All paths, except those created using Guided Drive, are stored as a series of target points through which the vehicle is required to drive. Autodesk Vehicle Tracking allows you to move the target points of a path, dynamically updating the path to reflect changes in position.
If you edit the path in such a way that the vehicle cannot get from a given point to the next target, the remainder of the path will draw as a single line (red by default).
To open the Edit Tools toolbar, click Edit Tools on the Vehicle Tracking toolbar.