It was an objective of this research to answer the question ‘what is accessibility and how might it be measured and quantified in New Zealand?’ Accessibility (and accessible) is often a confusing term because it is sometimes used to describe when access is or is not achieved for people with mobility or sight impairment, eg to a building, and it is often used to infer the ease of reach to a certain destination, eg to a location via a particular mode of transport that might be some distance away.
This research is concerned with the wider definition of accessibility and although one element is ‘capability’, eg a barrier that might restrict access to people with mobility or sight impairment, there are two other elements, ‘opportunity’ and ‘mobility’, that need to exist for true accessibility to be present. It is when these three dimensions are present that accessibility can be understood, measured and quantified.
This research proposes that accessibility in New Zealand is defined as ‘The ease with which activities, either economic or social, can be reached or accessed by people’.
The research has been prepared against a background of UK and European, and to a lesser extent US and Australian experience. These overseas experiences have been compared with existing New Zealand policy, practices, capability, need and data. An overriding conclusion of the research is that by better understanding accessibility there is the potential for a step-wise improvement for how transportation and land use can be better managed and integrated. Improved understanding of accessibility also has the potential to guide policy makers to deliver improved accessibility both by clarifying current implicit accessibility policy, and by setting out new explicit policies – accessibility also needs to be considered as its own area of study.
The research has identified that traditional transport demand models do not answer all the questions required of today’s decision makers, and accessibility assessment (and specifically accessibility modelling and analysis) provides a new perspective for old problems. Consequently the research includes a methodology to quantitatively measure accessibility that takes into consideration different modes of travel (walk, cycle, private motor vehicle etc), travel behaviour (logistic decay functions), destinations (origin or destination based), activities (consumed or supplied) and multiple opportunities (saturations). The research also describes the different types of indicators such as threshold, continuous and composite indicators and the audiences most suited to each indicator type.
Although accessibility modelling calculations can be undertaken manually, given the range of potential travel that accessibility modelling attempts to assesses, ie what travel ‘could’ be undertaken rather than ‘would’ be taken, the calculations are best automated within a computer. Given the need for specialised software to undertake these types of calculations various overseas programs were examined and one program briefly tested. It was concluded that given New Zealand’s data constraints, the spatial nature of the calculations and the flexibility provided by geographic information systems (GIS), the research settled on a GIS providing the best overall solution and hosting location for the resulting calculations and maps.
Consequently the pilot accessibility assessment of Christchurch, New Zealand was undertaken within a GIS and the various calculation methods and scenarios examined to understand the responsiveness of the proposed accessibility methodology to change. This included measuring the change in accessibility with the addition of a new land use, ie a new hospital, and the change in accessibility with the addition of new infrastructure, eg a new pedestrian, cyclist and vehicular bridge. This also showed the spatial scalability of a GIS where the methodology can be run at both a meshblock (a group of households) and an individual (household) level without modification.
Given the new and evolving nature of accessibility assessments the study identified a number of potential areas for refinement and further research. These are broadly categorised into two types of recommendations: management and delivery; and development and refinement. Even so, and given the number of recommendations will take several years to implement, the majority of the New Zealand accessibility analysis methodology included in the research is suitably refined for use by practitioners, today.