Railway Act Article 49

Passengers riding without tickets or holding invalid tickets shall repurchase tickets and may be charged an additional 50% of the original price, unless valid reasons exist.Railway institutions may examine the shipper’s freight if the name, character or magnitude reported is questionable. In case of examinations resulting in inconformity and causing the freight transportation fees to be undercharged, a supplement of not more than four times the difference shall be charged.
中文原文 鐵路法第49條
旅客無票乘車或持用失效乘車票,應補收票價;如無正當理由者,並得加收百分之五十之票價。
運送物之名稱、性質或數量,如鐵路機構對託運人之申報有疑義時,得檢驗之;檢驗不符,因而致運費不足者,補收四倍以下之差額。

English translation for reference only; the Chinese text prevails. Not legal advice.