Draw Clear Zone tool in Plan/3D that reads from AASHTOW roadside design tables for offsets and slopes from the model.
AASHTO Roadside Design Guide - 4th Edition, 2011, with July 2015 Errata Incorporated
Chapter 3.1
This would take inputs from the model (design speed, proposed inslopes, tangent or curve radius) look up the clear zone from tables and draw accordingly. It would not always be parallel if the inslopes change or on the outside of a horizontal curve.
Could you elaborate why using the offset parallel tool doesn't fit your needs?
AASHTO Roadside Design Guide - 4th Edition, 2011, with July 2015 Errata Incorporated
Chapter 3.1
This would take inputs from the model (design speed, proposed inslopes, tangent or curve radius) look up the clear zone from tables and draw accordingly. It would not always be parallel if the inslopes change or on the outside of a horizontal curve.
Could you elaborate why using the offset parallel tool doesn't fit your needs?