If your site creates barriers for the system map, whenever an itinerary is generated, it takes into account the limitations of those existing barriers and produces itineraries that take the client around the physical obstacle.
For example, you may have set your parameters to look for stops that are within half a mile of the destination. However, if a stop exists within a half mile radius but causes the client to cross barriers such as a major freeway or waterway then those stops are excluded from the results.
