Integrated Wellington region land transport resilience study

Wellington region’s transport network has poor resilience to natural hazards, given the rugged terrain, high seismicity and wet climate.  This exposes the land access to the region and the capital city to be potentially cut off from the rest of New Zealand for several months, and its cities to be isolated from each other.  This paper reports on a pioneering integrated resilience study of the entire land transport system in the region provided by the state highways, principal and arterial local roads and the railway system.  The study considered resilience risks from a range of natural hazards (earthquake, storm and tsunami) using the metrics of availability and outage. The resilience risks and the relative importance of the routes were used to assess the criticality of these risks for future investment in resilience enhancement.  The criticality also considered risks to other lifeline utilities - power, water and telecommunications that share these transport corridors. The combined criticality was used to prioritise these resilience risks. The highest criticality resilience risks were classified into extreme, very high and high levels. The extreme criticality risks identified were the state highway between Ngauranga and Petone and the adjacent Ngauranga interchange between the two State Highways 1 and 2, which together provide access between Wellington, Hutt and Porirua cities. A range of very high risks were identified across the region which included both state highways and local roads.  This novel resilience study provided the basis for a subsequent business case for future investment to enhance the resilience of the region’s transport network.