I keep track of my commute mileage through the Georgia Commute Options website.
Recently, they have added a very nice GUI to their tool.
Now, I can create drag-and-drop objects of components of my commute. For example, see the entry for Saturday, 1/2/2014.
I believe the breakdown of the total commute, in terms of Carpool, Transit, Bicycle, etc., would provide some great information/data to the agency.
I love the enhancements.
Go Georgia Commute Options!