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Lane-free Artificial-Fluid Environment for Vehicular Traffic

Periodic Reporting for period 2 - TrafficFluid (Lane-free Artificial-Fluid Environment for Vehicular Traffic)

Reporting period: 2021-06-01 to 2022-11-30

Road traffic congestion is a serious threat for the economic and social life of modern societies as well as for the environment, which calls for drastic solutions. To efficiently address road capacity, traffic safety, fuel consumption and environmental problems, the TrafficFluid project puts forward a novel paradigm for vehicular traffic in the era of connected and automated vehicles (CAVs), which is based on two combined principles.
• The first principle is lane-free traffic, which: renders the driving task for CAVs smoother and safer, as risky lane-changing manoeuvres become obsolete; increases the static and dynamic capacity of the roadway due to increased lateral road occupancy; and mitigates congestion-triggering manoeuvres.
• The second principle is the nudge effect, whereby vehicles may be "pushing" (from a distance, using sensors or communication) other vehicles in front of them. This allows for CAV traffic to be freed from the restriction of human driving to be influenced only by downstream vehicles. The nudge effect is found to improve traffic flow capacity and stability.

TrafficFluid combines lane-free traffic with vehicle nudging to provide, for the first time since the automobile invention, the possibility to design (rather than merely describe or model) the traffic flow characteristics in an optimal way, i.e. to engineer the future CAV traffic flow as an efficient artificial fluid. To this end, the project develops the necessary vehicle movement strategies for various motorway and urban road infrastructures, along with microscopic simulators, macroscopic modelling of the emerging traffic flow and diverse traffic management actions.

TrafficFluid faces the challenge of designing a new traffic system from scratch; however, the project is triggering a new avenue of related international innovative research developments and testbeds that pave the way towards a new efficient traffic system in the era of CAVs.
TrafficFluid comprises four interconnected Work Packages (WP):
a) Vehicle Movement Design (WP1) addresses 2-D vehicle movement design so as to guarantee a number of significant properties regarding safety, fuel consumption, passenger convenience and efficiency.
b) Modelling and Simulation (WP2) develops a microscopic simulator as well as macroscopic traffic flow models that allow for proper reflection and assessment of the designed vehicle movement and emerging traffic features.
c) Extensions and Improvements (WP3) refers to three distinct levels: vehicle level, traffic level and infrastructure level; offering additional, e.g. traffic-dependent features and options, including traffic control measures for the new traffic paradigm.
d) Dissemination (WP4) includes a multitude of actions aiming at promoting the ground-breaking character of TrafficFluid research.

Please visit our website www.trafficfluid.tuc.gr for more information. Among others, the website includes several videos illustrating published research results.
Progress up to this mid-term activity report has been largely according to plan, with some delays attributed to delayed new personnel hiring and starting due to the covid-19 pandemic.

Within WP1, we are working in parallel on four methodological avenues to derive efficient vehicle movement strategies, namely using ad-hoc, machine learning (reinforcement learning), optimal control and nonlinear feedback control approaches. Within WP2, there are good and ongoing advancements regarding both the microscopic simulator and the macroscopic model developments. Finally, within WP3, excellent progress has been achieved, mainly with an innovative and very promising traffic management method, which is internal boundary control (IBC).

All mentioned progress is reflected in corresponding conference and journal papers. Dissemination activities include:
a) Creation and continuous enrichment of the project’s website www.trafficfluid.tuc.gr. Its visiting statistics are: 34,833 times by 6,897 different visitors; 79% from Europe, 11% from North America, 9% from Asia and 1% from the rest of the world.
b) Articles (in the most renowned journals and conferences in the concerned areas): 11 journal, 22 conference articles.
c) 14 research-related video groups to illustrate research results.
d) Beyond the conference paper presentations, the PI and TrafficFluid members delivered 41 invited presentations at research organisations and scientific events in 13 countries, among them several keynote presentations at conferences.
e) Organisation of 3 seminars of external scientists.
f) Organization of Special Sessions at conferences and Special Issues at journals.
g) Hosting of 3 visitors from Germany, USA and France, respectively, over 2-4 months each.
h) Several media reports and interviews.

Finally, collaboration with two research groups, one from Technical University of Munich, Germany; and another from Zhejiang University, China, was agreed and has been ongoing on issues related to the TrafficFluid paradigm, which are not kernel issues for our project.
Given the profoundly innovative scope of the project, virtually all developments and achievements are addressing “new land”, thereby extending the state-of-the-art in automated vehicle movement design, CAV macroscopic traffic flow modelling, traffic management and more. More specifically:
1. Vehicle Movement Design: Beyond first basic investigations applying to a "pipeline" or circular road, additional critical circumstances, such as efficient merging, diverging and weaving policies, as well as driving on complex roundabouts are addressed.
2. Modelling and Simulation: The microscopic simulator TrafficFluid-Sim has been developed on the basis of the open-source tool SUMO and is continuously extended to cover emerging needs in the project. In addition, activities addressing theoretical development of macroscopic traffic flow models under the TrafficFluid concept, as well as model calibration and validation by use of TrafficFluid-Sim data are in full progress.
3. Extensions and Improvements: At vehicle level, the presence of manually driven vehicles or 2-D platooning vehicles or emergency vehicles are being investigated. At traffic level, based on experience with conventional traffic control, we design traffic control measures to mitigate congestion, such as ramp metering, mainstream traffic flow control and, as a particular opportunity enabled by the TrafficFluid concept, internal boundary control (IBC). Our investigations show that particularly the novel traffic control measure IBC leads to unprecedented increase of road utilization. At the infrastructure level, additional infrastructure types and traffic scenarios, such as arterials, signalised urban junctions, roundabouts, are considered. In particular, we are addressing, as an interesting case study and challenge, the lane-free movement of automated vehicles on a very complex lane-free roundabout, the Charles-de-Gaulle Place roundabout in Paris, France.
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