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Publication Number: FHWA-RD-01-103
Date: May 2001

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

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high–quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

 

TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.

FHWA-RD-01-103

2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle

HIGHWAY DESIGN HANDBOOK FOR OLDER DRIVERS AND PEDESTRIANS

5. Report Date

May 2001

6. Performing Organization Code
1495
7. Author(s)
Staplin, L., Lococo, K., Byington, S., and Harkey, D.
8. Performing Organization Report No.
1495/FR
9. Performing Organization Name and Address

The Scientex Corporation
2000 14th Street, N. #300
Arlington, VA 22201

TransAnalytics, LLC
1722 Sumneytown Pike, Box 328
Kulpsville, PA 19443

10. Work Unit No. (TRAIS)
NCP. No. 3A6a-0042
11. Contract or Grant No.
DTFH61-97-C-00050
12. Sponsoring Agency Name and Address

Office of Safety and Traffic Operations R&D
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report
Sept. 1997 - May 2001

14. Sponsoring Agency Code
15. Supplementary Notes

COTR: Joseph Moyer, HRDS-07; Elizabeth Alicandri, HSA-20; Kelley Pecheux, HRDS-07/SAIC

16. Abstract

This project updated, revised, and expanded the scope of the Older Driver Highway Design Handbook published by FHWA in 1998. The resulting document incorporates new research findings and technical developments; extensive feedback from state, county, and municipal engineers who reviewed and applied recommendations from the earlier version of the Handbook; and recommendations with supporting background material for aspects of modern roundabouts and highway-rail grade crossings, two elements which were not covered in the 1998 publication. Recommendations geared to use of highway facilities by pedestrians also receive greater emphasis. Guidance on how and when to implement the included recommendations has been added, as well as codes which indicate at a glance the relationship of each recommendation with standard design manuals including the MUTCD and the AASHTO Green Book.

Development of the updated Handbook was complemented in this project by a technology transfer initiative to make practitioners aware of the Handbook and assist in applying its recommendations. This included the development of a condensed document,Guidelines and Recommendations to Accommodate Older Drivers and Pedestrians (FHWA-RD-01- 051); plus printed and electronic materials supporting the conduct of practitioner workshops throughout the U.S. in the 1999-2001 period.

All research products developed under this contract are designed to provide practical guidance to engineers to accommodate the needs and functional limitations of an aging population of road users. Included recommendations are directed toward new construction, reconstruction, scheduled maintenance, and 'spot treatments' to ameliorate demonstrated safety problems, emphasizing countermeasures with modest additional cost during installation and the potential for cost savings over the life cycle.

17. Key Words

Safety, Highway Design, Highway Operations, Driver Age, Driver Performance, Human Factors, Vision, Attention, Perception, Cognition, Memory, Physical Ability, Risk Perception, Hazard Perception.

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page)

Unclassified

21. No. of Pages

362

22. Price
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

 


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.

N. Alexander
New York State Department of Transportation
Sue Lodahl
Minnesota Department of Transportation
Peter Amakobe
Wisconsin Department of Transportation
Patrick McCoy
University of Nebraska-Lincoln
Rick Beck
Minnesota Department of Transportation
Gary Metzer
Wisconsin Department of Transportation
Jon Bray
New York State Department of Transportation
Marchon Miller
Nevada Regional Transportation Commission
Jim Bryden
New York State Department of Transportation
G.G. (Buddy) Murr
North Carolina Department of Transportation
Paul J. Carlson
Texas Transportation Institute
Barbara O'Rourke
New York State Department of Transportation
James M. Ercolano
New York State Department of Transportation
Charles Riedel
New York State Department of Transportation
Charles Guenzel
New Jersey Department of Transportation
Gary Ries
Minnesota Department of Transportation
Zubair Haider
Indiana Department of Transportation
Robert Swanson
Minnesota Department of Transportation
Carol A. Hennessy
New York State Department of Transportation
Linda Voss
Kansas Department of Transportation
Carla W. Holmes
Georgia Department of Transportation
Micheal Weiss
Minnesota Department of Transportation
Ron King
North Carolina Department of Transportation
Mitch Wiebe
Minnesota Department of Transportation

 

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

RECOMMENDATIONS

RATIONALE AND SUPPORTING EVIDENCE

GLOSSARY

REFERENCES

ABBREVIATIONS AND ACRONYMS

 


LIST OF FIGURES

Figure
   
1 Turning path taken by left-turning vehicles, where 1=encroach into opposing cross-traffic stream; 2, 3, and 4=proper turning from different points within the intersection; and 5=left turn from a position requiring a greater-than-90-degree turn to enter the cross street.
2 Intersection geometries examined in the Staplin et al. (1997) field study of right-turn channelization.
3 Sight distance for left and right turns for passenger car drivers at yield-controlled intersections. Source: Harwood et al. (1993).
4 Spatial relationships that determine available sight distance. Source: McCoy, Navarro, and Witt (1992).
5

Comparison of required intersection sight distance values calculated using modified AASHTO model (J=2.5 s) and Gap Acceptance model using varying values for G.

