Sam was an old farmer. He was born on his farm and had lived on it all his life. He had married his neighbour's daughter, and they grew [bad word] and vegetables.
Sam got up at five o'clock every morning to gather them and take a load off to market in his old [bad word] 
There were very few vehicles on the country roads at that time of the morning, and Sam knew how to get to market very well, so as he was going along, he was always thinking about everything except his driving.
One morning he was thinking about what crops to plant for the next year's harvest, and whether to try something else. lot of other farmers were planting the same things which he produced, so the prices in the market [bad word] down and he was getting less money.
After a few kilometres, Sam came to a place where the small road which went in the direction of the market crossed a bigger one, and he continued over it without stopping. He always crossed the big road like that, because there was never any traffic on it at that time of the morning, so there was no fear of having an accident, and anyway he was always in a hurry, because he wanted to get to the market in time for its opening.
But this morning a young policeman whom he had never seen before  signalled to him to stop a hundred metres beyond the crossroads.
Sam stopped beside the policeman, and the policeman said to him, «Didn't you know that there was a sign telling you to stop at the crossroads before going over the main road?»
«Oh, yes,» answered Sam, «I knew that there was a sign at that point, because I go to market along this road every morning. But what I unfortunately didn't know was that you were here.»