Mary's in the road.

Mary's in the road, Four times a day, Five times a week, She is always there, In snow or rain, Sunshine or sleet, Heavy goods or private car, No-one dares to move. Mary's in the road, Her banner held aloft, A modern sword of Damocles, Above their head. What strange legend or holy grail, Does it contain? None. It has just two words, But it concerns one hundred souls STOP CHILDREN!