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Geometric Design of

Highways and Streets2004

American Association of State Highwayand Transportation Officials

APOL

ICY

ON


2/46

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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iii

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.



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iv

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



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vi

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


Greer, Robert

Director, Office of Design

Florida Department of Transportation605 Suwannee Street, MS 38


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.


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



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vii

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.


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


P.O. Box 94759

Lincoln, NE 68509-4759

Turek, DonAssistant Design Engineer


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



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ix

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



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x

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



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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.



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xiv

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



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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


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



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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 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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xix

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


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 Design Procedures...................................................................................................... 345

Noise Reduction Designs......................................................................................................... 346

Roadside Control............................................................................................................................... 348

General Considerations............................................................................................................ 348Driveways................................................................................................................................ 348

Mailboxes ................................................................................................................................ 349

Tunnels.............................................................................................................................................. 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


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



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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


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


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


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



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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


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


Alignment ................................................................................................................................580

Profile.......................................................................................................................................582

Types of Turning Roadways.............................................................................................................. 583

General.....................................................................................................................................583

Minimum Edge-of-Traveled-Way Designs..................................................................

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