A novel social distance model reveals the sidewall effect at bottlenecks

Xinyu Si,Lei Fang

doi:10.1038/s41598-021-00486-1

Abstract

Intermittent and periodic outbreaks of infectious diseases have had profound and lasting effects on societies throughout human history. During the global spread of SARS-CoV-2 and the resulting coronavirus disease (COVID-19), social distance has been imposed worldwide to limit the spread of the virus. An additional deliberate intention of keeping a minimum safety distance from neighbors can fundamentally alter the “social force” between individuals. Here, we introduce a new “social distance” term inspired by gas molecular dynamics and integrate it into an existing agent-based social force model to describe the dynamics of crowds under social-distanced conditions. The advantage of this “social distance” term over the simple increasing of the repulsive range of other alternatives is that the fundamental crowd properties are precisely described by our model parameters. We compare the new model with the Helbing and Molnar’s classical model and experimental data, and show that this new model is superior in reproducing experimental data. We demonstrate the usability of this model with a bottleneck motion base case. The new model shows that the bottleneck effect can be significantly alleviated through small wall modifications. Lastly, we explain the mechanism of this improvement and conclude that this improvement is due to spatial asymmetry.

Highlights

The third term, which is the new term that we introduce, describes the forces between individuals when social distance is imposed
We introduced a “social distance” term and integrated it into a widely accepted agent-based social force model to describe the movement of crowds under social-distanced conditions during the pandemic and post-pandemic periods
The advantage of this “social distance” term over the simple increasing of the repulsive range of other alternatives is that the fundamental crowd physics is precisely described by the model parameters offering the full flexibility in describing the different aspects of the social-distanced crowds

Summary

Introduction

The third term, which is the new term that we introduce, describes the forces between individuals when social distance is imposed. The advantage of our “social distance” term over the simple increasing of the repulsive range of any other potential function is that the fundamental physics is precisely described by the parameters (n, σ and ǫ ) in the quasi-L-J potential. Our “social distance” term offers the full flexibility of describing the different aspects of social-distanced crowds.

Results

Conclusion