Hi Brian,
Thank you for you response. The wavy path will be a road that descends from the top of a hill. I’m building the topography right now, which you helped me with a few weeks ago. I’d like the road to sweep down and follow the valleys with the road appearing very roughly like the SS below.

As you can see I’ve used a taper deformer here for the visual; maybe that’s the way to do it? If so it would need to travel along the spline ahead of the wave, which I’ve tried however the deformer keeps flicking back and forth, ie facing forward and switching direction backwards. It might be a solution if I can stabilise it.
As an addendum, is it possible to convert a tracer into a ‘regular’ spline, ie one that might be drawn? I’m think ahead a little as I’ll need a way of guiding the road through the topography.
I hope that helps; any further info will gladly be provided.
Cheers
Stephen