answer:I think maybe you could mail an apology note, or just drop it off in his mailbox. One that’s short and to the point, maybe something like “When I backed out of my driveway, I didn’t see you. I just wanted to be sure you know I’m sorry and I promise to pay closer attention from now on. I’m so glad you didn’t get hurt and I hope there are no bad feelings.” I think you’re right about why he didn’t really acknowledge you. He probably had a lot of adrenaline pumping through him in the moment and just didn’t know how to handle it because he was overwhelmed. Now that he’s had a chance to calm down, he’ll most likely be much more receptive to your apology.