LEMONS: An open-source platform to generate non-circuLar, anthropometry-based pEdestrian shapes and simulate their Mechanical interactiONS in two dimensions

TL;DR

LEMONS addresses the limitations of circular pedestrians in dense crowds by introducing anthropometry-based, elongated shapes and a physics-based 2D mechanical layer. The approach combines a Python generator that builds 2D/3D crowds from ANSURII data with a C++ engine that computes inter-agent and wall contacts via a damped spring and friction model, evolving the crowd via Newtonian dynamics. An XML-based configuration system and an online GUI enable easy crowd generation and integration with user-defined decisional layers. The method achieves higher packing densities (up to $7.2$ ped/m$^2$) and is demonstrated through a practical push scenario, with extensions to bicycles and potential future 3D expansion.

Abstract

To model dense crowds, the usual recourse to oversimplified (circular) pedestrian shapes and contact forces shows limitations. To help modellers overcome these limitations, we propose an open-source numerical tool. It consists of a Python library that generates 2D and 3D pedestrian crowds based on anthropometric data, and a C++ library that computes mechanical contacts with other agents and with obstacles, and evolves the crowd's configuration. Additionally, we provide an online platform with a user-friendly graphical interface for the Python library, and scripts to call the C++ library from Python. The tool enables users to implement their own decisional layer, i.e., to control the agents' choices of desired velocities.

Figures (11)

• Figure 1: Tightly packed random pedestrian disk arrangement, reaching a density of $4\text{ped}/\m^2$. The disk diameters are sampled from the empirical bideltoid breadth distribution of a US population subset (ANSURII database, ANSURII), with mean $49\cm$ and standard deviation $4\cm$. Algorithm details: App. \ref{['appendix:random_packing']}.
• Figure 2: Illustration of anthropometric measurements, including height, chest depth and bideltoid breadth, adapted from ANSURII.
• Figure 3: Torso section of a cryopreserved man, slice number $4405$, from the VisibleHumanProject database, covered with five disks. The 'Kodak Q-$13$ Gray Scale' ruler measures $20.3\cm$ by $2.5\cm$.
• Figure 4: Tight random packing of pedestrians without preferred orientation using an arrangement of five disks, reaching a density of $7.2\mathrm{ped}/\m^2$. Both the sample from the ANSURII database ANSURII and our model database have a mean bideltoid breadth of $49\cm$ and a mean chest depth of $25\cm$.
• Figure 5: Interactions between composite disks of pedestrians $i$ (radius $R_{s^{(i)}}$, velocity $\mathbf{v}_{s^{(i)}}$) and $j$ (radius $R_{s^{(j)}}$, stationary with $\mathbf{v}_{s^{(j)}}=\mathbf{0}$) are modeled using mechanical elements.