^^That is the dumbest thing I've ever heard.
Anyway, to answer the OP. First off, Buster was an absolutely adorable Australian Cattle Dog mix! I think the only genes he got from his Cocker mom was the drop ear.
Second, you can train dogs to stay away from the road. My grandmother had a farm while I was growing up and all of her dogs were outside only, never tethered, etc. She'd had everything from random mutts, to an American Eskimo, to a Border Collie and a Lab. The Border Collie was the only one to actually make it long enough to die of old age though. The Eskie came close, but slid on the ice one year right out onto the road and just the wrong time. So you have to understand that while you can train a dog to stay out of the road, you're always going to have that risk that one time, they'll break their training and that will be the one time they get hit. You can minimize the risk by installing an invisible boundary fence along the front of the property by the road and training them to that, assuming the dog won't one day try to follow the fence to it's end point.
It's a calculated risk, having loose working dogs and living by a busy road. I'm sure that the OP and their family will be outside most of the day like any farmer, so the dog will have plenty of attention and interaction?
I would stick with either herders (easy to train, less likely to go wandering off) and livestock guardian dogs like Pyrenees, etc. They stick with their charges for the most part and aren't usually too inclined to go wandering about. They can, however, misinterpret things, like cars, as threats and move to deal with it in their way. In the case of dog vs. car though, car will always win.