Hi, I am curious to know how to get the hair ‘Guide Simulate’ Node to make the guides collide with each other. I have Self Collisions turned on which allows a guide to collide with itself, but the guides still intersect other guides. I tried setting my Collision Handling to Local Geometric and Global Geometric with Repulsion but still no Collisions or Repulsion force being seen, they keep intersecting other hairs.

I opened up an old scene file from the forums to do with wire objects, and the two wires in the scene collide with itself and each other. It has an attribute called ‘collision width’ which doesn't appear to on the guide simulate node even though it seems the Guides in the Guide Simulate Node are Wires.

Any clues how to get hair colliding with other hair?

Well I think the wire width is the key. Just visualize the width and make sure it is appropriate to the size of the wire objects you are using, and also that self-collisions are enabled, which is sounds like you did. Any further advice would require a scene file unfortunately.