Abstract: A barrier is comprised of a plurality of hollow shaped bodies of plastic material and each shaped body comprises a wide base portion having a bearing face supporting the shaped body on a surface and a narrower upper portion, the wide base and narrower upper portions having two side walls, the portions of the side walls of the upper portion merging into the portions of the side walls of the base portion. Respective partially cylindrical end faces extend between the side walls, the end face at one end of the shaped body being convex and the end face at an opposite end being correspondingly concave whereby adjacent end faces of successive ones of the shaped bodies in the barrier mate with each other.