curb

Curb, or kerb in British English, is a raised edge that runs along the boundary between a street and a sidewalk or verge. It serves as a physical barrier to prevent vehicles from encroaching on pedestrian areas, provides structural support for pavement edges, and helps direct surface water into the drainage system. In modern road design, curb shapes and heights vary and are chosen to balance pedestrian protection with vehicle maneuverability. The term curb is the American spelling; kerb is common in the United Kingdom and other English-speaking countries.

Most curbs are made of concrete, although stone, brick, or precast concrete sections are used for decorative or historic streets. Common profiles include vertical curb (a sharp edge that supports the pavement edge), rolled curb (rounded top), and mountable curb (sloped, easier for vehicles to cross without damage). Curb-and-gutter systems channel rainwater to storm drains and help control road runoff.

In practice, curbs enable various street design features. Curb ramps provide wheelchair and stroller access between sidewalks and roadways. Curb extensions, or bulb-outs, shorten crossing distances and calm traffic near intersections. Curbside parking, bus stops, and protected bike lanes are often aligned with curb lines. Maintenance concerns include preventing spalling, cracking, and drainage blockages that can affect pedestrian safety and pavement performance.

Overall, curbs are a common element of urban and suburban streets, serving boundary definition, pedestrian protection, and drainage management.