That is vvvveeeerrrrrrry interesting Tamsyn.
So if anyone else wants to waste a bit of time...
I thought I'd look at the bike paths (not that I have a bicycle, just a motorcycle).
Well, I ended up with .shp files, which I've never seen before.
Knowing google is my friend, I did a bit of research.
Long story short, I was able to view the files on Ubuntu Linux by downloading and running QGIS (totally free).
http://www.gislounge.com/introducing-the-quantum-gis-ecosystem/
It appears to be a comprehensive, user-friendly (I could do what I wanted to) GIS GUI.
All platforms seem catered for -except maybe those of the fruit variety.
The manual is a PDF, which I easily searched for '.shp' and found instructions on how to load such files.
If I can do it, anyone can.
Hope that is of use to someone.
But if you have a better free program for the purpose, let us know.
Ken.