Lucy has flat collars for every occasion but like others have mentioned they are just for show. I invested in two buddy belts (harnesses) and I can't be happier with them. I used to use the Sporn No pull harness until I can across the buddy belt. I use the buddy belt to walk Lucy and it is great to use in the car. I can secure the strap to secure her in the back seat right to the harness.
Google Spon no pull harness. If you want I think I have two possibly three laying around here I don't use any more. They are "gently" used--with some bully hair attached but if you are in a pinch they are yours. Just message me your address.