Objects in image: Poster
Text visible in image: WARNING, PENALTY, FARES, Have, you, paid?, Please, buy, your, ticket, before, you, travel,, otherwise, you, may, have, to, pay, a, Penalty, Fare, (at, least, £20)., produce, when, asked, twice, valid, ticket, your, entire, journey,, fare, Ifyou, can, travel, lsingle, station, permit, charged, (whicheve, your, train, the, greater, amount), continue, station, which, single, fare, the, same, train., journey, Mintht.
Question: what is the sign warning us on?
Answers: have you paid?, have you paid?, penalty fares, penalty fares, to pay for fare, penalty fares, not paying, have you paid, have you paid?, paying for a ticket