Traveling with roasted duck

If you'll be taking the duck straight from the oven to the car and serving it soon after you arrive, you should be okay from a food safety standpoint. I'd try the cooler method, and then pop it back in a hot oven when you get to your destination for about 15 minutes to re-crisp the skin. Good luck!

As the bird flies. You will get there faster.

For a shorter trip, I would recommend Tom Hirschfeld's tip of keeping a turkey warm in cooler (http://food52.com/blog/4837-tom-s-no-sweat-rules-of-the-thanksgiving-road) - but 40 minutes seems like a long trip, and would have me concerned from a food safety standpoint. Hopefully a food safety expert will weigh in, but if you can't cook it there, it seems like you might need to cook it, refrigerate it, and then reheat it at your destination.