Put the mattress on top of the car and rope so that it goes length wise with the length of the car see pics above.
Mattress and box spring on top of car.
If so how would be the best way of strapping it down.
Secure your mattress to the top of the car.
You can use a plastic mattress cover to prevent your mattress from collecting dirt and permanent stains.
Still there is a basic method to follow when tying a mattress to the roof of a car.
Buy sturdy rope nylon or polyester based.
Toss the first long piece of rope over the length of the mattress.
Do you think it is safe and or possible to move a queen size mattress on top of it.
I have a hyundai accent and need to move a queen size mattress and box spring 50 miles.
During the process of being moved the sides and top of your mattress may come in contact with floors stairs the ground outside and the inside of a moving van or the top of your car.
I ve moved a full size mattress on top of the car before easily.
In addition keep an eye on the mattress so you notice if it starts to slip a rope comes loose or the plastic breaks.
There should be enough to secure one end under the front of your car and enough at the other end to secure the second end under the back of your car.