also: とうはんしゃせん
noun
climbing lane; crawler lane
A designated lane on an uphill slope for slower vehicles, allowing faster traffic to pass. Common on expressways and mountain roads.
この先、登坂車線がありますので、遅い車は左側へどうぞ。
There is a climbing lane ahead; slower vehicles please keep left.
登坂車
I overtook a truck in the climbing lane.