Analysis of traffic characteristics in mixed road environments based on a unified lattice hydrodynamic model

Mountainous urban road networks feature complex geometries, including straight, curved, and sloped segments, which jointly impact traffic dynamics. Given the critical role of traffic stability in ensuring safety and efficiency in such settings, this study examines how road geometry affects traffic stability and flow under minor disturbances. We develop a unified lattice hydrodynamic model integrating straight, curved, and sloped segments, and conduct linear and nonlinear analyses. Our results reveal that roads with a higher proportion of curves and smaller turning radii enhance traffic stability. Conversely, while roads with more curves and larger radii are more vulnerable to disruptions, they enable higher traffic flux. This paradox stems from lower speeds on smaller-radius curves dampening disturbance impacts, whereas higher speeds on larger-radius curves, beneficial for flow, increase traffic sensitivity to perturbations. The study further shows that adjusting road segment proportions, turning radii, and gradients optimizes traffic stability and flow. Numerical simulations validate these findings, and VT-Micro model data confirm that road geometry adjustments reduce fuel consumption and emissions. This research provides practical guidance for mountainous urban road design and offers new insights into traffic management in complex road environments, balancing efficiency and environmental sustainability. Graphical Abstract