Measuring Accessibility using Gravity and Radiation Models

TL;DR

This paper compares gravity and radiation models in assessing transportation accessibility and policy impacts, using a case study of a new bus system in Teresina, Brazil, to evaluate their accuracy and differences.

Contribution

It introduces a novel comparison of gravity and radiation models in policy testing scenarios, specifically analyzing the impact of a new transportation network.

Findings

Both models effectively estimate trip distribution changes.

Differences in model predictions reveal underlying assumptions.

Models provide complementary insights into accessibility impacts.

Abstract

Since the presentation of the Radiation Model, much work has been done to compare its findings with those obtained from Gravitational Models. These comparisons always aim at measuring the accuracy with which the models reproduce the mobility described by origin-destination matrices. This has been done at different spatial scales using different datasets, and several versions of the models have been proposed to adjust to various spatial systems. However the models, to our knowledge, have never been compared with respect to policy testing scenarios. For this reason, here we use the models to analyze the impact of the introduction of a new transportation network, a Bus Rapid Transport system, in the city of Teresina in Brazil. We do this by measuring the estimated variation in the trip distribution, and formulate an accessibility to employment indicator for the different zones of the city. By comparing the results obtained with the two approaches, we are able, not only to better assess the goodness of fit and the impact of this intervention, but also to understand reasons for the systematic similarities and differences in their predictions.