Universality in multispecies urban traffic.

Area of Science:

• Physics of complex systems
• Traffic flow dynamics
• Urban mobility studies

Background:

• Vulnerable road users like motorcyclists and cyclists face safety concerns in mixed traffic.
• Limited theoretical frameworks exist for multispecies traffic flow, especially involving new micromobilities.
• Understanding microscopic behaviors is crucial for macroscopic traffic theory.

Purpose of the Study:

• To establish a physics-based understanding of collective phenomena in mixed traffic.
• To identify and quantify relationships between maneuverability, speed, and traffic states.
• To develop a theoretical model linking microscopic interactions to macroscopic traffic behavior.

Main Methods:

• Analysis of the pNEUMA dataset for real-world traffic data.
• Establishing a nonlinear relationship between maneuverability and speed, linked to nonequilibrium sample space reducing processes (SSR).
• Coupling SSR with Newell's nonlinear traffic model to derive power-law relationships and conduct simulations.

Main Results:

• A nonlinear relationship between maneuverability and speed was identified.
• A power-law relationship was found between average maneuverability (temperature) and mean speed difference between motorcycles and cars.
• A nonequilibrium phase transition from ordered lane formation to disordered cluster formation was observed, governed by a universal scaling exponent.

Conclusions:

• The study provides a theoretical foundation for multispecies traffic flow.
• Microscopic behaviors in mixed traffic exhibit universal scaling laws, linking to percolation theory.
• Findings enhance understanding of urban road safety for vulnerable road users and inform traffic management strategies.