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Highway Design Handbook for Older Drivers and Pedestrians

FOREWORD

The proportion of the population over age 65 is growing significantly. Older road users can be expected to have problems driving and as pedestrians, given the known changes in their perceptual, cognitive, and psychomotor performances, presenting many challenges to transportation engineers, who must ensure system safety while increasing operational efficiency.

This Highway Design Handbook for Older Drivers and Pedestrians provides practitioners with a practical information source that links older road user characteristics to highway design, operational, and traffic engineering recommendations by addressing specific roadway features. This Handbook supplements existing standards and guidelines in the areas of highway geometry, operations, and traffic control devices.

The information in this Handbook should be of interest to highway designers, traffic engineers, and highway safety specialists involved in the design and operation of highway facilities. In addition, this Handbook will be of interest to researchers concerned with issues of older road user safety and mobility.

Copies of this report can be obtained through the FHWA Research and Technology Report Center, 9701 Philadelphia Court, Unit Q, Lanham, Maryland 20706, telephone: (301) 577-0906, fax: (301) 577-1421, or the National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia, 22161, telephone: (703) 487-4650, fax: (703) 321-8547.

Michael F. Trentacoste
Director, Office of Safety
Research and Development

TECHNICAL REPORT DOCUMENTATION PAGE

SI* (Modern Metric) Conversion Factors

ACKNOWLEDGMENTS

The quality and usefulness of the Highway Design Handbook for Older Drivers and Pedestrians is a direct result of the many highway engineering practitioners and researchers who provided their comments and criticisms to the authors of this document. Beginning with responses to a detailed, two-part survey conducted early in Handbook development, 94 practitioners contacted through 5 national committees identified the most important content for this resource and how it should be organized and presented for maximum accessibility by its intended users. Participating committees in this user requirements analysis included the American Association of State and Highway Transportation Officials (AASHTO) Subcommittee on Design; the National Committee on Uniform Traffic Control Devices (NCUTCD); the AASHTO Standing Committee on Highway Traffic Safety; the Transportation Research Board (TRB) Committee on Geometric Design (A2A02); and the TRB Committee on the Operational Effects of Geometrics (A3A08).

Following development of a draft document, a review panel composed of practicing engineers was asked to apply draft recommendations for one or more design elements from the Handbook in case studies involving real-world engineering problems, and to identify needed changes in the information presented in the Handbook. This panel was formed through the active support of three key committee chairmen: Mr. Thomas Warne, AASHTO Subcommittee on Design; Mr. Richard Weaver, AASHTO Subcommittee on Traffic Engineering; and Mr. Ken Kobetsky, National Committee on Uniform Traffic Control Devices. The 28 State and local engineers who served on this panel, giving freely of their time and talents, made invaluable contributions to the resulting product--the Older Driver Highway Design Handbook published by FHWA in 1998. They are acknowledged individually in that document.

Concurrent with the update of the 1998 Handbook, a series of practitioner workshops were held throughout the U.S. to increase awareness of this resource and to help educate engineers about the functional limitations of older drivers and pedestrians, and how to accommodate them through design and operational enhancements. These workshops, which provided contact with over 500 State DOT staff in a 3-year period, elicited verbal and written feedback from participants regarding Handbook deficiencies and needed improvements. While it is not feasible to name these participants, it is important to acknowledge their comments as the most powerful influence both in shaping changes to specific recommendations and in defining the need for, and manner of, cross referencing current Handbook recommendations against standard design manuals.

By integrating the feedback from workshop participants with the synthesis of recent research, a draft version of the new Handbook was developed. Additional reviews of this draft followed, in 2000, involving a diverse group of FHWA and State-level experts. Headquarters staff as well as staff in FHWA Division offices examined the present recommendations from the standpoint of their merit and also their compatibility with the MUTCD 2000; the State-level experts added a critical perspective on the feasibility and best strategies for implementation of Handbook recommendations.

