A hybrid gravity and route choice model to assess vector traffic in large-scale road networks

TL;DR

This paper introduces a hybrid model combining gravity and route choice models to better predict long-distance road traffic flows, aiding disease and invasive species management in large-scale networks.

Contribution

It presents a novel hybrid modeling approach that improves flow predictions and route insights using limited survey data, addressing data collection challenges in large systems.

Findings

Achieved an R-squared of 0.73 for agent count predictions.

Reduced sampling effort needed for accurate flow estimation.

Provided detailed pathway predictions for long-distance travelers.

Abstract

Human traffic along roads can be a major vector for infectious diseases and invasive species. Though most road traffic is local, a small number of long-distance trips can suffice to move an invasion or disease front forward. Therefore, understanding how many agents travel over long distances and which routes they choose is key to successful management of diseases and invasions. Stochastic gravity models have been used to estimate the distribution of trips between origins and destinations of agents. However, in large-scale systems it is hard to collect the data required to fit these models, as the number of long-distance travellers is small, and origins and destinations can have multiple access points. Therefore, gravity models often provide only relative measures of the agent flow. Furthermore, gravity models yield no insights into which roads agents use. We resolve these issues by combining a stochastic gravity model with a stochastic route choice model. Our hybrid model can be fitted to survey data collected at roads that are used by many long-distance travellers. This decreases the sampling effort, allows us to obtain absolute predictions of both vector pressure and pathways, and permits rigorous model validation. After introducing our approach in general terms, we demonstrate its benefits by applying it to the potential invasion of zebra and quagga mussels (Dreissena spp.) to the Canadian province British Columbia. The model yields an R-squared value of 0.73 for variance-corrected agent counts at survey locations.