6 Relationship of left-turn lanes for negative and positive offset geometry.
7 Alternative left-turn treatments for rural and suburban divided highways. Source: Bonneson, McCoy, and Truby (1993).
8 Difference in sight-distance restriction for an unpositioned driver and a positioned driver at an aligned intersection with an opposing left-turning driver.
9

Left-turn lane offset design values necessary to achieve unrestricted sight distances,and minimum required sight distances calculated either using the modified AASHTO model (J=2.5 s) or the Gap Acceptance model with G=8.0 s.

10 Alternative curb radii evaluated in laboratory preference study conducted by Staplin et al. (1997).
11

Novel sign tested as a countermeasure by Zegeer and Cynecki, 1986.

12

Recommended signing configuration at divided highway crossings for medians less than or equal to 9 m (30 ft), based on evidence provided by Crowley and Seguin, 1986.

13 Recommended location of ONE WAY signs for T-type intersections. Source: Crowley and Seguin, 1986.
14

Recommended location of ONE WAY signs for intersection of a one-way and two-way street. Source: Crowley and Seguin, 1986.

15 One-Way and Chevron sign combination for use in central island of roundabout.
16 Signs used on approaches to Maryland roundabouts.
17 Signs used at Maryland roundabouts.
18 Example of signing used by Brackett, Huchingson, Trout, and Womack (1992) to compare (a) comprehension of MUTCD diagrammatics and (b) modified diagrammatics.
19 The entry process and components of the entry model developed in NCHRP 3-35.
20

The exit process and components of the exit model developed in NCHRP 3-35.

21 Pixel layout of LSC heads employed in research conducted by Ullman et al., 1996.
22 Enhanced Crossbuck sign, referred to as the "Buckeye Crossbuck" or "Conrail Shield."
23 Standard W10-3 sign and alternative sign designs evaluated by Picha, Hawkins, and Womak (1995).

 


LIST OF TABLES

Table
   
1 Cross-references of related entries for intersecting angle (skew).
2 Cross-references of related entries for receiving lane (throat) width for turning operations.
3 Cross-references of related entries for channelization.
4 Cross-references of related entries for intersection sight distance requirements.
5 Expected reduction in number of crashes per intersection per year. Source: David and Norman, 1979.
6 Comparison of clearance times obtained in the Staplin et al. (1997) field study with AASHTO Green Book values used in sight distance calculations.
7 Cross-references of related entries for offset (single) left-turn lane geometry, signing, and delineation.
8 Cross-references of related entries for treatments/delineation of edgelines, curbs, medians, and obstacles.
9

Contrast requirements for edgeline visibility at 122 m (400 ft) with 5-s preview at a speed of 88 km/h (55 mi/h), as determined by PC DETECT computer model.

10 Cross-references of related entries for curb radius.
11

Cross-references of related entries for left-turn movements at signalized intersections.

12 Cross-references of related entries for traffic control for right turn/RTOR movements at signalized intersections.
13 Cross-references of related entries for street-name signing.
14 Fonts tested by Garvey, Pietrucha, and Meeker (1997).
15

Daytime and Nighttime Recognition Distances for Fonts Studied by Garvey, Pietrucha, and Meeker (1997).

16

Daytime and Nighttime Legibility Distances for Fonts Studied by Garvey, Pietrucha, and Meeker (1997).

17

Cross-references of related entries for one-way/wrong-way signing.

18

Cross-references of related entries for stop- and yield-controlled intersection signing.

19

Minimum (maintained) retroreflectivity guidelines for white on red signs specified by Paniati and Mace (1993) to accommodate 75 to 85 percent of all drivers.

20 Cross-references of related entries for devices for lane assignment on intersection approach.
21

Cross-references of related entries for traffic signals.

22

Peak (minimum) daytime intensity requirement (cd) for maintained signals with no backplate. Source: Janoff, 1990.

23 Signal Head Designs Evaluated by Holowachuk et al. (1993, 1994).
24

Cross-references of related entries for fixed lighting installations.

25 Cross-references of related entries for pedestrian crossing design, operations, and control.
26 Cross-references of related entries for roundabouts.
27

Before and after average annual crash history for the five intersections in Maryland that were converted to roundabouts. Source: Niederhauser, Collins, and Myers, 1997.

28

Causes of crashes at urban roundabouts in France. Source: Ourston and Bared, 1995.

29 Design-speed recommendations by roadway class, for modern roundabouts.Source: Wallwork, 1999.
30 Cross-references of related entries for exit signing and exit ramp gore delineation.
31

Cross-references of related entries for acceleration/deceleration lane design features.

32

Cross-references of related entries for fixed lighting installations.

