I was faced with the same problem. With my previous cats the road wasn't nearly as busy and as the volume increased they adjusted to the situation.

However these two little chaps wouldn't have much of a chance. If I could guarantee they would stay in my back garden or jump the fence into the very large playing fields at the back of our house I would let them out.

I am fortunate in that we have room for an outdoor pen, I call it a play pen because that's what they do play and lounge in it.

In fairness Sooty is itching to get outside to explore. I have cat harnesses and I take them into the back garden regularly. I can't take them any further because of loose dogs in our area. If they weren't harnessed they could climb a tree.

Sue