483
UTAH: Davis, Jason E.
Engineering Services Director
Utah Department of Transportation4501 South 2700 West
P.O. Box 148490
Salt Lake City, UT 84119
VERMONT: Shattuck, Robert F.
Roadway Design Program Manager
Vermont Agency of TransportationNational Life Building, Drawer 33
Montpelier, VT 05633-5001
VIRGINIA: Mirshahi, Mohammad
Location and Design Division
AdministratorVirginia Department of Transportation
1401 E. Broad Street
Richmond, VA 23219
WASHINGTON: Albin, Richard
Assistant State Design Engineer, NWRegion
Washington State Department ofTransportation
Transportation Building
310 Maple Park, P.O. Box 47329Olympia, WA 98504-7329
Peterfeso, Harold
State Design Engineer
Washington State Department of
Transportation
Transportation Building310 Maple Park
P.O. Box 47329
Olympia, WA 98504-7300
WEST VIRGINIA: Clevenger, David E.
Consultant Review Section HeadWest Virginia Department of
Transportation, Engineering Division1900 Kanawha Boulevard East,
Building 5
Charleston, WV 25305-0440
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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WEST VIRGINIA: Epperly, Randolph T.
Deputy State Highway Engineer, Project
DevelopmentWest Virginia Department of
Transportation
1900 Kanawha Boulevard East,
Building 5Charleston, WV 25305-0440
Roush, Norman H.Deputy Secretary/Deputy Commissioner
West Virginia Department ofTransportation
1900 Kanawha Boulevard East,Building 5
Charleston, WV 25305-0440
WISCONSIN: Cannestra, Beth
Acting Director, Bureau of HighwayDevelopment
Wisconsin Department of Transportation
P.O. Box 7916
Madison, WI 53707-7916
Pfeiffer, Robert F.
Project Development ChiefWisconsin Department of Transportation,
District 2, Waukesha
P.O. Box 798
Waukesha, WI 53187-0798
WYOMING: Bercich, Paul
Highway Development EngineerWyoming Department of Transportation
P.O. Box 1708, 5300 Bishop Boulevard
Cheyenne, WY 82003-1708
U.S. Department o f Transpor tation Member
FEDERAL
AVIATIONADMINISTRA-
TION:
Marinelli, RickManager, Airport Engineering division
Federal Aviation Administration
Room 616C, AAS-200
800 Independence Avenue, S.W.Washington, DC 20591-0001
Associate MemberBridge, Por t, and Tol l
NEW JERSEY
TURNPIKE
AUTHORITY:
Williams, J. Lawrence
Supervising Engineer, Highways
New Jersey Turnpike Authority
Administrative BuildingP.O. Box 1121
New Brunswick, JN 08903-1121
PENNSYLVANIATURNPIKE
COMMISSION:
Troup, Barry L.Assistant Chief Engineer, Design
Pennsylvania Turnpike CommissionP.O. Box 67676
Harrisburg, PA 17106-7676
PORT AUTHORITY
OF NEW YOK AND
NEW JERSEY:
Chen, Yue Sun
Chief Civil Engineer
Port Authority of New York andNew Jersey
2 Gateway Center, Room 16NW
Newark, NJ 07102
Assoc iate MemberFederal
USDA FORESTSERVICE:
Beighley, DeborahNational Transportation Planning
Program Engineer
USDA Forest ServiceMail Stop 1101
1400 Independence Avenue, S.W.Washington, DC 20250-1101
Associate MembersInternational
ALBERTA,
CANADA:
Kwan, Allan
Executive Director, TechnicalStandards Branch
Alberta Transportation, 2ndFloor
4999 98thAvenue
Edmonton, AB T6B 2X3
BRITISHCOLUMBIA,
CANADA:
Voyer, RichardSenior Standards and Design Engineer
British Columbia Ministry of
Transportation and Highways
5B 940 Blanshard StreetVictoria, British Columbia V8W 3E6
ONTARIO,
CANADA:
Bucik, Joe
Manager, Highway Design Office
Ontario Ministry of Transportation
Engineering Standards Branch
Garden City Tower, 2
nd
Floor, 2N036301 St. Paul StreetSt. Catherines, ON L2R 7R4
SASKATCHEWAN,
CANADA:
Kent, Sudhy
Director, Design and Traffic Operations
Saskatchewan Highways and
Transportation1630 Park, 2ndFloorRegina, SK S4P 3V7
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Preface
This Policy was developed as part of the continuing work of the Standing Committee onHighways. The Committee, then titled the Committee on Planning and Design Policies, was
established in 1937 to formulate and recommend highway engineering policies. This Committee
has developed A Policy on Geometric Design of Rural Highways, 1954 and 1965 editions; A
Policy on Arterial Highways in Urban Areas, 1957;A Policy on Design of Urban Highways and
Arterial Streets, 1973; Geometric Design Standards for Highways Other Than Freeways, 1969;A
Policy on Geometric Design of Highways and Streets, 1984, 1990, 1994, and 2001; A Policy on
Design StandardsInterstate System, 1956, 1967, and 1991; and a number of other AASHO and
AASHTO policy and guide publications.
