Today I drove 500 miles with the fixed gear tied to a roof rack. Didn't have any issues with the bike getting loose, but i'd like to not do that again. A standard bike rack won't fit. Will have to look into a roof rack mount maybe.
Was a good vacation though, did 25 miles at 17.9 mph one day, and a total of 92 miles.
Also, my six year old road a 2 wheel bike without training wheels for the first time! He literally jumped on the bike and took off with no problem. Proud dad moment for sure!
Dave