Which are stronger concrete or plastic wheel stops for carparks?

While concrete wheel stops may be perceived to be stronger because they are heavy and concrete is considered to be a structural material, the reality is that concrete is the worst possible material to use for wheel stops due to its lack of flexibility.

Plastic wheel stops and also rubber have the ability to absorb the repeated impact of vehicles running up to them that would otherwise snap a concrete wheel stop particularly where they are weakest through the fixing holes.

To compensate for this inherent weakness the manufacturers of concrete wheel stops tend to make them higher to gain more strength, unfortunately this then makes them too high and non-compliant with the relevant standards.

So the short answer? Plastic followed by rubber.