prefetchedAreaAlongRoute

Important: This is a Public Preview API. It may be changed or removed at any time. Area along the active route to prefetch navigation map data and keep it available. If the parameter is omitted, the default area along the active route will be used. If the parameter is set to null, NO navigation map data along the active route will be prefetched. The larger the area, the more robust the system is to temporary unavailability of the map data source, but at a greater memory and bandwidth cost. The parameter defaults to DEFAULT_AREA_ALONG_ROUTE meters.