Maddiesmum - I know EXACTLY where you're coming from.
We live near a quite busy road, and Jameson was involved in an accident about 18 months ago (before we had him). His previous owner (our neighbour - very complicated) noticed he gone missing for 2 days and went out looking for him, yelling his name, and finally she heard distant meows from the shrublands (behind our gardens - a huge area of shrublands and gardens to hide/play/explore in). He was unwell and injured and she took him to the vets and he had to stay there overnight - he had a broken kneecap. He had to go back and forth to the vets while recovering.
To cut a long story short, since we adopted him I wanted to make sure he would avoid the road. I was told to take him near the road and when a car went past I'd shove him in the direction of our house and make a loud ''shhhhh'' ''psssst'' noise. So he would learn it is wrong to be near the road. We hadn't seen him near the road since, although he would sit at the front of the house, but not actually go near the road.
Until the other morning. I was up at 5am cos he was awake too and had been fighting the blinds for ages - sitting in the window seeming impatient and playful. I opened the flap for him, and let him out. The sensor lights on our side alleyway came on (the alleyway leads to front of house/road). I looked out the window (bedroom overlooking road) and saw him sitting by the road. I woke partner up saying J is sitting by the road. He wouldn't move for ages, and there were no cars. All of a sudden he just crossed and disappeared down the alleyway on the opposite side!! I don't know why he did it, but it seemed like he knew exactly where he was going. Also I have seen the fox (his friend) cross at the exact same spot before and go down the same alley way, so maybe this is something J has done before/does all the time!!
I could not convert him into being an indoor cat - that is just not possible, although I keep him indoors at night (it's actually not that hard).
I do think he is streetwise and very careful before crossing, but he is still a cat. I hope that from us teaching him ''bad road'' and him being involved in an accident at 6 months he should know, but maybe cats dont?