An AASHTO publication is typically developed through the following steps: (1) The
Committee selects subjects and broad outlines of material to be covered. (2) The appropriatesubcommittee and its task forces, in this case, the Subcommittee on Design and its Task Force on
Geometric Design, assemble and analyze relevant data and prepare a tentative draft. Working
meetings are held and revised drafts are prepared, as necessary, and reviewed by the
Subcommittee, until agreement is reached. (3) The manuscript is then submitted for approval by
the Standing Committee on Highways and then the Executive Committee. Standards and policies
must be adopted by a two-thirds vote by the Member Departments before publication. During the
developmental process, comments are sought and considered from all the states, the Federal
Highway Administration, and representatives of the American Public Works Association, the
National Association of County Engineers, the National League of Cities, and other interested
parties.
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Chapter 2
Design Controls and Criteria
Introduction .........................................................................................................................................15
Design Vehicles................................................................................................................................... 15
General Characteristics .............................................................................................................. 15
Minimum Turning Paths of Design Vehicles.............................................................................18
Vehicle Performance.................................................................................................................. 43
Vehicular Pollution ....................................................................................................................43
Driver Performance ............................................................................................................................. 46
Introduction................................................................................................................................46
Older Drivers .............................................................................................................................47
The Driving Task .......................................................................................................................47
The Guidance Task ....................................................................................................................48
Lane Placement and Road Following...............................................................................48
Car Following...................................................................................................................48
Passing Maneuvers ...........................................................................................................49
Other Guidance Activities ................................................................................................49
The Information System.............................................................................................................49
Traffic Control Devices....................................................................................................49
The Roadway and Its Environment ..................................................................................49
Information Handling.................................................................................................................50
Reaction Time ..................................................................................................................50
Primacy............................................................................................................................. 53
Expectancy .......................................................................................................................53
Driver Error................................................................................................................................ 53
Errors Due to Driver Deficiencies ....................................................................................54
Errors Due to Situation Demands .....................................................................................56
Speed and Design.......................................................................................................................56
Design Assessment ....................................................................................................................57
Traffic Characteristics .........................................................................................................................58
General Considerations.............................................................................................................. 58
Volume.......................................................................................................................................58
Average Daily Traffic.......................................................................................................58
Peak-Hour Traffic.............................................................................................................59
Directional Distribution .............................................................................................................62
Composition of Traffic...............................................................................................................63
Projection of Future Traffic Demands .......................................................................................65
Speed..........................................................................................................................................66
Operating Speed ...............................................................................................................66
Running Speed..................................................................................................................67
Design Speed....................................................................................................................67
Traffic Flow Relationships.........................................................................................................72
Highway Capacity ...............................................................................................................................74
General Characteristics ..............................................................................................................74
Application.................................................................................................................................74
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Capacity as a Design Control..................................................................................................... 75
Design Service Flow Rate Versus Design Volume .......................................................... 75
Measures of Congestion................................................................................................... 75
Relation between Congestion and Traffic Flow Rate....................................................... 76
Acceptable Degrees of Congestion .................................................................................. 77
Principles for Acceptable Degrees of Congestion ............................................................ 78Reconciliation of Principles for Acceptable Degrees of Congestion ............................... 80
Factors Other than Traffic Volume That Affect Operating Conditions .....................................81
Highway Factors .............................................................................................................. 81
Alignment......................................................................................................................... 82
Weaving Sections............................................................................................................. 82
Ramp Terminals............................................................................................................... 82
Traffic Factors.................................................................................................................. 83
Peak Hour Factor.............................................................................................................. 83
Levels of Service ....................................................................................................................... 84
Design Service Flow Rates ........................................................................................................ 85
Weaving Sections............................................................................................................. 85Multilane Highways without Access Control................................................................... 86
Arterial Streets and Urban Highways ............................................................................... 86
Intersections ..................................................................................................................... 88
Pedestrians and Bicycles .................................................................................................. 88
Access Control and Access Management............................................................................................ 88
General Conditions .................................................................................................................... 88
Basic Principles of Access Management ................................................................................... 90
Access Classifications................................................................................................................ 90
Methods of Controlling Access ................................................................................................. 91
Benefits of Controlling Access .................................................................................................. 91
The Pedestrian..................................................................................................................................... 96General Considerations.............................................................................................................. 96
General Characteristics .............................................................................................................. 96
Walking Speeds ......................................................................................................................... 97
