This question is highly suitable based on the fact that dog ramps for car are mostly used outdoors. As such, many customers want to know this, based on the fact that they want to get a ramp with a surface that maintains its traction both while wet and dry. After all, no one would want to have a ramp but have to lift a dog just because it cannot enable the dog to maintain its grip after snowing or raining. So, ask this too and ensure that you get the one with a walking surface material that maintains its traction in all conditions.