# A Novel Graph Neural Network Method for Traffic State Estimation with Directional Wave Awareness

## TL;DR

This paper introduces a new graph neural network method that improves traffic state estimation by incorporating traffic flow theory and directional wave awareness.

## Contribution

The novel physics-guided graph neural network integrates traffic flow theory and directional wave awareness for improved traffic state estimation.

## Key findings

- The model achieved higher accuracy than benchmark methods on a real-world highway dataset.
- Incorporating the fundamental diagram equation into the loss function improved physical consistency of estimations.

## Abstract

Traffic state estimation (TSE) is crucial for intelligent transportation systems, as it provides unobserved parameters for traffic management and control. In this paper, we propose a novel physics-guided graph neural network for TSE that integrates traffic flow theory into an estimation framework. First, we constructed wave-informed anisotropic temporal graphs to capture the time-delayed correlations across the road network, which were then merged with spatial graphs into a unified spatiotemporal structure for subsequent graph convolution operations. Then, we designed a four-layer diffusion graph convolutional network. Each layer is enhanced with squeeze-and-excitation attention mechanism to adaptively capture dynamic directional correlations. Furthermore, we introduced the fundamental diagram equation into the loss function, which guided the model toward physically consistent estimations. Experimental evaluations on a real-world highway dataset demonstrated that the proposed model achieved a higher accuracy than benchmark methods, confirming its effectiveness in capturing complex traffic dynamics.