Walkway Capacities .................................................................................................................. 98
Sidewalks ......................................................................................................................... 98
Intersections ..................................................................................................................... 99
Reducing Pedestrian-Vehicular Conflicts ........................................................................ 99
Characteristics of Persons with Disabilities............................................................................... 99
Mobility Impairments..................................................................................................... 100
Visual Impairments ........................................................................................................ 100
Developmental Impairments .......................................................................................... 100Bicycle Facilities............................................................................................................................... 100
Safety................................................................................................................................................. 101
Environment...................................................................................................................................... 106
Economic Analysis............................................................................................................................ 106
References......................................................................................................................................... 106
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Chapter 3
ELEMENTS OF DESIGN
Introduction .......................................................................................................................................109
Sight Distance....................................................................................................................................109
General Considerations............................................................................................................109
Stopping Sight Distance...........................................................................................................110
Brake Reaction Time......................................................................................................110
Braking Distance ............................................................................................................111
Design Values.................................................................................................................113
Effect of Grade on Stopping...........................................................................................113
Variation for Trucks .......................................................................................................114
Decision Sight Distance...........................................................................................................115
Passing Sight Distance for Two-Lane Highways.....................................................................118
Criteria for Design..........................................................................................................118
Design Values.................................................................................................................122
Effect of Grade on Passing Sight Distance.....................................................................125
Frequency and Length of Passing Sections .................................................................... 125
Sight Distance for Multilane Highways ................................................................................... 126
Criteria for Measuring Sight Distance .....................................................................................127
Height of Drivers Eye ...................................................................................................127
Height of Object ............................................................................................................. 127
Sight Obstructions ..........................................................................................................128
Measuring and Recording Sight Distance on Plans........................................................128
Horizontal Alignment........................................................................................................................131
Theoretical Considerations....................................................................................................... 131
General Considerations............................................................................................................132
Superelevation................................................................................................................132
Side Friction Factor ........................................................................................................133
Distribution of eandfover a Range of Curves ..............................................................140
Design Considerations .............................................................................................................143
Normal Cross Slope........................................................................................................143
Sharpest Curve without Superelevation..........................................................................144
Maximum Superelevation Rates for Streets and Highways............................................144
Maximum Superelevation for Turning Roadways..........................................................145
Minimum Radius............................................................................................................146
Effects of Grades ............................................................................................................ 148
Design for Low-Speed Urban Streets.......................................................................................148
Side Friction Factors.......................................................................................................148
Superelevation................................................................................................................149
Sharpest Curve without Superelevation..........................................................................149
Design for Rural Highways, Urban Freeways, and High-Speed Urban Streets .......................153
Side Friction Factors.......................................................................................................153
Superelevation................................................................................................................153
Procedure for Development of Method 5 Superelevation Distribution .......................... 153
Turning Roadways ...................................................................................................................163
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Design Speed.................................................................................................................. 164
Use of Compound Curves .............................................................................................. 164
Design Superelevation Tables.................................................................................................. 165
Sharpest Curve without Superelevation ......................................................................... 166
Transition Design Controls...................................................................................................... 175
General Considerations .................................................................................................. 175Tangent-to-Curve Transition.......................................................................................... 176
Spiral Curve Transitions................................................................................................. 184
Length of Spiral.............................................................................................................. 185
Compound Curve Transition.......................................................................................... 192
Methods of Attaining Superelevation............................................................................. 192
Design of Smooth Profiles for Traveled Way Edges...................................................... 196
Axis of Rotation with a Median ..................................................................................... 197
Minimum Transition Grades .......................................................................................... 198
Transitions and Compound Curves for Turning Roadways ........................................... 199
Length of Spiral for Turning Roadways......................................................................... 200
Compound Circular Curves............................................................................................ 201Offtracking............................................................................................................................... 202
Derivation of Design Values for Widening on Horizontal Curves................................. 202
Traveled Way Widening on Horizontal Curves....................................................................... 208
Design Values for Traveled Way Widening................................................................... 210
Application of Widening on Curves............................................................................... 214
Widths for Turning Roadways at Intersections........................................................................ 216
Design Values ................................................................................................................ 219
Widths Outside Traveled Way ....................................................................................... 222
Sight Distance on Horizontal Curves....................................................................................... 224
Stopping Sight Distance................................................................................................. 224
Passing Sight Distance ................................................................................................... 228General Controls for Horizontal Alignment ............................................................................ 229
