Road Box Out - How to?

Good afternoon.

Would anyone be able to assist with how to box out the proposed road pavements please?

I was given a natural & design TIN file and a PDF showing the face of kerbs of the roads.

I can trace the face of kerbs using the 'strip' function, but how do I offset this line 600mm to the outside of the road which represents the extent of the base and subbase layers below?

I will try and upload a section sketch.

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I cant seem to post a photo from my phone. I will keep trying.