We travel back & forth to Florida yearly. It is a 2 day trip each way. No leash (my cat won't tolerate it), but I don't let the cat out of the car. I start out with her on my lap and when she is comfortable I let her roam the car. I have a litter box on the floor of the backseat and small covered containers of food & water. When we stop for gas/rest I take the covers off. She may/may not eat or relieve herself, but it's available. She does fine in the motel room, just bring in the food/water & litter box. Give her time to relieve herself in the a.m. We stack some boxes and I have a cat quilt (or use a towel) and invert a box top to make a bed of sort for her to rest on behind my seat. She likes to be up high. Do you have anything of your DS's that smells like him? The cat may be more comfortable laying on that. It may take a while but the cat will settle down.