Outside by leash access only? I know it's sad to listen to the meowing, but she'll eventually learn that outside is a no-no, or is only under certain conditions. I think the best solution is to ignore her crying. Maybe when you leave you should put her in another room and close the door, so she cannot charge the door? Do you have a room or connections of rooms you could close her off in when you all are leaving? Something big enough so she won't feel trapped? Or perhaps build an outside enclosure which is accessible by an outside covered run, just like PIF suggested? I really think you should be super careful because you live by a highway, but you know that, as is obvious in your post.