The Terrain
When roads are built by engineers with capital to support their work, they are successfully able to build roads across difficult soils. Modern road builders have less need to seek out easy geological conditions. When roads were made not by civil engineers but by people walking on the ground, the road followed the soils which were found to be easiest under foot. The A151 passes across two types of country, the upland and the fen. The highest point on it lies within a kilometre of its western end at 123 metres above mean sea level. It then passes across a gently sloping dissected plateau of Jurassic rocks capped in its highest parts by glacial clay. After about 16 kilometres, it enters the fen and is soon at about two metres, rising to three, nearer the coast.
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