Vertical Alignment............................................................................................................................ 231
Terrain ..................................................................................................................................... 231
Grades...................................................................................................................................... 231
Vehicle Operating Characteristics on Grades................................................................. 232
Control Grades for Design ............................................................................................. 233
Critical Lengths of Grade for Design ............................................................................. 236
Climbing Lanes........................................................................................................................ 241
Climbing Lanes for Two-Lane Highways ...................................................................... 241
Climbing Lanes on Freeways and Multilane Highways................................................. 247
Methods for Increasing Passing Opportunities on Two-Lane Roads....................................... 250Passing Lanes................................................................................................................. 250
Turnouts ......................................................................................................................... 253
Shoulder Driving............................................................................................................ 254
Shoulder Use Sections.................................................................................................... 255
Emergency Escape Ramps....................................................................................................... 255
General ........................................................................................................................... 255
Need and Location for Emergency Escape Ramps ........................................................ 257
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Types of Emergency Escape Ramps...............................................................................258
Design Considerations....................................................................................................260
Brake Check Areas .........................................................................................................265
Maintenance ...................................................................................................................265
Vertical Curves ........................................................................................................................265
General Considerations...................................................................................................265Crest Vertical Curves......................................................................................................267
Sag Vertical Curves........................................................................................................273
Sight Distance at Undercrossings...................................................................................277
General Controls for Vertical Alignment ....................................................................... 279
Combinations of Horizontal and Vertical Alignment ........................................................................280
General Considerations............................................................................................................280
General Design Controls..........................................................................................................281
Alignment Coordination in Design ..........................................................................................282
Other Elements Affecting Geometric Design .................................................................................... 283
Drainage...................................................................................................................................286
Erosion Control and Landscape Development .........................................................................288Rest Areas, Information Centers, and Scenic Overlooks .........................................................289
Lighting....................................................................................................................................290
Utilities.....................................................................................................................................292
General ...........................................................................................................................292
Urban..............................................................................................................................293
Rural ............................................................................................................................... 293
Traffic Control Devices............................................................................................................ 294
Signing and Marking ......................................................................................................294
Traffic Signals ................................................................................................................ 295
Noise Barriers ..........................................................................................................................296
Fencing.....................................................................................................................................296Maintenance of Traffic through Construction Areas................................................................297
References .........................................................................................................................................299
Chapter 4
Cross Section Elements
General ..............................................................................................................................................305
Pavement ...........................................................................................................................................305
Surface Type ............................................................................................................................ 305
Cross Slope .............................................................................................................................. 305
Skid Resistance ........................................................................................................................310
Lane Widths....................................................................................................................................... 311
Shoulders...........................................................................................................................................312
General Characteristics ............................................................................................................312
Width of Shoulders ..................................................................................................................314
Shoulder Cross Sections...........................................................................................................315
Shoulder Stability.....................................................................................................................317
Shoulder Contrast.....................................................................................................................318
Turnouts ...................................................................................................................................318
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Horizontal Clearance to Obstructions ............................................................................................... 318
Curbs ................................................................................................................................................. 319
General Considerations............................................................................................................ 319
Curb Configurations ................................................................................................................ 320
Curb Placement........................................................................................................................ 322
Drainage Channels and Sideslopes.................................................................................................... 323General Considerations............................................................................................................ 323
Drainage Channels................................................................................................................... 323
Sideslopes ................................................................................................................................ 326
Illustrative Outer Cross Sections....................................................................................................... 329
Normal Crown Sections........................................................................................................... 329
Superelevated Sections ............................................................................................................ 330
Traffic Barriers.................................................................................................................................. 331
General Considerations............................................................................................................ 331
Longitudinal Barriers............................................................................................................... 333
Roadside Barriers........................................................................................................... 333
Median Barriers.............................................................................................................. 334Bridge Railings........................................................................................................................ 335
Crash Cushions ........................................................................................................................ 336
Medians............................................................................................................................................. 337
Frontage Roads.................................................................................................................................. 339
