This command is used to extend the length of a straight or curved section of track.
The selected endpoint determines the position and angle of the first endpoint of the new track. The cursor is dragged to set the second endpoint. A curved or straight track will be created, depending on the position of the second endpoint.
If easements (Section 2.10.4) are enabled then an easement curve will be generated (if required) to connect the old and new tracks.
For detail about;