Road design

Cover of Guide to Road Design Part 4A: Unsignalised and Signalised Intersections
Guide to Road Design Part 4A: Unsignalised and Signalised Intersections
  • Publication no: AGRD04A-17
  • ISBN: 978-1-925451-73-3
  • Published: 7 June 2017
  • Edition: 3

Guide to Road Design Part 4A: Unsignalised and Signalised Intersections provides road designers and other practitioners with guidance on the detailed geometric design of all at-grade intersections (excluding roundabouts).

This Part contains information for the design of signalised and unsignalised intersections. Guidance is provided on intersection sight distances, including approach sight distance, safe intersection sight distance, and minimum gap sight distance. Left and right turn treatments are outlined including the incorporation of auxiliary lanes at intersections and the use and size of traffic islands.

Edition 3.0 contains minor editorial and technical changes throughout the Guide, and substantial parts of Sections 1.4, 3.2, 4.3-4.14, 5.1, 5.2, 6.1, 7.1-7.5, 8, 9 and 10 have been transferred to Guide to Road Design Part 4: Intersections and Crossings – General.

Updates have been made throughout this edition to include new and updated reference material and cross‑references to other Guides. Most figures have been redrawn to provide a consistent appearance. The major updates include:

  • Section 1: Introduction: Updates to road safety, including the Safe System principles.
  • Section 3: Sight Distance: Incorporates additional information relating to safe intersection sight distance and additional description in tables to assist in interpretation.
  • Section 5: Auxiliary Lanes: Section 5.2 (new number), has information included from the commentaries on turning radii and vehicle speeds, and Table 5.4 contains additional information on acceleration lane lengths.
  • Section 6: Traffic Islands and Medians: Information from Appendix D has been included in Section 6.2.