2002 aashto roadside design guide a concise overview
TRANSCRIPT
2002 AASHTO 2002 AASHTO ROADSIDE DESIGN GUIDEROADSIDE DESIGN GUIDE
A CONCISE OVERVIEW
It combined and updated information from: The 1974 AASHTO “Yellow Book,” Highway Design and
Operational Practices Related to Highway Safety The 1977 AASHTO “Barrier Guide,” Guide for Selecting,
Locating, and Designing Traffic Barriers Numerous research reports on various aspects of
roadside safety
The first edition of the AASHTO Roadside Design Guide was published in 1989.
BackgroundBackground
Introduction Roadside Safety and
Economics Roadside Topography and
Drainage Features Sign and Luminaire
Supports and Similar Roadside Features
Roadside Barriers (including terminals)
Median Barriers (including terminals)
Bridge Railings Crash Cushions Safety Appurtenances for
Work Zones
The first Roadside Design Guide contained nine chapters:
BackgroundBackground
In addition, the 1996 RDG : Moved barrier end treatments from the roadside and
median barrier chapters to Chapter 8, combining them with crash cushions.
Added Chapter 10, Roadside Safety in Urban and/or Restricted Environments.
The most obvious change in the second edition, 1996, was metrication.
BackgroundBackground
Additional changes include: For the most part, only hardware meeting NCHRP
Report 350 test evaluation criteria is included. Chapter 11, Erecting Mailboxes on Streets and
Highways, has been added, replacing the AASHTO guide publication of the same name.
The New GuideThe New Guide
The 2002 Edition of the Roadside Design Guide is written in dual units per AASHTO policy.
Roadside Safety Analysis Program (RSAP)
The New GuideThe New Guide
One additional change in the 2002 RDG is the substitution of a new cost-effectiveness algorithm for comparing alternative safety improvement designs. This new computer program, which replaces “ROADSIDE,” is called the “Roadside Safety Analysis Program,” or RSAP. While it will be described in Appendix A of the 2002 RDG, the computer program itself and a User’s Guide will be distributed separately.
The New GuideThe New Guide
Design Options for Safer Roadsides
Common to all editions of the Roadside Design Guide are the design options for creating safer roadsides. These design options, in order of preference, are:
• Remove the obstacle
• Redesign the obstacle so it can be safely traversed
• Relocate the obstacle
• Reduce the impact severity using a breakaway device
• Shield the obstacle using a traffic barrier or crash cushion
The New GuideThe New Guide
Design Options for Safer Roadsides (cont.)
These design options are discussed in more detail on the following slides, with significant changes since 1996 shown in yellow.
Note: Chapters 1 and 2 remain introductory chapters. Where appropriate, the figures and tables have been updated, but there are no significant changes in content.
Design Options:
Remove, Redesign, or Relocate
To the extent practical, all roadsides should be traversable and contain no objects likely to cause severe injuries when struck by a motorist. This concept is the cornerstone of the “forgiving roadside” philosophy.
Chapter 3, Roadside Topography and Drainage Features, addresses the clear zone issue and the safety treatment of ditches, pipes, and culverts in the roadside.
Chapter 3: Roadside Topography and Drainage Features
Recommended clear zones are minimums Minimum clear zone increases as foreslopes
become steeper Curbs have no physical effect on clear zone Transverse slopes must be much flatter than
parallel slopes Pipes should “match” traversable slopes
New in
2002
Culvert Treatment on Embankment Foreslope
Culvert Treatment on Embankment Foreslope
Culvert Treatment on Transverse Slope
Culvert Treatment on Transverse Slope
Roadside hardware that cannot be removed or located farther from the roadway should be designed to yield when struck, decreasing the likelihood of serious injury.
Chapter 4 on supports, poles, and trees, and Chapter 11 on mailboxes identify acceptable breakaway designs and installation practices for sign supports and poles in the right-of-way.
Design Options:
Reduce Impact Severity
Chapter 4: Supports, Poles, Trees, and Similar Roadside Features
Use breakaway designs where feasible Move farther from roadway Shield with barrier or crash cushion Maintain existing recovery areas
Unshielded overhead sign support
Chapter 11: Mailboxes
New chapter Deadly designs Crashworthy designs New concerns
New in
2002
Neighborhood Collection and Delivery Boxes
Whenever a hazardous terrain feature or fixed object cannot be eliminated through redesign or made to yield on impact, shielding with an appropriate traffic barrier should be considered.
Chapters 5, 6, and 7 present design details for crashworthy roadside and median barriers and bridge railings, respectively.
Chapter 8 provides information on acceptable terminals (end treatments) for traffic barriers, and on crash cushions.
Design Options:
Shield the Obstacle
Chapters 5-7: Longitudinal Barriers and Bridge Railings
Use crashworthy barriers Select appropriate test level Install barrier properly Reduced emphasis on specific bridge
railing designs
New in
2002
New in
2002
Chapter 8: Barrier Terminals and Crash Cushions
Barriers terminals Selection and site grading Crash Cushions
New in
2002
Chapter 9, Traffic Barriers, Traffic Control Devices, and Other safety Features for Work Zones, presents information on the selection, location, and design of hardware typically used in work zones, including temporary barriers.
Chapter 10, Roadside Safety in Urban or Restricted Environments, provides general guidance on the application of safe roadside concepts where the designer’s options may be limited by geometric, aesthetic, or environmental concerns.
Design Options:
Applications in Work Zones and Urban Areas
Chapter 9: Work Zone Devices
Additional information on Category I & II work zone devices (cones, drums, signs, barricades)
Expanded discussion on Category III devices (temporary barriers and truck-mounted attenuators)
New in
2002
Chapter 10: Urban Roadside Design Concerns
Addresses application of roadside design principles where limited rights-of-way restrict available options
Re-emphasizes clear zone considerations in urban areas
Incorporates former AASHTO Guide for Protective Screening of Overpass Structures
New in
2002
Treatment to Preserve Existing Bridge Railing
Inappropriate Landscaping ?
To learn more…
Order the 2002 Roadside Design Guide directly from AASHTO’s Online Bookstore at www.transportation.org
Request the National Highway Institute (NHI) 2-day training course on the 2002 AASHTO Roadside Design Guide
Coming soon: Individual training available via the Internet through the NHI’s 6-hour web-based training course
2002 Roadside Design Guide2002 Roadside Design Guide