ORD Corridor base line geometry

Are you needing your corridor to follow an existing surface?  By saying "no design vertical", we can assume you're dealing with a milling project and may need multiple lanes following existing at specific controlling locations.  Milling templates can be arranged to have a null template origin where lane points are constrained horizontally and contain a "project to surface" vertical constraint.  

Short answer is no. A corridor requires horizontal and vertical geometry for the basis of its development. If your template is constructed in a manner that does not need a profile, then to speed up processing I would suggest applying a constant elevation to the line via the vertical tools. This will be faster than using existing ground as the active profile.

Can you please describe what you are trying to accomplish without any vertical data?

I'm trying to understand what this would even look like, or what use it might be. What is the purpose of a design without design data?