The double-coated tarp California Highway by Outwell is tailored to all bus tents bearing the same name. Thus, the tent completely covers the tarp and you do not run the risk of having any rainwater between the tarp and your tent's floor.
The footprint serves as a guarding layer to keep your tent's floor free from dirt and abrasion. At low temperatures, it is also a welcome insulation. For a perfect fit, the tarp comes with pegs to fix it to the ground.