The CGA example below can help with calculating the average slope of a curved street or sidewalk shape.
CGA stands for Computer Generated Architecture, a scripting language specific to Esri CityEngine and used to generate 3D content. See the link to the 'Basics of Rule-based Modeling' in the Related Information section below.
approxCurvedSlope = asin (scope.sy / geometry.du(0,unitSpace) )
print ( approxCurvedSlope )
Please note that this is example code and may not be useful in all situations.