Main Page | See live article | Alphabetical index . A curb extension marked by darkened tarmac and black posts on the left. A curb (or kerb) extension is a form of traffic calming used to facilitate pedestrian crossing of a street. Extending the curb into the street, provides visual clues of the need for traffic to slow down. Curb extensions are often used in combination with crosswalks or other markings. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.