Outer Separations.............................................................................................................................. 342
Noise Control .................................................................................................................................... 344
General Considerations............................................................................................................ 344
General Design Procedures...................................................................................................... 345
Noise Reduction Designs......................................................................................................... 346
Roadside Control............................................................................................................................... 348
General Considerations............................................................................................................ 348Driveways................................................................................................................................ 348
Mailboxes ................................................................................................................................ 349
Tunnels.............................................................................................................................................. 351
General Considerations............................................................................................................ 351
Types of Tunnels ..................................................................................................................... 352
General Design Considerations................................................................................................ 352
Tunnel Sections ....................................................................................................................... 353
Examples of Tunnels ............................................................................................................... 355
Pedestrian Facilities........................................................................................................................... 357
Sidewalks................................................................................................................................. 357
Grade-Separated Pedestrian Crossings .................................................................................... 359Sidewalk Curb Ramps ............................................................................................................. 361
Bicycle Facilities............................................................................................................................... 367
Bus Turnouts ..................................................................................................................................... 367
Freeways.................................................................................................................................. 368
Arterials ................................................................................................................................... 368
Park-and-Ride Facilities .......................................................................................................... 370
Location.......................................................................................................................... 370
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Design Speed..................................................................................................................420
Sight Distance.................................................................................................................421
Grades.............................................................................................................................421
Alignment.......................................................................................................................421
Cross Slope.....................................................................................................................421
Superelevation................................................................................................................424Number of Lanes ............................................................................................................424
Width of Roadway..........................................................................................................424
Foreslopes.......................................................................................................................424
Structures........................................................................................................................426
Bridges to Remain in Place ............................................................................................426
Vertical Clearance ..........................................................................................................427
Horizontal Clearance to Obstructions.............................................................................427
Right-of-Way Width.......................................................................................................428
Intersection Design.........................................................................................................428
Railroad-Highway Grade Crossings...............................................................................428
Traffic Control Devices.................................................................................................. 429Erosion Control ..............................................................................................................429
Urban Collectors................................................................................................................................429
General Design Considerations................................................................................................429
Design Traffic Volumes .................................................................................................430
Design Speed..................................................................................................................430
Sight Distance.................................................................................................................431
Grades.............................................................................................................................431
Alignment.......................................................................................................................431
Cross Slope.....................................................................................................................431
Superelevation................................................................................................................431
Number of Lanes ............................................................................................................433Width of Roadway..........................................................................................................433
Parking Lanes .................................................................................................................433
Medians ..........................................................................................................................434
Curbs .............................................................................................................................. 435
Drainage .........................................................................................................................435
Sidewalks........................................................................................................................ 436
Driveways.......................................................................................................................436
Roadway Widths for Bridges..........................................................................................436
Vertical Clearance ..........................................................................................................436
Horizontal Clearance to Obstructions.............................................................................437
Right-of-Way Width.......................................................................................................437Provision for Utilities .....................................................................................................437
Border Area ....................................................................................................................438
Intersection Design.........................................................................................................438
Railroad-Highway Grade Crossings...............................................................................439
Street and Roadway Lighting .........................................................................................439
Traffic Control Devices.................................................................................................. 439
Erosion Control ..............................................................................................................440
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Landscaping ................................................................................................................... 440
References......................................................................................................................................... 440
Chapter 7
Rural and Urban Arterials
Introduction....................................................................................................................................... 443Rural Arterials................................................................................................................................... 443
General Characteristics............................................................................................................ 443
General Design Considerations................................................................................................ 444
Design Speed.................................................................................................................. 444
Design Traffic Volume................................................................................................... 444
Levels of Service............................................................................................................ 444
