The designers are re-imagining the city's public transportation system.

re-imagining 是动词 re-imagine 的现在分词形式。re-imagine 由前缀 re-（表示“重新”）和动词 imagine（想象、构想）组成，意思是“重新构想、重新设想”。re-imagining 指的是“重新构想”的动作或过程。