33

Relative annual effect of lighting type on total nighttime crashes (n=400) at urban and nonurban interchanges. Source: Gramza, Hall, and Sampson, 1980.

34 Cross-references of related entries for traffic control devices for restricted or prohibited movements on freeways, expressways, and ramps.
35

Median legibility distance (meters) of lane control signals, as a function of driver age, LCS type, and LCS symbol. Source: Ullman, Parma, Peoples, Trout, and Tallamraju, 1996.

36

Cross-references of related entries for pavement markings and delineation on horizontal curves.

37

Minimum required RL (mcd/m2/lux) recommended by Zwahlen and Schnell (1998) for roads consisting of two white edgelines and a dashed yellow or white centerline.

38 Cross-references of related entries for pavement width on horizontal curves.
39

Percent reduction in crashes on horizontal curves with 2.4 m (8 ft) beginning lane width as a result of lane widening, paved shoulder widening, and unpaved shoulder widening. Source: Zegeer et al., 1990.

40

Cross-references of related entries for crest vertical curve length and advance signing for sight-restricted locations.

41

Cross-references of related entries for passing zone length, passing sight distance, and passing/overtaking lanes on two-lane highways.

42 Cross-references of related entries for lane closure/lane transition practices.
43 Subject performance as a function of sheeting type (fluorescent orange Type VII vs. standard orange Type VII), as a function of subject age group and lighting condition. Source: Jenssen, Moen, Brekke, Augdal, and Sjøhaug, 1996.
44 Luminance contrast ratio ([Lt-Lb]/Lb) under different lighting conditions, for fluorescent orange and standard highway orange signs. Source: Burns and Pavelka, 1995.
45

Recommended minimum on- and off-axis lamp intensities of arrow panels to ensure daytime visibility by older drivers, and the maximum intensity recommended for nighttime operations to ensure safe levels of discomfort and disability glare for older drivers, for high-speed (73 km/h [45 mi/h]) and low-speed (<73 km/h [45 mi/h]) roadways. Source: Mace, Finkle, and Pennak, 1996.

46 Cross-references of related entries for portable changeable (variable) message signing practices.
47 Variables evaluated by Garvey and Mace (1996) using a CMS simulator to determine the optimum character legibility.
48

Legibility index obtained by Garvey and Mace (1996) in a laboratory study of CMS character legibility, as a function of driver age, sign color, and percent of drivers accommodated.

49 Day and night predicted legibility distances for various sign technologies. Source: Upchurch et al., 1991.
50 "Acceptable" abbreviations for frequently used words. Source: Dudek, Huchingson, Williams, and Koppa (1981).
51

Abbreviations that are "not acceptable." Source: Dudek, Huchingson, Williams, and Koppa (1981).

52 Abbreviations+ that are "acceptable with a prompt." Source: Dudek, Huchingson, Williams, and Koppa (1981).
53

Cross-references of related entries for channelization practices (path guidance).

54 Cross-references of related entries for delineation of crossovers/alternative travel paths.
55 Cross-references of related entries for temporary pavement markings.
56

Temporary pavement marking treatments evaluated by Dudek, Huchingson, and Woods (1986).

57

Cross-references of related entries for passive crossing control devices.

 


ABBREVIATIONS AND ACRONYMS

AAAFTS

American Automobile Association Foundation for Traffic Safety
AADT

annual average daily traffic

AASHTO

American Association of State and Highway Transportation Officials

ASTM

American Society for Testing and Materials

ATSSA

American Traffic Safety Services Association

cd

candela

CIE

Commission Internationale de l'Eclairage

CIL

complete interchange lighting

CMS

changeable message sign

CSSB

concrete safety-shaped barrier
DS diverge steering
DSD decision sight distance
FARS Fatal Accident Reporting System
FHWA Federal Highway Administration
fL

footlambert

GSA gap search and acceptance
hfc horizontal footcandle
IA initial acceleration
IIHS Insurance Institute for Highway Safety
ISD intersection sight distance
ISBL in-service brightness level
ISTEA

Intermodal Surface Transportation Efficiency Act

ITE

Institute of Transportation Engineers

LI legibility index
LPI leading pedestrian interval
MOE measure of effectiveness
MRVD minimum required visibility distance
MSC merge steering control
MUTCD

Manual on Uniform Traffic Control Devices for Streets and Highways

NCHRP National Cooperative Highway Research Program
NHTSA National Highway Traffic Safety Administration
NTOR no turn on red
NTSB National Transportation Safety Board
PIL partial interchange lighting
PMD post-mounted delineator
PRT perception-reaction time
RT reaction time
RPM raised pavement markers
RTOR right turn on red
SC steering control
SCL speed-change lane
SSD stopping sight distance
STV small target visibility
SU single unit (truck)
TCD traffic control device
TRB Transportation Research Board
TVA

transient visual adaptation

TWLTL

two-way, left-turn lane

VC visual clear

 

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