I know how you feel. We had a dog which was so scared of cars, he would not even walk on the roadside of the pavement. He was shaking and sick within 20 minutes when in the car. It took patience. At lunchtime when my husband came home I used to carry(.!) Taffy into the car and sit with him for 10 minutes - no engine. After a few weeks of this I sat there with the engine running. In the evenng we drove him round the block. On trips with the caravan, I sat next to him in the car with a sicky-bowl, tissues etc. I let him be sick while massaging his neck. To cut a long story short. It worked and after a year (I said, patience is needed), this same dog would hang out of the window by his toenails to shout abuse at the village dogs whenever we went to the South of France. We lived in Belgium at the time- a 1000 kms away from the South. No more problems - a delightful dog and worth the effort- alas he is no more.
Helen