Parking cul de sac

So I have been having problems with this neighbor. He runs a concrete business. He has about 4 big trucks. Before his coworkers would come in the morning and park in front of his house and gets in his truck to work. It would sometimes block the mailbox and I had a hard time getting in an out or waiting for them to get out of the way before I back out or drive in my driveway. They would park two perpendicular blocking my mailbox or parallel to it. I just finally got fed up with it because the mailmain refuses to get out of his car to deliver the mail. I call s usps and they told me legally no vehicle is suppose to block the mailbox because they don’t want to be responsible for driving too close and damaging the vehicles. I finally told me neighbor. Now he just drives to his coworkers place and picks them up I guess. So lately his wife again parks in front of my mailbox. I don’t want to be a Karen about it but what can I do about this?