It is an argument that has been made for the last 70 years, during which time countless other road networks have been extended, tube lines tunnelled, wobbly bridges built and novelty cable cars erected.
Special attention is focused on the restoration of the L Line Tunnel, which was flooded by Hurricane Sandy.
Mr Keith explained that the intended targets were revealed in a note inside Lindsay's passport, found in a Piccadilly line tunnel.
Transit officials estimated that 1,000 feet of the No. 1 subway line tunnel beneath the World Trade Center, including the Cortlandt Street station, had collapsed.
As built, for ease of passenger access, the branch's northbound tunnel ended in a dead-end platform adjacent to the northbound main line platform with the branch's southbound tunnel connected to the northbound main line tunnel.
The disused Jubilee line tunnels would be enlarged to accommodate the larger DLR trains and Aldwych station would form the basis for a new station on the line, although requiring considerable reconstruction to accommodate escalators.
In September 1938, during the Sudeten Crisis, when war appeared imminent, the Bakerloo and Northern line tunnels at Embankment were temporarily sealed with concrete to protect against flooding through bombing.
The lines, tunnels and bridges were repaired and rebuilt by hand.
For lined tunnels with a drainage layer, the reverse is true.
Deep in the French chalk are hundreds of kilometres of tunnels — straight-line tunnels, curvilinear tunnels, tunnels on various levels crisscrossing other tunnels — holding more than a billion bottles of champagne.
