Network resilience

From a network resilience point of view, the new bridge would leave Auckland transport in a more secure position than a tunnel.

A tunnel option would only provide additional network resilience for as long as the existing bridge remained operational (i.e., another 30-40 years).  After that, the net gain in network resilience would be zero, and the harbour crossing issue would only have to be solved again.

A new bridge could be future proofed against most of the factors that are likely to threaten network connectivity:

• physical impact from ships and other watercraft
• wind damage
• seismic activity

In general, bridges are at less risk than tunnels of being closed to traffic as a result of vehicle accidents, fire, flooding, failure of mechanical systems, and acts of malevolence.