Manual Notice: 2013-1

From: Mark A. Marek, P.E

Manual: Roadway Design Manual

Effective Date: December 11, 2013

Purpose

This revision is intended to update the Roadway Design Manual, specifically Chapter 2, Basic Design Criteria, based on 2011 American Association of State Highway and Transportation Officials (AASHTO) Geometric Design of Highways and Streets revisions.

Contents

The following changes have been made:

Chapter 1, Preface

  • Added non-discrimination statement.

Chapter 1, Section 2, Design Exceptions, Design Waivers and Design Variances

  • Subsection "New Location and Reconstruction Projects (4R )" - Added "Lateral offset to Obstructions" to list of controlling criteria that require a design exception.

Chapter 2, Basic Design Criteria

  • General renumbering of Tables and Figures throughout the chapter,
  • Updated English and Metric tables to current AASHTO values, and
  • Metric Versions are no longer shown but may be viewed in PDF format by accessing link.

Chapter 2, Section 3, Sight Distance

  • Subsection "Decision Sight Distance" - paragraph added at the end of subsection regarding a reduced decision zone,
  • Subsection "Passing Sight Distance" - added reference to Super 2 Highways for further discussion, and
  • Subsection "Intersection Sight Distance" - the second bullet describing the types of intersection controls has been rewritten.

Chapter 2, Section 4, Horizontal Alignment. This section has been completely reorganized for better flow and revisions are as follows:

  • Table 2-3, "Horizontal Curvature of High-Speed Highways and Connecting Roadways with Superelevation", updated to current AASHTO values.
  • Table 2-4, "Horizontal Curvature of Highways without Superelevation", updated to current AASHTO values. Values for 6% superelevation were added to table.
  • Table 2-5, "Minimum Radii and Superelevation for Low-Speed Urban Streets", updated to current AASHTO values.
  • Table 2-6, "Minimum Radii for Design Superelevation Rates, Design Speeds", and emax = 6%, updated to current AASHTO values.
  • Table 2-7, "Minimum Radii for Design Superelevation Rates", Design Speeds, and emax = 8%, updated to current AASHTO values.
  • Subsection "Superelevation Transition Length" - The first two paragraphs and Table 2-8 were relocated from the discussion on Superelevation in the current version of the manual. The last paragraph of this subsection and Table 2-9 "Multilane Adjustment Factor" were added.
  • Subsection "Superelevation Transition Placement" -This is a new section and provides updated guidance on placement of the transition, and Table 2-10, "Portion of Superelevation Transition Located on the Tangent", where were added from the current AASHTO "Green Book".
  • Subsection "Superelevation Transition Type" - This section is new and references the AASHTO "Green Book" for additional methods.
  • Subsection "Sight Distance on Horizontal Curves" - The last paragraph in the section was added regarding methods to mitigate barrier obstructions.

Chapter 2, Section 5, Vertical Alignment

  • Subsection "Crest Vertical Curves" - A sentence was added to the 3rd paragraph regarding successive vertical curves.
  • Subsection "Combination of Vertical and Horizontal Alignment" - The last bullet was modified to include reference to Super 2 Highways.

Chapter 2, Section 6, Cross Sectional Elements

  • The term "horizontal clearance" was replaced with "clear zone" throughout this section.
  • Updated this section to current Americans with Disabilities Act Public Accessibility Guideline for Pedestrian Facilities in the Public Right of Way (PROWAG) and Texas Accessibility Standards (TAS).
  • Subsection "Overview"
    • Added "Lateral Offset to Obstructions".
    • Changed "Horizontal Clearances to Obstructions" to "Clear Zone".
    • Moved "Slopes and Ditches" section down after "Roadside Design".
  • Subsection "Pavement Cross Slope" - The last paragraph was modified to delete reference to design exception.
  • Subsection "Lane Widths" - Added last paragraph discussing Bicycle Accommodations.
  • Subsection "Shoulder Widths" - Added 2nd paragraph regarding bicycle accommodations and offset to barriers.
  • Subsection "Sidewalks and Pedestrian Elements "- 1st paragraph was modified and factors when sidewalks should be included were added.
  • Subsection "Sidewalk Location" - The buffer space between back of curb and sidewalk was modified. Additional discussion was added at the end of paragraph.
  • Subsection "Sidewalk Width" - minor wording modifications to the two paragraphs.
  • Subsection "Street Crossing" - Dimensions for refuge islands and cut throughs were modified. Last line of paragraph was added.
  • Subsection "Curb Ramps and Landings" - modified 1st bullet to include reconstruction and rehabilitation. Added preferred width of curb ramps.
  • Subsection "Cross Slope" - added sentence to end of paragraph regarding the running slope of sidewalks across driveways.
  • Subsection "Street Furniture" - added a sentence to last paragraph discussing pedestrian push buttons.
  • Subsection "Slopes and Ditches" - relocated discussion. Deleted Table 2-10.
  • Subsection "Lateral Offset to Obstruction" - New section added.
  • Subsection "Clear Zone" - Changed section title from "Horizontal Clearances to Obstructions" to "Clear Zone" and discussion on definition.
  • Table 2-12 - The clear zone width changed from 1.5 ft to 4 ft minimum, and 3 ft to 6 ft desirable for "Urban, curbed, < 45 mph".

Chapter 2, Section 7, Drainage Facility Placement

  • The term "horizontal clearance" was replaced with "clear zone" throughout this section.
  • Subsection "Overview" - added "Side Ditches".
  • Subsection "Design Treatment of Cross Drainage Culvert Ends" - Bullets removed from first paragraph. Discussed in subsequent sections.
  • Subsection "Small Pipe Culverts" - combined paragraphs 3 and 4.
  • Subsection "Intermediate Size Single Box Culverts and (Single and Multiple) Pipe Culverts" - 2nd recommended safety treatment option not applicable to bridge class culverts.
  • Subsection "Multiple Box Culverts and Large single Pipes or Boxes": - 2nd recommended safety treatment option not applicable to bridge class culverts.
  • Subsection "Bridge Class Drainage Culverts" - added recommended treatment options to 2nd paragraph. Modified Table 2-14 and its title.
  • Figure 2-10, "Use of Guardrail at Bridge Class Culverts", depth of cover changed to ">9" to < 36".
  • Figure 2-11, "Use of Sloping Pipe Ends Without Cross Pipes", replaced the term Grates with Cross Pipes.
  • Figure 2-12, "Use of Sloping Pipe Ends with Cross Pipes", replaced the term Grates with Cross Pipes.
  • Subsection "Side Ditches" - added wording in the last paragraph regarding rock filter dam.

Instructions

This revision will be distributed online only.This manual, and all revisions, applies to all highway and street project development, whether developed by the department or with consultant staff. Due to projects that may be further along in development with current superelevation criteria, this manual, and all revisions, will be effective for all projects beginning with the December 2014 letting. Project development using this manual and its revisions prior to that date is at the option of the district.

Contact

For general comments and suggestions for future revisions of this manual, contact the Design Division, Roadway Design Section.

Copyright Notice

This Roadway Design Manual and all future revisions:Copyright ©2013 by Texas Department of TransportationPublished by the Design DivisionAll rights reserved.

Archives

Past manual notices are available in a pdf archive.

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