Transport Scotland is aware that there have been developments in the area of accessibility modelling and will be examining these in the near future.
A key benefit of the Accessibility Appraisal is that by looking at impacts on people, rather than transport systems, minority groups in society can be considered. Majority groups will have defined the current network coverage, since their needs are expressed through the demand for travel, and they create a market which will generally be catered for. Accessibility analysis is not restricted in this way and is equally appropriate for looking at the impacts of transport and land-use changes on minority groups. Social inclusion policy can therefore be informed by accessibility measures to ensure that all relevant people groups and trip purposes are considered.
There are potentially many hundreds of combinations of people groups, time of day, trip purpose and travel behaviour preferences which could be relevant to the analysis. It is not practical to look at all of these but rather to concentrate on those sections of society or those trip purposes that demonstrate the key impacts. Of particular importance is to optimise the choice of population sectors, geographical coverage, spatial detail, and trip purposes to reflect policy issues, which are sensitive locally. To ensure that social exclusion issues are considered properly analysis should consider:
In many circumstances access to local centres can act as a proxy for all these trip purposes obviating the need for separate analysis of each purpose. However, where there are local policy issues in relation to any of these trip purposes, such as local concern about access to a non centrally located hospital, then separate analysis of the trip purpose will be needed.
Although access to local amenities, work, health services and learning opportunities are all equally important with regards to the public transport network coverage, the following example focuses on access to employment opportunities.
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Employment Accessibility in Perth 'Equivalent Jobs' are the total number of jobs available across Scotland factored according to ease by which they can be reached, expressed in terms of a journey time deterrence function, from a given location. The underlying assumption in this analysis is that the total number of available jobs across Scotland in 2005 equates to ~2,2m (source TMfS/TELMoS). Applying the journey deterrence function to Perth for example indicates that the number of available equivalent jobs for residents of Perth travelling by car in the morning peak lies between 14,000 and 24,000. The analysis concludes that access to employment by car is greatest for people living in central and western areas of Perth and least for those living in the more rural eastern areas, including Scone. The scale below is applied when looking specifically at the ratio of car to public transport equivalent available jobs: Very Low:          100-400 (i.e. up to 400 times more jobs available by car than public transport)
Low:Â Â Â Â Â Â Â Â Â Â Â Â Â
Average            High                1000-1300 Very High         1300-1600 The following map has been created using TMfS and TELMOS. The diagram illustrates the ratio of car to public transport employment accessibility for people resident in Perth during the AM peak period in 2005.
This illustrates the distribution of relative car 'dependency' for access to employment across Perth, reinforcing the conclusion that the more rural eastern areas of Perth are more car dependant in these terms than central and western areas. |
The level and detail of the analysis needs to be commensurate with the scale of the problem and the extent to which the options are likely to impact on network coverage. To undertake the analysis there are four main steps:
(i) Obtain information on the locations where work, education, shopping, health and leisure facilities are available as appropriate;
(ii) Estimate perceived travel times by public transport across the potential area of impact for the do-minimum situation and for each option;
(iii) Calculate and map how effectively the public transport system meets people's needs including comparisons with car travel times for the do-minimum situation and for each option. The results of the do-minimum analysis should be included in the background information section of the AST under "Social Context";
(iv) Present results of changes in accessibility in terms of number of people affected, aggregate changes in indices, or for more sophisticated analysis, changes in utility (see Section 17.3 - Modelling and Assessment Software).
