Systems engineering, central to manufacturing industry and, in its widest sense, universal to all effective practical and political aspects of life, is a term little understood by civil engineers and hence is not commonly applied to tunnelling (Muir Wood 1996). It is important to understand the concept, however, in order to appreciate its potential even if we do not immediately start as tunnellers to use the expression ‘systems engineering’. A more familiar term to the tunnel engineer is ‘design’ and if defined sufficiently broadly-as used in this book-‘design’ may be treated as synonymous to systems engineering.