The FHWA staff most important to the success of the Highway Design Handbook for Older Drivers and Pedestrians -- following Joseph Moyer, HRDS-07 and Elizabeth Alicandri, HSA-20, who both served as COTR -- include David Smith, HSA-30; Tim Penney, HEPH-1; Rudy Umbs, HSA-1; Joe Bared, HRDS-05; Carol Tan Esse, HRDS-05; George Schoene, HOTO-1; Linda Brown, HOTO-1; Bob Schlicht, HIPA-20; Bob Winans, HSA-10; Fred Small, HSA-10; Jeff Lewis, HDA-CA; Cathy Satterfield, HRC-MW-HS; David Morena, HTS-MI; Eric Worrell, Southern Resource Center; Emmett McDevitt, HTS-NY; Keith Harrison, HMH-WE; Ken Kochevar, HDA-CA; Ann Hersey, HA-MD; Roland Stanger, HPM-SD.2.2; David Snyder, OPS-NC; Greg Novak, HFO-NV; Rebecca Hiatt, IA Division; Bert McCauley, HFO-NV; Brad Hibbs, HRT-NC, and Jeff Holm, HDA-CA.

State-level experts making key contributions to the updated Handbook are listed below.

The authors are indebted to Dr. Susan Chrysler, 3M Traffic Control Materials Division; Michael R. King, Architect/Planner; Ms. Miriam Kloeppel, National Transportation Safety Board; and Ms. Esther Wagner, National Highway Traffic Safety Administration for their thoughtful review comments. Lawrence E. Decina of TransAnalytics and Gary Golembiewski of the Scientex Corporation were key to the production of this document. Finally, we wish to acknowledge the guidance and assistance of our Steering Group members Dr. Martin Pietrucha; Mr. Robert Walters; Mr. Ken Kobetsky; Ms. Lisa Fontana; Dr. Stephen H. Richards; and in particular, Dr. Daniel Fambro.

Loren Staplin, Kathy H. Lococo, Stanley R. Byington, David L. Harkey

May 2001

PREFACE

The increasing numbers and percentages of older drivers using the Nation's highways in the decades ahead will pose many challenges to transportation engineers, who must ensure system safety while increasing operational efficiency. The 65 and older age group, which numbered 33.5 million in the United States in 1995, will grow to more than 36 million by 2005 and will exceed 50 million by 2020, accounting for roughly one-fifth of the population of driving age in this country. In effect, if design is controlled by even 85th percentile performance requirements, the "design driver" of the early 21st century will be an individual over the age of 65.

There are important consequences of the changing demographics in our driving population. Traffic volumes will increase, problems with congestion will become more widespread, and the demands on drivers will grow significantly beyond present-day operating conditions. At the same time, maintenance of one's health and personal dignity, and in fact the overall quality of life for older persons, depends to an extraordinary degree on remaining independent. Independence requires mobility, and in our society the overwhelming choice of mobility options is the personal automobile. This means that there will be a steadily increasing proportion of drivers who experience declining vision; slowed decision-making and reaction times; exaggerated difficulty when dividing attention between traffic conflicts and other important sources of motorist information; and reductions in strength, flexibility, and general fitness.

In 1998, the FHWA published the Older Driver Highway Design Handbook, seeking to provide highway designers and engineers with a practical information source linking the declining functional capabilities of these highway users to design, operational, and traffic engineering enhancements keyed to specific roadway features. Experience with the included recommendations, including extensive feedback from local and State level practitioners, indicated a need to revise and update this resource. The result is the Highway Design Handbook for Older Drivers and Pedestrians. Recent research has been incorporated, format and content changes have been made to improve its usefulness, guidance on how to implement its recommendations has been added, and the range of applications covered by the Handbook has expanded relative to the 1998 document.

The main body of the Handbook is organized according to five broad site types, each containing one of more specific roadway features with associated design elements. The top priority is at-grade intersections, reflecting older drivers' most serious crash problem area. Next, older driver difficulties with merging/weaving and lane changing operations focus attention on inter-changes (grade separation). Roadway curvature and passing zones plus highway construction/work zones are included for two reasons: (1) heightened tracking (steering) demands may increase the driver's workload, and (2) there is an increased potential for unexpected events requiring a swift driver response. Finally, highway-rail grade crossings are identified as sites where conflicts are rare, and thus unexpected; and where problems of detection (with passive controls) are exaggerated due to sensory losses with advancing age.

