i am unable to detach reference in open road

Hi,

You are trying to detach a Managed Civil model so you need to remove its Default model as well. The only way to detach this is to select both the Default and Default-3D models at the same time and detach. Theres no way to keep the 3d model detached by itself in this situation. If you reattach the 2d model only, it will come back during Civil model operations.