I was reading the Mirgorod post about their highway and how they were strugglying with fences that would serve a purpose and not decay, something that looks good for a border.
Hedge fences. These bushes could be decorated with flowers or tapestry, banners, flags, etc. to create a nice looking border for highways.
They would provide no true barrier, but instead, force people to a crawl who pass through. They wouldnt be a defensive structure and in the grand scheme of things, be relatively easy to destroy for any vandal.
Walking through them runs a small chance of creating a temporary debuff that affects perception called "ow! my eye"