This report has defined accessibility as ‘the ease with which activities, either economic or social, can be reached or accessed by people’. Therefore, accessibility assessment is the measurement of how easy it is for an individual to participate in desired activities, based on a set of measurable factors, including mode and destination choice.
Accessibility is concerned with both the land use and the transport systems, and provides an integrated way of measuring changes in either system.
Measuring accessibility not only provides a more realistic representation of the transportation world (including those that may be transport disadvantaged); but accessibility also provides a better measure when considering the long-term sustainability of the transportation network. This is because unlike traditional transportation modelling that typically only models mobility using one or maybe two modes of transport (such as motorised vehicles and public transport), accessibility modelling evaluates all modes. This includes the traditional modes of transport as well as more sustainable modes of transport such as public transport, walking and cycling. Accessibility modelling also includes the various interchanges between these modes such as walk-public transport-walk, car-walk, cycle-public transport-cycle-walk and so on.
The quantification of accessibility provides:
· the ability to look at the impact of people’s capabilities on the level of access they experience
· the effect of spatial factors in land use planning
· new forecasting indicators upon which decision makers can make better informed and optimum decisions
· a method to consider changes in accessibility due to changing demographics
· a method to test changes in land use, transport networks, services and destinations
· a greater level of analysis whereby those being consulted can appreciate that decision makers are considering all perspectives
· more information about how users perceive transport opportunities
· better presentation methods to show expected outcomes from recommendations.
There are five key properties that accessibility metrics should possess. The metrics derived from this research are considered to have met these criteria. These include (adapted from Davidson 2009):
· Consistency: if there is no real change in the system, then the indicator should not change. If there is real change in the system then it should change.
· Ordinality: an improvement to the system should result in a change to the indicator in a particular direction. Further improvement should result in a greater change to the indicator in the same direction.
· Linearity: in order to be properly useful in looking at trade-offs in projects, or knowing how much better one project is than another, the indicator must also be a linear measure. Linearity is required whenever indicators are to be combined.
· Meaningfulness: units should be a meaningful measure of the system being described.
· Transferability: the indicator must be able to be moved from city to town and preferably rural areas as well and still remain relevant and comparable between locations.