Curbing

Curbing has both a physical and a figurative sense. In civil engineering and urban design, a curb is the raised edge that separates a street from the sidewalk. The process of installing or maintaining this feature is called curbing.

Curbing serves several purposes: defining traffic boundaries, supporting drainage through adjacent gutters, protecting pedestrians, and guiding wheel paths for vehicles and accessibility ramps. Curb profiles vary: standard or barrier curbs with a sharp or vertical face; mountable curbs with rounded profiles intended to be traversed by vehicles; and lesser-used integral or dropped curbs for transitions. Materials are primarily concrete, but stone, brick, or asphalt can be used.

Beyond streets, curbing denotes edging used in landscaping to separate lawns, flower beds, and walkways. Concrete is common, though plastic, metal, or natural stone edging also appears.

Metaphorically, curb is a verb meaning to restrain or limit: governments may curb spending, curb inflation, or curb emissions.

Note on spelling: curb is American English; kerb is the preferred form in British English and many Commonwealth varieties.