If the junction definition is out-of-date, 
is displayed next to the junction in the Prospector tree. This indicates that the corridor regions in the junction need to be updated. You can update corridor regions in a junction manually, or you can specify that the junction object update corridor regions automatically.
When you update corridor regions in a junction, any manual edits that were made to the regions or targets within the junction corridor are lost.
To automatically update the corridor regions in a junction
- In Toolspace, on the Prospector tab, expand the Junctions collection. Right-click the junction. Click Update Regions Automatically. Note: When you toggle this option on, if Autodesk Civil 3D detects that changes have been made to the junction that require the corridor regions to be updated, then the update occurs immediately when you toggle the option on.
To manually update the corridor regions in a junction
- In Toolspace, on the Prospector tab, expand the Junctions collection. Right-click the junction. Click .
When the Update Regions and Rebuild Corridor command is invoked, the corridor region chainages in the junction are updated in order to stay in synchronization with the junction area geometry. The corridor properties are updated to reflect these new region chainage values.