We were driving home from our local Renaissance Festival and we were about 20 minutes in to our 2 hour drive home. It was around 7:30pm so the sun was setting and you could still see into people's vehicles. My wife must have been horny after drinking all day and having her tits mostly exposed. She reached over and started to play with my cock as I drove. In turn, I reached over and pulled her tits free of her camisole. She reclined the seat slightly so her face was blocked by the pillar of the car but her tits were in plain view. She jerked me off as I fondled her tits. Being on the interstate, it wasnt long before we came up to the first semi-truck. I knew what I wanted to do and my wife was just tipsy enough and horny not to object. We pulled up next to the cab and as slowly as I could, we passed him. I made a lot of motion with my free hand as I jiggled her tits and squeezed them at the base to push her tits higher, her hard pink nipples poking straight up. She gripped my cock tightly as we crept by after realising what I was doing. She laughed and playfully slapped my hand but she did not stop me. I pulled in front of the truck after passing him and he flashed us back with his lights. This contiuned with every truck we passed for about 40 minutes before I convinced her she should play with herself and cum. It was darker out now and only the street lights were illuminating the inside of our vehicle so she didn't hesitate. It didnt take long before she was starting to cum as we were right beside another semi-truck. I came when she did and it was one of the most fun things we had done together in a while.