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NZTA Technical Drawing – Typical Grading Plan
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The New Zealand Transport Agency (NZTA) has prepared a drawing detailing the correct site grading around a typical guardrail installation.  This drawing covers all new installations and maintenance situations.

The 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:

  • A minimum slope of 1:10 is required for a minimum of 600mm behind the guardrail
  • The slope of 1:10 is extended to a minimum of 1500mm at the impact head
  • The desirable slope for the clear area is 1:6 or flatter
  • Clear area is a minimum of 22.0m x 6.0m

Note: All grades are vertical : horizontal.

To view technical drawing, click here.

Auckland Central Nth Island Lower Nth Island Sth Island