Geometric Design of Junctions (priority junctions, direct ...

1 Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) DN-GEO-03060 June 2017 TRANSPORT INFRASTRUCTURE IRELAND (TII) PUBLICATIONS About TII Transport Infrastructure Ireland (TII) is responsible for managing and improving the country s national road and light rail networks. About TII Publications TII maintains an online suite of technical publications, which is managed through the TII Publications website. The contents of TII Publications is clearly split into Standards and Technical documentation. All documentation for implementation on TII schemes is collectively referred to as TII Publications (Standards), and all other documentation within the system is collectively referred to as TII Publications (Technical).

2 Document Attributes Each document within TII Publications has a range of attributes associated with it, which allows for efficient access and retrieval of the document from the website. These attributes are also contained on the inside cover of each current document, for reference. TII Publication Title Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) TII Publication Number DN-GEO-03060 Activity Design (DN) Document Set Standards Stream Geometry (GEO) Publication Date June 2017 Document Number 03060 Historical Reference N/A TII Publications Website This document is part of the TII publications system all of which is available free of charge at For more information on the TII Publications system or to access further TII Publications documentation, please refer to the TII Publications website.

3 TII Authorisation and Contact Details This document has been authorised by the Director of Professional Services, Transport Infrastructure Ireland. For any further guidance on the TII Publications system, please contact the following: Contact: Standards and Research Section, Transport Infrastructure Ireland Postal Address: Parkgate Business Centre, Parkgate Street, Dublin 8, D08 DK10 Telephone: +353 1 646 3600 Email: TRANSPORT INFRASTRUCTURE IRELAND (TII) PUBLICATIONS Page i TII Publications Activity: Design (DN) Stream: Geometry (GEO) TII Publication Title: Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) TII Publication Number: DN-GEO-03060 Publication Date: June 2017 Set: Standards Contents 1.

4 Introduction .. 1 2. Junction Types .. 7 3. road Safety .. 20 4. Selection of Junction Type .. 24 5. Geometric Design of Priority Junctions & Vehicular Access to National roads . 32 6. Geometric Design of Roundabouts .. 64 7. Layout of Grade Separated Junctions .. 106 8. Layout of Compact Grade Separated Junctions .. 153 9. References .. 166 .. 168 .. 171 .. 182 .. 184 TII Publications DN-GEO-03060 Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) June 2017 Page ii Updates to TII Publications resulting in changes to Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) DN-GEO-03060 Date: June 2017 Amendment Details: This Standard supersedes: a) DN-GEO-03043 (TD 41-42) Geometric Design of Priority Junctions and Vehicular Access to National roads.

5 B) DN-GEO-03033 (TD 16) Geometric Design of Roundabouts. c) DN-GEO-03035 (TD 22) Layout of Grade Separated Junctions . d) DN-GEO-03042 (TD 40) Layout of Compact Grade Separated Junctions . e) DN-GEO-03045 (TD 51) Segregated Left Turn Lanes and Subsidiary Deflection Islands at roundabouts . f) DN-GEO-03032 (TD 10) road Link Design for Type 2 and Type 3 Dual Carriageways. The details in relation to Junctions on Type 2 and Type 3 Dual Carriageways have been incorporated. This standard combines the requirements of the above superseded standards into one consolidated standard for the Geometric Design of Junctions . This version of the Standard supersedes the April 2017 Publication of DN-GEO-03060. The principal changes from the April 2017 version of this Standard are as follows: Chapter 1 Definitions a) The definition of a near straight that is required downstream and upstream of diverge and merge noses as per Section & has been corrected to specify the Desirable Minimum Radius for the mainline Design speed.

6 Chapter 2 Junction Types a) Figure updated with photograph showing channelising island in the minor road approach. b) Section d) updated to clarify that priority Junctions incorporating traffic signals shall generally not be provided on national roads in rural areas. c) Section a) has been updated to clarify that diamond Junctions are not permitted on national roads in rural areas, however diamond Junctions incorporating traffic signals at the connector road junction with the minor road are permitted in urban locations. Chapter 4 Selection of Junction Type a) Section has been revised to clarify that remedial measures at Junctions on existing roads are required to be submitted as part of the Preliminary Design Report in accordance with DN-GEO-03030.

7 Chapter 5 Geometric Design of Priority Junctions and Vehicular Access to National Roads a) Figure updated to reference Table : direct Taper Length. b) Table : y Visibility distances from the minor road has been updated to include parameters for lower Design speeds of 60km/h, 50km/h and 42km/h. TII Publications DN-GEO-03060 Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) June 2017 Page iii c) The minimum circular corner radii in Section for left in-left out priority Junctions on Type 2 Dual Carriageways and left in-left out Junctions forming part of a compact grade separated junction have been revised. d) Section has been updated to clarify that channelising islands at left in-left out Junctions shall be set back from the lane markings.

8 E) Figure has been updated to apply to priority left in-left out Junctions only with reference made to Chapter 8 for left in-left out priority Junctions forming part of a compact grade separated junction. f) Section wording and Figure updated to confirm ghost island turning lanes should normally be developed symmetrically about the centreline of the major road to and from the turning lane width at the tapers shown in Table g) Additional wording added to Section and new Figure added to clarify the required details where a right turn lane off the major road is provided at both Junctions within a right/left staggered junction. h) Section updated in relation to Merge and diverge auxiliary lanes and tapers on single carriageway roads.

9 I) Section updated to clarify the hard shoulder opposite a ghost island junction shall be tapered to form a hard strip over the length of the ghost island taper, figure updated accordingly. j) Section updated to provide clarity in relation to the provision of diverge auxiliary lanes on Type 2 Single Carriageway roads. Chapter 6 Geometric Design of Roundabouts a) Section has been updated to include a minimum distance between two roundabouts on a national road of 90m b) The requirements for the ICD of roundabouts contained in Section have been updated. c) A maximum entry path radius for roundabouts on rural national roads has been added to Section d) Section has been updated to allow for a relaxation of 50m on the provision of new priority Junctions or direct accesses on Regional and Local roads as per Section Chapter 7 Layout of Grade Separated Junctions a) Urban Motorway details included in Tables , and b) Weaving calculation details for Urban Motorways included in Section c) Table has been updated to relate the minimum radii for loops to the Design speed of the mainline.

10 D) Section in relation to transitioning between a hard shoulder and hard strip at merges and diverges has been updated, figures and have been updated accordingly. Chapter 8 Layout of Compact Grade Separated Junctions a) New figure added for left in-left out junction forming part of a compact grade separated junction has been included. b) Corner radii for left in-left out Junctions forming part of a compact grade separated junction have been updated and Design details for compact grade TII Publications DN-GEO-03060 Geometric Design of Junctions (priority Junctions , direct accesses, roundabouts, grade separated and compact grade separated Junctions ) June 2017 Page iv separated Junctions with diverge auxiliary lanes have been added to Section Date: September 2017 Amendment Details: The following minor amendments have been incorporated into the June 2017 version of this Standard.