Sight Distance ................................................................................................................ 445
Alignment....................................................................................................................... 445
Grades ............................................................................................................................ 446
Number of Lanes............................................................................................................ 446
Superelevation................................................................................................................ 446
Cross Slope..................................................................................................................... 446
Vertical Clearances ........................................................................................................ 447
Structures........................................................................................................................ 447
Traffic Control Devices.................................................................................................. 447
Erosion Control .............................................................................................................. 447
Widths ............................................................................................................................ 448
Horizontal Clearance to Obstructions ............................................................................ 448
Cross Section and Right-of-Way.................................................................................... 449
Provision for Passing...................................................................................................... 449
Ultimate Development of Four-Lane Divided Arterials................................................. 450
Multilane Undivided Arterials ................................................................................................. 453
Divided Arterials ..................................................................................................................... 454
General Features............................................................................................................. 454
Lane Widths ................................................................................................................... 455
Cross Slope..................................................................................................................... 455
Shoulders........................................................................................................................ 455
Median Barrier Clearance .............................................................................................. 456
Medians.......................................................................................................................... 456
Alignment and Profile .................................................................................................... 457
Climbing Lanes on Multilane Arterials .......................................................................... 458
Superelevated Cross Sections......................................................................................... 459
Cross Section and Right-of-Way Widths ....................................................................... 462
Sections with Widely Separated Roadways ................................................................... 465
Intersections ................................................................................................................... 466
Access Management....................................................................................................... 467
Bikeways and Pedestrian Facilities ................................................................................ 467
Bus Turnouts .................................................................................................................. 468
Railroad-Highway Crossings ......................................................................................... 468
Rest Areas ...................................................................................................................... 468
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Urban Arterials ..................................................................................................................................469
General Characteristics ............................................................................................................469
General Design Considerations................................................................................................470
Design Speed..................................................................................................................470
Design Traffic Volume...................................................................................................470
Levels of Service ............................................................................................................ 470Sight Distance.................................................................................................................471
Alignment.......................................................................................................................471
Grades.............................................................................................................................471
Superelevation................................................................................................................471
Cross Slope.....................................................................................................................472
Vertical Clearances.........................................................................................................472
Lane Widths....................................................................................................................472
Curbs and Shoulders....................................................................................................... 473
Number of Lanes ............................................................................................................473
Width of Roadway..........................................................................................................474
Medians ..........................................................................................................................474Drainage .........................................................................................................................478
Parking Lanes .................................................................................................................478
Borders and Sidewalks ...................................................................................................479
Railroad-Highway Crossings..........................................................................................480
Roadway Width for Bridges...........................................................................................481
Bridges to Remain in Place ............................................................................................481
Horizontal Clearance to Obstructions.............................................................................481
Right-of-Way Width.......................................................................................................482
Traffic Barriers ............................................................................................................... 482
Access Management ................................................................................................................ 482
General Features.............................................................................................................482Access Control by Statute...............................................................................................483
Access Control by Zoning ..............................................................................................483
Access Control Through Driveway Regulations ............................................................483
Access Control through Geometric Design ....................................................................484
Pedestrian Facilities ................................................................................................................. 484
Provision for Utilities...............................................................................................................486
Intersection Design ..................................................................................................................486
Operational Control and Regulations.......................................................................................486
Traffic Control Devices.................................................................................................. 486
Regulatory Measures ......................................................................................................488
Operational and Control Measures for Right-Turn Maneuvers ......................................488Operational and Control Measures for Left-Turn Maneuvers ........................................488
Regulation of Curb Parking............................................................................................491
Directional Lane Usage .................................................................................................. 491
Frontage Roads and Outer Separations ....................................................................................494
Grade Separations and Interchanges ........................................................................................494
Erosion Control........................................................................................................................496
Lighting....................................................................................................................................496
2004 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
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Bikeways ................................................................................................................................. 496
Public Transit Facilities ........................................................................................................... 496
Location of Bus Stops .................................................................................................... 497
Bus Turnouts .................................................................................................................. 500
