Using Lorenz curves to assess public transport equity

Equity has been a major concern of public transport provision and is required by legislation in many countries. Several approaches measure equity in transit supply however none produce a simple system-wide measure of equity performance. A new approach is presented using Lorenz curves to measure the relative supply of transit to the population. Gini coefficients provide a single measure of overall equity using this method. A system-wide assessment of overall transit supply to the population in Melbourne, Australia shows that 70% of the population shares only 19% of the supply (Gini coefficient = .68). When employment is also taken into account, the situation is not much different; 70% of jobs and population share 23% of service (G = .62). In order to gain some understanding of vertical equity, the transit supply was compared between different age, income and vehicle ownership groups. There is some evidence of higher supply for youth and low-income groups in inner Melbourne, and in all parts of Melbourne no-vehicle households lived in areas of higher transit supply. Overall it is unclear how “fair” these distributions are compared to equity in other cities since this is the first time this method has been undertaken. Projects using similar approaches should provide a good basis for establishing comparative equity between cities.

► Lorenz curves are a very convenient way of assessing public transport outcomes within cities.
► When applied to Melbourne this technique shows 70% of the population has convenient access to just 19% of public transport supply.
► When jobs are included in calculation, 70% of jobs and population has convenient access to just 23% of supply.
► The technique also can estimate differences in vertical equity distribution by socio-economic group and by location.