Recommendations for all design elements covered in the Handbook are presented initially, followed by a more lengthy section presenting the Rationale and Supporting Evidence for each recommendation. Within each of these two major Handbook sections, material is organized in terms of five subsections, corresponding to the broad site types noted above. Preceding the recommendations, a section titled "How To Use This Handbook" explains codes used throughout the document to cross-reference the MUTCD, Green Book and other standard manuals, and suggests a structured approach to reaching decisions about when to implement Handbook recommendations. The Handbook concludes with an integrated glossary providing definitions of selected terms; a reference list; and an index to help locate Handbook entries pertaining to a particular design element.

The recommendations in this Handbook are based on supporting evidence drawn from a comprehensive review of research addressing human factors and highway safety. The results of field studies employing older drivers were always given precedence, followed by laboratory simulations or modeling efforts where both age and some aspect of highway design, operations, or traffic control were included as study variables. More general findings on the effects of aging, independent of driver performance research per se, may also be cited, but only where there is a clear logic extending a given finding to the highway context. A broader discussion of issues related to aging and driving can be found in the Transportation Research Board's Special Report 218 (1988) and in a pending TRB publication, A Decade of Experience, that updates the 1988 volume.

It is essential to recognize that the Handbook recommendations, as well as the evidence cited to support them, relate to demonstrated performance deficits of normally aging drivers and pedestrians. Thus, diminished driver capabilities that result from the onset of Alzheimer's disease and related dementias, which are believed to afflict over 10 percent of those age 65 and older and nearly 50 percent of those age 85 and older, are not the current focus.

To close, it should be emphasized that the recommendations presented in this Handbook do not constitute a new standard of required practice for the included highway design elements. The final decisions about when and where to apply each Handbook recommendation remain at the discretion of the practitioner. Hopefully, this resource can be applied preemptively to enhance safety wherever there are large numbers of older drivers in the traffic stream in a given jurisdiction; or, some may employ it primarily as a "problem solver" at older driver crash sites. As a practical matter, it is recognized that the application of Handbook recommendations may be limited to the design of new facilities and to planned highway reconstruction projects. Furthermore, the recommendations contained herein seek to avoid "optimum" solutions that may be unattainable using current materials or practices or that will result in situations where extreme costs are incurred for small anticipated gains in system safety. Ultimately, the contents of this Handbook are intended to provide guidance which--based on the current state-of-the-knowledge of the special needs of normally aging seniors--can be expected to significantly enhance the safety and ease of use of the highway system for older drivers in particular, and for the driving population as a whole.

TABLE OF CONTENTS

HOW TO USE THIS HANDBOOK

• RELATING RECOMMENDATIONS TO STANDARD DESIGN GUIDES
• INTERPRETING HANDBOOK GRAPHICS
• USING THE TIME-SPEED-DISTANCE TABLE
• KNOWING WHEN TO IMPLEMENT THESE RECOMMENDATIONS

RECOMMENDATIONS

• I. INTERSECTIONS (AT-GRADE)
  • Background and Scope of Handbook Recommendations
  • Recommendations by Design Element
    • A. Intersecting Angle (Skew)
    • B. Receiving Lane (Throat) Width for Turning Operations
    • C. Channelization
    • D. Intersection Sight-Distance Requirements
    • E. Offset (Single) Left-Turn Lane Geometry, Signing, and Delineation
    • F. Treatments/Delineation of Edgelines, Curbs, Medians, and Obstacles
    • G. Curb Radius
    • H. Traffic Control for Left-Turn Movements at Signalized Intersections
    • I. Traffic Control for Right-Turn/RTOR Movements at Signalized Intersections
    • J. Street-Name Signing
    • K. One-Way/Wrong-Way Signing
    • L. Stop- and Yield-Controlled Intersection Signing
    • M. Devices for Lane Assignment on Intersection Approach
    • N. Traffic Signals
    • O. Fixed Lighting Installations
    • P. Pedestrian Crossing Design, Operations, and Control
    • Q. Roundabouts

