Ifsttar - Salles B017-B020 - 14 - 20 Boulevard Newton - Marne-la-Vallée, France.
|| Guilhem Mariotte, Ifsttar/Cosys/Licit. Slides
|| Titre. Modeling traffic flow at the network scale with multi-reservoir systems using the MFD.
|| Résumé. Over the past decade, the Macroscopic Fundamental Diagram (MFD), relating the mean flow vs the mean density
of a given urban area, has appeared to be a powerful tool to describe traffic states at the network level with few implementation and
computational efforts. Many studies (e.g. Knoop & Hoogendoorn, 2014, Yildirimoglu & Geroliminis, 2014, Yildirimoglu et al., 2015,
Haddad, 2015) have notably used MFD-based traffic simulators for several applications, like traffic state estimation, perimeter
control or assessing routing strategies at a large scale. Their modeling approaches take advantage of the multi-reservoir
representation of a city, where the dynamics of each urban subregion is described by the single reservoir model of Daganzo (2007).
This framework, also referred as the "accumulation-based model", assumes that the reservoir outflow is proportional to the circulating
flow inside the zone. However, while being acceptable in slow-varying conditions, this hypothesis may be too restrictive when the
demand evolves too fast as shown by Mariotte et al. (2017). An idea, initially proposed in Arnott (2013), has been exploited in
Daganzo & Lehe (2015) and then Lamotte & Geroliminis (2016) to design a "trip-based" formulation of the MFD model. This approach
considers that all users travel at the same speed at a given time, and exit the zone once they have completed their individually
assigned trip length. Although both approaches have already been used many times in various studies, challenging issues about
congestion propagation between the reservoirs have received little attention in the literature. This presentation intends to shed
some light on these questions, together with a short overview on these models. Case studies of reservoirs crossed by routes with
different lengths will be presented.
| || |
|| Cyril Nguyen Van Phu, Ifsttar/Cosys/Grettia. Slides
|| Titre. A vehicle-to-infrastructure communication based algorithm for urban traffic control.
|| Résumé. We present a new algorithm for urban traffic light control with mixed traffic (communicating and non communicating vehicles)
and mixed infrastructure (equipped and unequipped junctions). We call equipped junction here a junction with a traffic light signal (TLS) controlled
by a road side unit (RSU). On such a junction, the RSU manifests its connectedness to equipped vehicles by broadcasting its communication address and
geographical coordinates. The RSU builds a map of connected vehicles approaching and leaving the junction. The algorithm allows the RSU to select a
traffic phase, based on the built map. The selected traffic phase is applied by the TLS; and both equipped and unequipped vehicles must respect it.
The traffic management is in feedback on the traffic demand of communicating vehicles. We simulated the vehicular traffic as well as the communications.
The two simulations are combined in a closed loop with visualization and monitoring interfaces. Several indicators on vehicular traffic (mean travel
time, ended vehicles) and IEEE 802.11p communication performances (end-to-end delay, output rate, throughput, and packet error delivery ratio) are
derived and illustrated in three dimension maps. We then extended the traffic control to a urban road network where we also varied the number of
equipped junctions. Other indicators are shown for road traffic in the case of a road network control where high gains are experienced in the
| || |
|| Pause Café.
| || |
|| Kwami Sossoe, Ifsttar/Cosys/Grettia. Slides
|| Titre. Reactive Dynamic Assignment in Discrete-continuous Large-scale Transport networks.
|| Résumé. In the field of traffic flow modeling of large-scale surface networks, a bi-dimensional traffic flow modeling framework emerged.
It is a family model developed at a greater scale. The theory of traffic flow at this scale of modeling is a high-level of aggregation of road sections
and road intersections, in zones of two dimensions. The corresponding network domain of such surface network is approached as a continuous network that
comprises infinite secondary roads. A specific dynamic network loading is proposed to compute vehicles flow on such continuous network, while a reactive
assignment scheme is designed for dynamic traffic assignment. A Dijkstra-based algorithm is used to find time dependent shortest paths over large networks
in this context, where instantaneous travel times are considered instead. Since urban network may comprise major roads like highways, a coupling of GSOM
macroscopic flow model (applied to discrete network) with the bi-dimensional flow model (applied to the continuous network) is discussed. The new proposed
transport model has the capability of reducing significantly computational complexity. Moreover, the model is suitable for networks with few traffic data sources.