Provide a variety of areas to rest and sleep, especially in elevated areas, like a sunny window, where they feel safe and can watch what's happening around them. (doylestownveterinaryhospital.com)
Yes, there are problems of the changing speed of the car due to the load, which is really bad especially if you are climbing elevated areas. (wannadrive.com)
Again, this is to gain a better view of their surroundings, but also very young kittens don't jump well so they often reach elevated areas by climbing. (catsexclusive.com)