Use this demo to try the Routes API. The demo lets you specify an origin and destination as a latitude/longitude coordinates pair or as a place ID. Click a location on the map to copy the latitude/longitude coordinates to the clipboard, and then paste the location into the form.
If you have an encoded polyline or a GeoJSON linestring, and you'd like to view the polyline on map, go to Interactive polyline decoder utility.
After you select Get directions, the demo displays the response from the computeRoutes method as a route on the map.