Car Desensitization – Help Needed

My 2‑year‑old rescue really dislikes car rides. When I first got him last year he would throw up almost every time we drove, but now he mostly just pants and looks stressed. Because 99% of his rides are a 2‑minute trip to the park, I’ve never really put in the time to acclimatize him and have been relying on a covered crate to get him through short rides.

A long drive home for Thanksgiving made it very clear he isn’t coping well with the car, and it convinced me that the only way he’ll ever be comfortable is if I properly desensitize him. I’ve now made it my mission for the next 2–3 months. I’ve also decided to stop using the crate and instead teach him to relax on a dog bed. I have a rear seat delete in the cab of my truck, so there’s enough room for a full dog bed, and he’s never loved the crate anyway.

Progress so far

I’m on week two of this and so far he has had no issues staying calm with the engine on. I’ve been feeding him his meals in the parked car and also spending about 30 minutes a day giving him a pupsicle or elk antler on his bed with the engine running.

Questions about training/management

1. ⁠The moment I back out of the driveway he forgets what he’s doing and goes straight to the window. Is that a sign that I’ve moved too fast in the training, or is it normal for dogs to look out the window? For those of you with car‑comfortable dogs, what does “relaxed in the car” actually look like?

2. ⁠When I strap his harness in, should I give him only enough slack to lie down fully on the bed, or enough that he can stand and look out the window? I’m hesitant about the latter since movement and engine noise seem to make him more amped up.

Thank you!