Managing and directing the traffic of the future

Jun.- Prof. Dr. Antoine Tordeux on the complex system of road traffic

When the four-lane motorway on the A3 between Solingen and Cologne was recently narrowed down to one lane again, and the travel time was extended from 45 minutes to a full three hours, young professor Dr. Antoine Tordeux was able to realise once again how important his research, on optimizing traffic flows, is. Since 2018, the 37-year-old Frenchman has been working in the Department of Traffic Safety/Reliability in Safety Engineering at the University of Wuppertal. He mainly focuses on the Traffic Flow Theory. "The Traffic Flow Theory is a multidisciplinary scientific theory with which engineers, mathematicians, physicists, computer scientists, electrical engineers, sociologists, psychologists, etc. interact to understand traffic," he says, because there are many paradoxes that science has not yet understood. This theory is therefore mainly applied in the development of traffic simulation tools to test and evaluate transport networks, road infrastructures and management strategies.

Nonlinear phenomena

"Simple experiments at a narrow place, where the road narrows down from two lanes to one, show that drivers driving 100 km/h are forced to slow down to 10 km/h. The flow is halved, the speed is reduced by a factor of 10, which is a typical facet of traffic that makes it complex. In science we talk about non-linear phenomena". These phenomena describe situations that are not clearly predictable, but can at least be estimated, and are being investigated using new methods. In the case of road narrowing, the capacity of the traffic network is thus immediately exceeded and accumulation occurs, to put it simply, Tordeux says. "This is the principle of the hourglass".
Experiments also show that congestion is not necessarily caused by narrowed roads or construction sites at all times. "A driver has to regulate his speed distance individually in order to avoid collisions and maintain safety distances," explains the scientist. Experiments show that this behavior causes disruptions and makes it possible to create traffic congestions even without constrictions by means of so-called stop-and-go waves.

Avoiding traffic congestions through automated driving?

Therefore, his research also focuses on investigations to determine the vehicle speed by means of automated driving. "Automated driving can reduce reaction times and thus improve performance," he explains. This is done by means of so-called platooning, a system currently under development for road traffic. Here, a technical control system allows several vehicles to follow each other at a small distance without compromising traffic safety. "We can thus achieve an improved, more optimal use of the transport networks." However, this does not necessarily mean reducing traffic congestions. Tordeux refers to the Downs-Thomson paradox, which states that improvements in the road network can increase congestion if the improvements affect public transport or if they shift investment, which in turn leads to lower investment in the public transport system. "But automated driving can increase user safety," explains Tordeux, "because more than 90% of accidents are caused by human error!" It also protects the environment, reduces road traffic costs, allows people without a driver's license to participate and enables other activities while driving.

40% of pollutant emissions are non-exhaust emissions

Pollutant emissions also play a major role in the optimization of traffic flows. Here, the layman immediately thinks of exhaust gases. Hardly anyone knows that 40% of all pollutants are caused by non-exhaust emissions. "This is mainly the wearout of tires and brake pads. They contribute to the fine dust pollution of cities" says Tordeux. "The control of collective stop-and-go waves, e.g. by means of stable, automated distance and speed control systems or optimal stability control can play a role here". He explains that it is difficult to make a comprehensive assessment of pollutant emissions, since this requires estimating the total emissions from traffic, including the life cycle of each individual vehicle. Even the future-oriented electric car has its pitfalls in this respect. "Electric cars, for example, even if they do not produce any exhaust emissions, only begin to be more ecological than combustion engines when they are used for between 80,000 and 120,000 kilometers. And the production of the battery is still a very environmentally harmful process."

Optimal traffic light control at Robert-Daum-Platz

The scientist has the traffic in the Bergisch Land always in mind. His junior endowed professorship is funded for a period of six years by the Eugen Ottoutz Foundation from Hilden. "As part of the Bergisch.Smart.Mobility project (www.bergischsmartmobility.de), we are trying to improve some of the intersections in the Bergisch Land, e.g. at Robert-Daum-Platz in Wuppertal, or on Bonner Strasse/Langhansstrasse in Solingen, by optimizing traffic light control and road infrastructure," explains Tordeux. Above all, it is important to encourage the choice of transport mode of road users, by developing a suitable and safe infrastructure. With regard to a car, he says: "Remember that the average number of people per vehicle is only 1.2 and that traffic, seeking parking, can account for up to 30% of traffic in inner city areas". The situation in Wuppertal is also more complex, he states. Even cycling in hilly urban areas restricts many users. Tordeux therefore considers multimodal solutions as a sensible option. This includes i.e. the possibility for road users to have at least two transport alternatives available for their individual mobility needs.

A healthy mix is needed to manage and direct the traffic of the future. There is still a long way to go before we can move away from fossil-fuel-powered cars to bicycle, electric and public transport. The work of the mathematician Antoine Tordeux has played a major role in this.

Uwe Blass (Interview on October 10, 2020)

Antoine Tordeux studied Mathematics at the Université Paris-Est. There, he received his doctorate in 2010. He analysed time-continuous processes for modeling road traffic. Until 2012, he worked as a research assistant at the Université Paris-Est. Afterwards he moved to Wuppertal and worked with Prof. Armin Seyfried at the Teaching and Research Department Computer Simulation for Fire Protection and Pedestrians and at the Institute for Advanced Simulation, Selection Civil Safety at the Research Center Jülich. In 2018, he took over the junior professorship for Traffic Safety/Reliability in the School of Mechanical Engineering and Safety Engineering, funded by the Eugen Otto Butz Foundation of Hilden.