Clélia Lopez

Bio: Clélia Lopez is an academic researcher from University of Lyon. The author has contributed to research in topics: Traffic simulation & Truck. The author has an hindex of 5, co-authored 7 publications receiving 275 citations. Previous affiliations of Clélia Lopez include IFSTTAR.

Revealing the day-to-day regularity of urban congestion patterns with 3D speed maps.

Abstract: In this paper, we investigate the day-to-day regularity of urban congestion patterns. We first partition link speed data every 10 min into 3D clusters that propose a parsimonious sketch of the congestion pulse. We then gather days with similar patterns and use consensus clustering methods to produce a unique global pattern that fits multiple days, uncovering the day-to-day regularity. We show that the network of Amsterdam over 35 days can be synthesized into only 4 consensual 3D speed maps with 9 clusters. This paves the way for a cutting-edge systematic method for travel time predictions in cities. By matching the current observation to historical consensual 3D speed maps, we design an efficient real-time method that successfully predicts 84% trips travel times with an error margin below 25%. The new concept of consensual 3D speed maps allows us to extract the essence out of large amounts of link speed observations and as a result reveals a global and previously mostly hidden picture of traffic dynamics at the whole city scale, which may be more regular and predictable than expected.

Spatiotemporal Partitioning of Transportation Network Using Travel Time Data

Abstract: Nowadays, the deployment of sensing technology permits to collect massive 1 spatio-temporal data in urban cities. These data can provide comprehensive traffic state conditions for an urban network and for a particular day. However, they are often too numerous and too detailed to be of direct use, particularly for applications like delivery tour planning, trip advisors and dynamic route guidance. A rough estimation of travel times and their variability may be sufficient if the information is available at the full city scale. The concept of spatio-temporal speed cluster map is a promising avenue for these applications.

Modélisation dynamique du trafic et transport de marchandises en ville : vers une approche combinée

Abstract: Cette these propose une modelisation des interactions entre le Transport de Marchandises en Ville (TMV) et la dynamique du trafic. Ces deux composantes, pourtant imbriquees, ne sont que tres rarement etudiees simultanement. Plus precisement, cette these investigue les impacts du TMV sur les etats de trafic ; et inversement, les impacts des etats de trafic sur le TMV. Les recherches s’articulent autour de deux axes : le TMV a l’echelle (i) de la livraison et (ii) de la tournee de livraison, et la dynamique du trafic a l’echelle (iii) d’un jour et (iv) d’un catalogue de jours. (i) Le TMV realise par des vehicules routiers peut engendrer des formes de congestion, et par consequent des nuisances sonores et atmospheriques. Neanmoins, il s’agit d’un « mal necessaire » car le transport de ces marchandises est essentiel pour l’economie des villes. Une pratique courante est la livraison en double file. Ces « stationnements sauvages » reduisent l’ecoulement des vehicules dans le reseau de transport. Une etude de sensibilite quantitative en simulation microscopique met en lumiere une degradation significative des etats de trafic sur un boulevard urbain a partir d’un faible nombre de stationnements en double file. Ces phenomenes locaux et temporaires semblent essentiels a integrer dans les simulations du trafic afin d’etudier au mieux les performances globales du systeme de transport. (ii) Les tournees de livraison planifiees peuvent etre ameliorees par l’integration des conditions de circulation. Les algorithmes existants d’optimisation de tournees se basent sur une certaine qualite et quantite de donnees. Nous investiguons l’influence de plusieurs niveaux de granularite d’information du trafic sur l’ordonnancement optimale des tournees. De plus, nous comparons les temps de parcours estimes par les algorithmes, et les temps de parcours effectifs estimes a l’aide d’une simulation microscopique. Les etats de trafic attendus peuvent etre sujets a quelques variations. Nous proposons une methodologie de generation de tournees integrant de l’incertitude dans la dynamique du trafic. (iii) A l’echelle de la ville, les etats de trafic sont naturellement variables, que ce soit dans l’espace ou au cours du temps. Le partitionnement permet de decouper un reseau de transport en zones homogenes. Une zone est definie par un ensemble de liens connectes ayant des conditions de circulation similaires. Nous proposons une approche spatio-temporelle definissant des zones en 3 Dimensions (3D). L’idee est de resumer la majeure partie de la dynamique du trafic d’une ville en utilisant peu d’information : la vitesse moyenne par zone spatio-temporelle. Deux familles de methodes de clustering fondamentalement differentes sont comparees et evaluees. Le cas d’etude est le reseau d’Amsterdam avec des donnees reelles. (iv) D’un jour a l’autre, la dynamique du trafic peut etre similaire. Nous proposons une methodologie regroupant les jours par leurs motifs de congestion. L’existence d’une regularite dans les motifs journaliers est introduite par la notion de jour-type. Un jour-type est le jour de reference d’un groupe de jours. Nous validons notre modele en comparant les temps de parcours effectifs et les temps de parcours estimes par les jours-types. Diverses applications peuvent etre raffinees a partir de quelques jours-types, comme l’assistance routiere et la generation de tournees.

