The road is quite clean/clear.

• The road is quite clean, but the traffic is moving slowly. (這條道路相當乾淨，但車流移動緩慢) (正)。
• The road is quite clear, but the traffic is moving slowly. (這條道路相當暢通，但車流移動緩慢) (誤)。

解說：clean 表示道路乾淨的 (但不一定暢通，或許正在塞車中)；clear 表示道路暢通的 (但不一定乾淨)。