Once you’ve clicked the map image, click the button to the right of the ’Add Layer’ and ’Share’ buttons.
From the drop-down menu, choose ’Export to KML’
You’ll be asked whether you want to save the entire map, or just the route file. Click the route option from the drop-down list.
Then click ’Download’
You’ll be asked whether you want to save the file, or whether you want to open it immediately with Google Earth. (Google Earth must be installed on your device)
Make your choice and download the file.