• II. INTERCHANGES (GRADE SEPARATION)
  • Background and Scope of Handbook Recommendations
  • Recommendations by Design Element
    • A. Exit Signing and Exit Ramp Gore Delineation
    • B. Acceleration/Deceleration Lane Design Features
    • C. Fixed Lighting Installations
    • D. Traffic Control Devices for Restricted or Prohibited Movements on Freeways, Expressways, and Ramp

• III. ROADWAY CURVATURE AND PASSING ZONES
  • Background and Scope of Handbook Recommendations
  • Recommendations by Design Element
    • A. Pavement Markings and Delineation on Horizontal Curves
    • B. Pavement Width on Horizontal Curves
    • C. Crest Vertical Curve Length and Advance Signing for Sight-Restricted Locations
    • D. Passing Zone Length, Passing Sight Distance, and Passing/Overtaking Lanes on Two-Lane Highways

• IV. CONSTRUCTION/WORK ZONES
  • Background and Scope of Handbook Recommendations
  • Recommendations by Design Element
    • A. Lane Closure/Lane Transition Practices
    • B. Portable Changeable (Variable) Message Signing Practices
    • C. Channelization Practices (Path Guidance)
    • D. Delineation of Crossovers/Alternate Travel Paths
    • E. Temporary Pavement Markings

• V. HIGHWAY-RAIL GRADE CROSSINGS (PASSIVE)
  • Background and Scope of Handbook Recommendations
  • Recommendations by Design Element

RATIONALE AND SUPPORTING EVIDENCE

• I. INTERSECTIONS (AT-GRADE)
  • A. Intersecting Angle (Skew)
  • B. Receiving Lane (Throat) Width for Turning Operations
  • C. Channelization
  • D. Intersection Sight-Distance Requirements
  • E. Offset (Single) Left-Turn Lane Geometry, Signing, and Delineation
  • F. Treatments/Delineation of Edgelines, Curbs, Medians, and Obstacles
  • G. Curb Radius
  • H. Traffic Control for Left-Turn Movements at Signalized Intersections
  • I. Traffic Control for Right-Turn/RTOR Movements at Signalized Intersections
  • J. Street-Name Signing
  • K. One-Way/Wrong-Way Signing
  • L. Stop- and Yield-Controlled Intersection Signing
  • M. Devices for Lane Assignment on Intersection Approach
  • N. Traffic Signals
  • O. Fixed Lighting Installations
  • P. Pedestrian Crossing Design, Operations, and Control
  • Q. Roundabouts

• II. INTERCHANGES (GRADE SEPARATION)
  • A. Exit Signing and Exit Ramp Gore Delineation
  • B. Acceleration/Deceleration Lane Design Features
  • C. Fixed Lighting Installations
  • D. Traffic Control Devices for Restricted or Prohibited Movements on Freeways, Expressways, and Ramps

• III. ROADWAY CURVATURE AND PASSING ZONES
  • A. Pavement Markings and Delineation on Horizontal Curves
  • B. Pavement Width on Horizontal Curves
  • C. Crest Vertical Curve Length and Advance Signing for Sight-Restricted Locations
  • D. Passing Zone Length, Passing Sight Distance, and Passing/Overtaking Lanes on Two-Lane Highways

• IV. CONSTRUCTION/WORK ZONES
  • A. Lane Closure/Lane Transition Practices
  • B. Portable Changeable (Variable) Message Signing Practices
  • C. Channelization Practices (Path Guidance)
  • D. Delineation of Crossovers/Alternate Travel Paths
  • E. Temporary Pavement Markings

• V. HIGHWAY-RAIL GRADE CROSSINGS (PASSIVE)

GLOSSARY

REFERENCES

ABBREVIATIONS AND ACRONYMS

LIST OF FIGURES

LIST OF TABLES

ABBREVIATIONS AND ACRONYMS

FHWA-RD-01-103