Reserved Bus Lanes ....................................................................................................... 500
Traffic Control Measures ............................................................................................... 501References......................................................................................................................................... 502
Chapter 8
Freeways
Introduction....................................................................................................................................... 503
General Design Considerations......................................................................................................... 503
Design Speed ........................................................................................................................... 503
Design Traffic Volumes........................................................................................................... 504
Levels of Service ..................................................................................................................... 504
Pavement and Shoulders.......................................................................................................... 504
Curbs........................................................................................................................................ 505
Superelevation ......................................................................................................................... 505
Grades...................................................................................................................................... 505
Structures................................................................................................................................. 506
Vertical Clearance.................................................................................................................... 506
Horizontal Clearance to Obstructions...................................................................................... 507
Ramps and Terminals .............................................................................................................. 508
Outer Separations, Borders, and Frontage Roads .................................................................... 508
Rural Freeways.................................................................................................................................. 508
Alignment and Profile.............................................................................................................. 509
Medians ................................................................................................................................... 509
Sideslopes ................................................................................................................................ 512
Frontage Roads ........................................................................................................................ 512
Urban Freeways................................................................................................................................. 513
General Design Characteristics................................................................................................ 513
Medians ................................................................................................................................... 513
Depressed Freeways ................................................................................................................ 513
General Characteristics .................................................................................................. 513
Slopes and Walls ............................................................................................................ 514
Typical Cross Section..................................................................................................... 515
Restricted Cross Section................................................................................................. 517
Walled Cross Section ..................................................................................................... 517
Examples of Depressed Freeways.................................................................................. 518
Elevated Freeways................................................................................................................... 520
General Characteristics .................................................................................................. 520
Medians.......................................................................................................................... 521
Ramps and Terminals..................................................................................................... 521
Frontage Roads............................................................................................................... 522
Clearance to Building Line............................................................................................. 522
Typical Cross Section..................................................................................................... 522
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Viaduct Freeways without Ramps.................................................................................. 523
Two-Way Viaduct Freeways with Ramps......................................................................524
Freeways on Earth Embankment....................................................................................525
Examples of Elevated Freeways.....................................................................................526
Ground-Level Freeways...........................................................................................................527
General Characteristics...................................................................................................527Typical Cross Section.....................................................................................................528
Restricted Cross Section.................................................................................................529
Example of a Ground-Level Freeway............................................................................. 530
Combination-Type Freeways...................................................................................................530
General Characteristics...................................................................................................530
Profile Control................................................................................................................ 531
Cross-Section Control.....................................................................................................533
Examples of Combination-Type Freeways.....................................................................533
Special Freeway Designs .........................................................................................................537
Reverse-Flow Roadways ................................................................................................537
Dual-Divided Freeways..................................................................................................540Freeways with Collector-Distributor Roads ...................................................................543
Accommodation of Transit and High-Occupancy Vehicle Facilities.......................................543
General Considerations...................................................................................................543
Buses .............................................................................................................................. 545
Rail Transit .....................................................................................................................550
References .........................................................................................................................................554
Chapter 9
Intersections
Introduction .......................................................................................................................................555
General Design Considerations and Objectives................................................................................. 555
Types and Examples of Intersections ................................................................................................558
General Considerations............................................................................................................558
Three-Leg Intersections ...........................................................................................................559
Basic Types of Intersections...........................................................................................559
Channelized Three-Leg Intersections.............................................................................564
Four-Leg Intersections ............................................................................................................. 565
Basic Types ....................................................................................................................565
Channelized Four-Leg Intersections...............................................................................566
Multileg Intersections ..............................................................................................................571
Modern Roundabouts...............................................................................................................574
Capacity Analysis.............................................................................................................................. 579
Alignment and Profile .......................................................................................................................579
General Considerations............................................................................................................579
Alignment ................................................................................................................................580
Profile.......................................................................................................................................582
Types of Turning Roadways.............................................................................................................. 583
General.....................................................................................................................................583
Minimum Edge-of-Traveled-Way Designs..................................................................