步道是沿着河滨、溪谷、海岸、山脊、郊野或城区园林中等自然和人工廊道建设的、可供游人徒步穿越和骑车者骑行的户外绿色景观道路。国家步道系统法案规定:“创建步道系统的目的是为促进公众保护、使用、享受和欣赏国家自然和历史资源。”步道至少要50公里以上,最长的有数千公里。美国1921年最早设立第一条阿巴拉契亚国家步道,全程3575公里,穿越自然保护区、河流山脉、乡村小镇、高速公路等。美国国家步道分为景观步道、历史步 Trails are outdoor green landscape paths that are built around medium-nature and artificial corridors of riverside, valleys, coasts, ridges, countryside or urban gardens, and are accessible by foot and cyclists. The National Trail System Act states: “The Trail System was created to promote public protection, use, enjoyment and appreciation of the country’s natural and historical resources.” "Trails must be at least 50 kilometers long and up to thousands of kilometers long. The United States set up the first Appalachian National Trail in 1921, covering 3575 kilometers and crossing nature reserves, river ranges, rural towns and highways. American national trail is divided into landscape trails, historical steps