Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: AASHTO RSDGCHP6:2006
• Năm ban hành / Publication date: 2006
• Tình trạng / Status: A - Còn hiệu lực
• Tên tiếng Anh / Title in English: Roadside Design Guide Chapter Six Update
• Số trang / Page: 50

Phạm vi áp dụng / Scope of standard

PREFACE

The Roadside Design Guide is developed and maintained
by the AASHTO Subcommittee on Design, Technical Committee for
Roadside Safety. The guide presents a synthesis of current
information and operating practices related to roadside safety and
is written in dual units-metric and U.S. Customary units. The 2006
edition of the guide supersedes the 1996 AASHTO publication of the
same name and includes an update to Chapter 6, "Median Barriers,"
which replaces Chapter 6 of the 2002 edition.

In this guide, the roadside is defined as that area beyond the
traveled way (driving lanes) and the shoulder (if any) of the
roadway itself. Consequently, roadside delineation, shoulder
surface treatments, and similar onroadway safety features are not
extensively discussed. While it is a readily accepted fact that
safety can best be served by keeping motorists on the road, the
focus of the guide is on safety treatments that minimize the
likelihood of serious injuries when a driver runs off the road.

A second noteworthy point is that this document is a guide. It
is not a standard, nor is it a design policy. It is intended for
use as a resource document from which individual highway agencies
can develop standards and policies. While much of the material in
the guide can be considered universal in its application, there are
several recommendations that are subjective in nature and may need
modification to fit local conditions. However, it is important that
significant deviations from the guide be based on operational
experience and objective analysis.

To be consistent with AASHTO's A Policy on Geometric Design
of Highways and Streets, design speed is as the basic speed
parameter to be used in this guide. However, since the design speed
is often selected based on the most restrictive physical features
found on a specific project, there may be a significant percentage
of a project length where that speed will be exceeded by a
reasonable and prudent driver. Conversely, there will be other
instances where roadway conditions will prevent most motorists from
driving as fast as the design speed. Because roadside safety design
is intended to minimize the consequences of a motorist leaving the
roadway inadvertently, the designer should consider the speed at
which encroachments are most likely to occur when selecting an
appropriate roadside design standard or feature.

Design values are presented in this document in both metric and
U.S. Customary units. The relationship between the metric and US.
Customary values is neither an exact (soft) conversion nor a
completely rationalized (hard) conversion. The metric values are
those that would have been used had the guide been presented
exclusively in metric units; the U.S. Customary values are those
that would have been used if the guide had been presented
exclusively in U.S. Customary units. Therefore, the user is advised
to work entirely in one system and not to attempt to convert
directly between the two.

The reader is cautioned that roadside safety is a rapidly
changing field of study, and changes in policy, criteria, and
technology are certain to occur after this document is published.
Efforts should be made to incorporate the appropriate current
design elements into the project development. Comments from users
of this guide on suggested changes or modifications resulting from
further developmental work or hands-on experience are appreciated.
All such comments should be addressed to the American Association
of State Highway and Transportation Officials, Engineering Program,
444 North Capitol Street NW, Suite 249, Washington, DC 20001.