What age do you let your daughter ride her bike alone around the nieghborhood?

[TaylorSmiley]

We live near a very busy street that is behind our house (We, as a family, do not cross the street walking ever because it is way to busy), the subdivision we live in is fairly safe as far as cars,etc with the exception of cars cutting through because of the busy street and the church that is down the block. As far as crime rate and things like that, we remain pretty safe, although we know there are no guarantees on that either. My daughter is 10 almost 11 and pretty responsible , but she wants to ride to her friends house, but I am unsure that we are ready to do that. She has just recently been practicing staying home by herself for 15 minutes while I take the other children around the block and things and she takes the babysitting course, but I do not know that I am ready for her to ride all over town because of that very busy street. I am looking for feedback...thanks!