Congratulations, that is great!
I went outside my zone on Sunday, too. I have been riding with a group since April, and have logged about 600 miles so far, mostly on country roads. Yesterday, I wanted to go out by myself, and measured a 20 mile loop which included about 5 miles of fairly heavily trafficked (is that a word?) highway. It was 9:30 in the morning, so traffic wasn't bad, but I was so proud of myself that I was able to do the loop and enjoy it.
Keep on riding!
That's Just How I Roll!
Aloha,
Southside Sally