Sign on Rollercoaster

“What happened?” asked the hospital visitor of the heavily bandaged man sitting up in bed.”Well, I went down to Margate at the weekend and decided to take a ride on the roller coaster. As we came up to the top of the highest loop, I noticed a little sign by the side of the track. I tried to read it but it was very small and I couldn’t make it out. I was so curious that I decided to go round again, but we went by so quickly that I couldn’t see what the sign said. By now, I was determined to read that sign so I went round a third time. As we reached the top, I stood up in the car to get a better view.””And did you manage to see what the sign said this time?” asked the visitor.”Yes.””What did it say?””Don’t stand up in the car!”