This rule create an rail guideway, with retaining walls on both sides. If elevated off the ground it will automatically create pillars to support itself down to the elevation surface. You can control the thickness and frequency of the pillars with rule parameters. Height is control by manipulating the height of each graph segment. Note, this rule is meant to be used exclusively in CityEngine, not ArcGIS Pro.
You can see a video of it in action here: https://youtu.be/sC4pWxbbK84
Give CityEngine a try with this free 30-day trial: http://bit.ly/EsriCETrialLink