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Technical Note – W-Section to concrete transition detail
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The New Zealand Transport Agency (NZTA) has prepared a drawing detailing the correct layout and configuration of a W-section to concrete guardrail transition.  This drawing covers all new installations and maintenance situations.

The memo and drawing will soon be available from the NZTA website. If you have any enquiries regarding these details please contact the National Traffic & Safety Engineer, Highways & Network Operations, NZTA National Office or

The main points of this drawing are as follows:

  • The minimum transition length for W-section to concrete is 10.0m
  • All transition posts are steel with steel modified blockouts. No timber posts or blockouts are  to be used in the transition length
  • The transition is rated Test Level 4 (TL-4) and must be used transitioning from all semi-rigid  guardrail systems, both TL-3 or 4, proprietary and non-proprietary, to concrete
  • Where proper post embedment cannot be achieved then standard ‘I’ Beam bridge steel  posts on steel base plates and bolted to a concrete beam using necked bolts may be used

Note: The TL-3 Thrie-Beam on timber post transition has been withdrawn from NZ Transport Agency Specification M23 and is no longer compliant.
To view technical drawing, click here

Auckland, Northland and Central North Island Lower Nth Island Sth Island