And while it is being built, it will temporarily cause even more problems for traffic, as some streets will be closed off.

closed 是动词 close 的过去分词形式，表示"关闭"的状态。 off 在这里是副词，表示"完全地、彻底地"的意思。 closed off 是一个短语动词，表示"完全封闭、禁止通行"的意思，常用于描述道路或区域的封闭状态。