No one knows better than you how your dog will handle the car ride. If your dog isn't a car kind of dog and you need to do some traveling to get to a dog-friendly hiking trail, focus first on training your dog to do well in cars. I can't teach you how to do that, but that's the first step you must take!
What I can tell you, though, is that you should NEVER leave your dog alone in the car if it can be reasonably avoided; especially not in the summer!
So, what do you do if you need to stop at the store, get dinner, or do something else on the way?
- If you plan on stopping at a friends...
Call ahead and let them know your dog will be with you. You can probably bring a least to set them up outside, or, they might have a fenced area you can use.
- If you need to go to the store...
If there's two of you, one stay in the car and one go in! If you ABSOLUTELY need to run in alone, leave the car running with AC if it's hot or heat if it's cold, and park close to the door so you can see the dog for as long as possible. You should avoid this if possible.
- If you decide to go out to eat...
It's best if you just don't. If you must, get takeout. Or, see if they have a dog friendly area. Or, eat sitting at the window next to your car and leave the car running as above. Mostly though, it's best to just get your food to go and stay with your pup.
Really, though, it's best to plan around your dog so that you don't put it into a compromising situation! It's like a child, so treat it like one!