Traffic and Granular Flow 2024

The 15th edition of the Traffic and Granular Flow (TGF24) conference took place from December 2nd to 5th, 2024, in the beautiful city of Lyon, France. Held at the historic Palais Hirsch and the equally magnificent Palais de la Bourse, the conference offered an inspiring setting along the Rhône River.

Since its inception in 1995, TGF has been a biennial event that brings together a diverse, interdisciplinary audience, including experts in physics, computer science, engineering, and fields such as pedestrian dynamics, granular flows, collective animal behavior, and urban mobility. This year’s conference continued the tradition of fostering collaboration and innovation by presenting the latest developments and ideas in these areas.

The scope of TGF covered a wide range of topics, including:

• Internet traffic and cyber systems,
• Pedestrian and evacuation dynamics,
• Urban Mobility,
• Trafic,
• Collective animal behavior,
• Swarm behavior, and
• Collective dynamics of biological systems.

Researchers from across the globe—spanning the USA, UK, Europe, Australia, New Zealand, Japan, China, India, and more—gathered to share their work and form new collaborations, which were facilitated by the smooth organization offering plenty of time for discussions between the partecipants. A particular highlight was the keynote by Andreas Schadschneider, who delivered a retrospective on nearly 30 years of TGF, celebrating its role in connecting scientists across disciplines and continents. Andreas explained how the conference started from a small group of physicists in Germany interested in traffic from a physical perspective and evolved into the global community studying a variety of subjects as it is today.

Another memorable presentation was by Ernesto Altshuler, whose talk, From Vortices to People: An Experimental Approach to Traffic, captivated the audience. Ernesto showed, through beautiful videos and funny anecdotes, how systems of different sizes show properties related to traffic systems and concluded his presentation showing some puzzling experiments on collective motion of people.

The conference also featured impactful contributions from attendees. For instance, Paul Geoerg and his co-authors presented their research on Mapping Crowd Safety Risks at a Global Scale, which introduced a meticulously curated database of 1,780 crowd-related events from 2000 to 2025. This database tracks incidents such as crowd crushes, terror attacks, and cancellations due to extreme weather, providing valuable insights for safety planning and risk assessment.

During the conference there was also the opportunity to showcase various software that have been created to help researchers working in the community. For instance, Peter Thompson presented a tool intended to visualize results from simulation or experiment in 3D to help gaining a more multi-facet inside into collected data. Ahmed Alia presented a comparison of Deep Learning-based Computer Vision tools used to track people’s heads in videos, a kind of software that is increasingly used by a variety of researchers to collect data on crowds.

In her invited talk Marta Gonzalez discussed traffic from a macroscopic perspective focusing on mobility patterns of people through data collected on mobile phones. Marta provided an overview of her impressive career presenting a number of graphs in videos in an informative way. On a smaller scale Xiaolu Jia presented a method to obtain origin-destination data of people moving inside a train station in Tokyo (Japan).

The conference also included a large number of presentations on pedestrian dynamics, vehicular traffic, collective animal behavior, network theory, and also some touching aspects closer to psychology.

Impressions and Atmosphere

TGF is renowned not only for its academic depth but also for its welcoming and collaborative environment. The informal atmosphere encourages open dialogue, making it easy for participants to engage in meaningful discussions regardless of their gender, nationality, or professional position. First-time attendees often remark on the strong sense of community and the openness to new ideas. Although TGF is held biannually, some participants also meed during the PED conference sharing some of the topics but specifically focused on pedestrian traffic.

This inclusivity has been a hallmark of TGF, thanks to the efforts of long-standing contributors like Andreas Schadschneider and Armin Seyfried, who have nurtured this culture over the years. Once again, the conference attracted a wide range of scientists from around the world, with a remarkable balance of ages and genders. Such diversity and openness ensure that the value of the content takes precedence over status.

Although the famous festival of lights was not part of the official program of the conference, many participants took the chance to enjoy the light show in a crowded scene. Probably given the crowd researchers in the conference a more realistic feeling for high densities.

Looking Ahead

As the conference came to a close, the steering committee announced that the next edition, TGF26, will be hosted by Nikolai Bode at Bristol University. With its strong foundation of inclusivity and innovation, TGF is set to continue thriving as a platform for cutting-edge research and collaboration. TGF26 is planning to continue the multidisciplinary tradition of TGF and will further extent its coverage to include also robotics, which is increasigly playing an important role in traffic through automated vehicles and swarm robotics. Of course, content from more “classical” topics typical of the past editions of TGF will be also welcome.

By: Ahmed Alia, Thomas Chatagnon, Claudio Feliciani

Edited by: Mohcine Chraibi