4. Techniques for distributional impact assessment

The assessment of distributional or equity effects should be evidence-based. There are various qualitative and quantitative techniques for assessing equity impacts. These include:

• Indexes to measure equity or inequity between groups or populations have been widely used in the appraisal of transport initiatives. The Gini index is the most well-known and used equity index. However, this index provides information about income inequality across society as a whole. It will not be relevant for assessing transport initiatives.
• Equity weights provide a method of explicitly incorporating concepts of fairness into economic analysis.
• Social Impact Assessment (SIA) is perhaps the most common technique to identify social impacts of transport initiatives on the community. Derivatives of SIA include Social (equity) Impact Assessment and Cumulative Impact Statements.
• Stated preference surveys can be used to inform equity evaluations.
• Spatially based analysis (commonly undertaken with Geographic Information Systems (GIS) technology) is becoming an important tool to identify equity impacts resulting from transport initiatives.
• Micro-simulation is another analysis/modelling approach for exploring distributional and equity issues by focusing on personal attributes across individuals in the population.

These are discussed in more detail in Appendix B.