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Lane-free Artificial-Fluid Environment for Vehicular Traffic

Periodic Reporting for period 1 - TrafficFluid (Lane-free Artificial-Fluid Environment for Vehicular Traffic)

Reporting period: 2019-12-01 to 2021-05-31

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 and radical solutions. To efficiently address road capacity problems, the TrafficFluid project puts forward an utterly original idea that leads to a novel paradigm for vehicular traffic in the era of connected and automated vehicles (CAVs) and 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 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 traffic flow to be freed from the anisotropy restriction, which stems from the fact that human driving is influenced only by downstream vehicles. The nudge effect may be implemented in various possible ways, so as to maximize the traffic flow efficiency, subject to safety and convenience constraints.

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 will develop and deliver the necessary vehicle movement strategies for various motorway and urban road infrastructures, along with microscopic and macroscopic simulators and traffic management actions.

TrafficFluid risk stems from the immense challenge of designing a new traffic system from scratch; however, we expect that the project will trigger a whole new path of international innovative research developments and testbeds that would 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, passenger convenience and efficiency;
b) Modelling and Simulation (WP2) develops appropriate models at the microscopic and macroscopic levels, that allow for a proper reflection and assessment of the designed vehicle movement and resulting traffic features;
c) Extensions and Improvements (WP3) refers to 3 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.
Progress within this first reporting period has been largely according to plan. 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 is good advancement regarding both the microscopic simulator and the macroscopic model development. Finally, within WP3, excellent progress has been achieved, mainly with an important and very promising traffic management method, which is internal boundary control. All mentioned progress is reflected in corresponding published/submitted conference and journal papers. Progress has been closely monitored via 14 monthly Progress Meetings.

Strong dissemination activities were conducted, including: (a) Creation and continuous enrichment of the project’s website; (b) 7 journal articles (3 accepted) and 9 conference articles (8 accepted); (c) 8 research related video groups; (d) Some 10 invited presentations at research organisations and some 15 invited presentations at events, among them several keynotes at conferences; (e) 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. The collaboration concerns issues related to the TrafficFluid paradigm, which are not kernel issues for our project.
The TrafficFluid concept concerns future traffic flow on motorways, highways, arterials and, potentially, also urban roads. TrafficFluid combines lane-free traffic with vehicle nudging to provide, for the first time since the automobile invention, the possibility to design 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, a number of activities have been planned as follows:

1. Vehicle Movement Design: This is a cornerstone of TrafficFluid developments, because all intrinsic features of the novel traffic flow paradigm stem from this level. 2-D vehicle movement is being designed to guarantee safety, passenger convenience, as well as stability and the generalised notion of string stability. Beyond a first basic approach applying to a "pipeline" or circular road, a number of additional critical issues, such as efficient merging, diverging and weaving policies, are addressed.

2. Modelling and Simulation: In order to capture, visualise, analyse, quantify and assess different choices, architectures and parametrisations with respect to vehicle movement design, it is indispensable to dispose a microscopic simulator. In addition, for various levels of qualitative and quantitative assessment as well as for traffic control strategy design, it is also useful to develop macroscopic models which reflect more directly the traffic characteristics at the fluid level.

3. Extensions and Improvements: A third group of TrafficFluid activities is the development, investigation and assessment of a number of possible extensions and additional improvements at three levels:
a. At vehicle level, several vehicle movement elements are introduced or modified, some of them in dependence of the traffic conditions prevailing around the vehicle, aiming at farther improving the safety, passenger convenience and efficiency properties of traffic. Among others, the presence of manually driven vehicles or platooning vehicles or emergency vehicles will be investigated.
b. At traffic level, we expect that the current road capacity will rise sensibly with TrafficFluid, but there is always an upper limit, hence there is the possibility of traffic congestion, if the demand increases accordingly. Based on experience with conventional traffic control, we are addressing, within the utterly new TrafficFluid environment, the consequences of traffic congestion, and design, partly in collaboration with other research groups, possible traffic control measures to mitigate it, such as ramp metering, variable speed limits, mainstream traffic flow control and, as a particular opportunity enabled by the TrafficFluid concept, internal boundary control.
c. At the infrastructure level: Although the bulk of the project investigations address motorway and highway infrastructures, we are also considering, partly in collaboration with other research groups, additional infrastructure types and traffic scenarios, such as signalised arterials, signalised urban junctions, roundabouts and other options.
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