This is a critical point. Autodesk has moved to a subscription-only model. You cannot legally buy a new perpetual license for Civil 3D 2018 today. However, you can legally use the if:
Before we explore the specifics, let’s clarify the nomenclature. AutoCAD Civil 3D 2018 is the flagship software from Autodesk for Building Information Modeling (BIM) for civil infrastructure. The is a specific service pack and point release.
A new workflow for modeling and optimizing roadway rehabilitation, including specialized Rehab Subassemblies that handle complex cross-slope corrections.
Does Civil 3D 2018.1 Update include the Civil 3D 2018.0.1 Update?