This format can...
This format is designed to read the XML emitted when you tack "&output=js" onto the end of a Google Maps route URL (use the "link to this page" option to get a usable URL.) This allows you to plan a route using Google Maps, then download it and use it in your own mapping program or GPS receiver. To get a file suitable for use with GPSBabel, plan your route as usual with Google Maps. Once you've got it the way you want it, click the "Link to this page" link in the upper right-hand corner of the Google Maps page. Then, edit the URL that appears in your address bar by adding "&output=js" (without the quotes) onto the end. Hit enter, and the resulting page will be mostly empty. It doesn't look like much, but it contains exactly what GPSBabel needs. Save it to disk using whatever menu option your web browser provides.
Note that if you are using Microsoft Internet Explorer, you should make sure to save the web page as "Web Page, HTML Only". If you save it as "Web Page, Complete", it will be reformatted into a non-XHTML format that GPSBabel cannot read.
If you use a Unix-compatible operating system, this shell script might be useful:
#!/bin/sh FROM="233 S. Upper Wacker Dr, Chicago, IL" TO="1060 W. Addison St, Chicago, IL" wget -O - "http://maps.google.com/maps?q=$FROM to $TO&output=js" \ 2&>/dev/null >google_map.js gpsbabel -i google -f google_map.js -o gpx -F google_map.gpx