The list of bridges was compiled by hand based on 1980 road atlases. 64 counties are shown on an equal land area map - software written by the author on an Archimedes computer.
Most major rivers and estuaries are frequently spanned by bridges or tunnels. These links are as important as shared boundaries to the geographical contiguity of the country. They are implemented in the matrices used to create all the cartograms shown in the rest of this dissertation.