Measuring Pedestrian Accessibility to Public Transport in Urban Areas: a GIS-based Discretisation Approach

The paper presents a GIS-based approach that can help practitioners in assessing pedestrian accessibility in urban areas, with a focus on accessibility to public transport stops and stations (nodes). This methodology represents an attempt to set up integrated approaches to urban planning and mobility planning, and provides a support in the decision-making process, with the dual aim of encouraging sustainable and non-motorised mobility and of improving public transport attractiveness. The proposed methodology is divided into three main steps: 1) Map the pedestrian permeability/impermeability of urban spaces around public transport nodes; 2) Discretisation of the map in a grid of 3m x 3m cells which attributes derive from the Topographic Database informative layers (DBT), and application of an algorithm to calculate the pedestrian access time to the public transport node; 3) Map of access times to create detailed pedestrian isochrones, and calculate how many residents (or how many opportunities and facilities) in the neighbourhood are well served by the public transport system to measure accessibility levels. The approach is applied to the case study of some metro stations in the city of Brescia, focusing on the different results obtained for the different urban forms that constitute the city (the modern city with open urban forms, the historical city centre and a residential neighbourhood). Finally, the paper provides a first comparison with similar results that can be obtained through vector-based tools that create isochrones from the road graph (e.g. Network Analyst tools).