English: The Car Dyke near Thurlby. The Car Dyke is a small fenland ditch with huge historical significance. It skirts the edge of the fenlands and is 122km long. It is generally accepted as having been dug in Roman times. It is likely that its purpose was to stop salt water inudation and help to drain land between the dyke and the edge of the fenland thus turning fens into highly productive agricultural land. More recent and much larger drainage schemes have turned almost the whole of the fens into agricultural land but the car dyke still serves a purpose as part of the fenland drainage system. The word "car" is a north Lincolnshire term for low lying land apt to be inundated by flooding or tides. The more generally recognised word "fen" is a south Lincolnshire term.