The document reports the state of traffic calming programs in the United States. It also includes historical information about programs in other countries. For the purposes of this report, traffic calming involves changes in street alignment, installation of barriers, and other physical measures to reduce traffic speeds and cut-through volumes in the interest of street safety, livability, and other public purposes. This report focuses mainly on physical measures, including street closures and other volume controls under the traffic calming umbrella. Education and enforcement activities, such as neighborhood traffic safety campaigns, fall outside the umbrella but will be mentioned where relevant.