Microscopic Simulation of Cruising for Parking of Trucks as a Measure to Manage Freight Loading Zone

Abstract: This paper investigated economic truck parking behavior to implement comprehensive Freight Loading Zone (FLZ) policies. We assumed that the delivery trucks can only park on FLZ. The proposed contribution is to quantify the cruising for parking time of trucks. We used a microscopic traffic simulation based on a Manhattan network and the real network of Lyon (France). This paper explored the relationship between the searching time, the parking probabilities and the region’s parking density. Based on research results, an application to last mile cost function is proposed.

Evaluation of the Performance of an Urban Freight System Using a Multi-use-Lane Arterial

Abstract: Even if urban logistic has been extensively investigated in the literature, its effects on traffic flow dynamics remain mostly unknown. This paper aims to introduce a general methodology to anticipate and evaluate the impacts of urban logistics and associated city logistics actions on the global performance of a transportation network. This first study focuses on urban arterial level and investigates the possible benefits of a multi use lane strategy deployment. Influence of such a solution in favor of urban freight activities must be carefully and deeply studied before implementation. To this end, the authors resort to a theoretical but realistic urban arterial to compare the deployment of a multi use lane strategy with the classical mixed lane case. The systematic and gene ral methodology proposed in the paper makes it possible to identify optimal domains of applications, Le. traffic conditions and urban freight characteristics, where a dedicated lane for deliveries may be efficient and simultaneously maintains a satisfactory global performance of the arterial.

Revealing the day-to-day regularity of urban congestion patterns with 3D speed maps.

Abstract: In this paper, we investigate the day-to-day regularity of urban congestion patterns. We first partition link speed data every 10 min into 3D clusters that propose a parsimonious sketch of the congestion pulse. We then gather days with similar patterns and use consensus clustering methods to produce a unique global pattern that fits multiple days, uncovering the day-to-day regularity. We show that the network of Amsterdam over 35 days can be synthesized into only 4 consensual 3D speed maps with 9 clusters. This paves the way for a cutting-edge systematic method for travel time predictions in cities. By matching the current observation to historical consensual 3D speed maps, we design an efficient real-time method that successfully predicts 84% trips travel times with an error margin below 25%. The new concept of consensual 3D speed maps allows us to extract the essence out of large amounts of link speed observations and as a result reveals a global and previously mostly hidden picture of traffic dynamics at the whole city scale, which may be more regular and predictable than expected.

City logistics : network modelling and intelligent transport systems

Abstract: Chapter headings: Introduction. Modelling city logistics. City logistics with ITS. Demand and supply models. Impact models. Vehicle routing and scheduling. Vehicle routing and scheduling with ITS. Location of logistics terminals. Future perspectives. References. Index.

On the new era of urban traffic monitoring with massive drone data: The pNEUMA large-scale field experiment

Abstract: The new era of sharing information and “big data” has raised our expectations to make mobility more predictable and controllable through a better utilization of data and existing resources. The realization of these opportunities requires going beyond the existing traditional ways of collecting traffic data that are based either on fixed-location sensors or GPS devices with low spatial coverage or penetration rates and significant measurement errors, especially in congested urban areas. Unmanned Aerial Systems (UAS) or simply “drones” have been proposed as a pioneering tool of the Intelligent Transportation Systems (ITS) infrastructure due to their unique characteristics, but various challenges have kept these efforts only at a small size. This paper describes the system architecture and preliminary results of a first-of-its-kind experiment, nicknamed pNEUMA, to create the most complete urban dataset to study congestion. A swarm of 10 drones hovering over the central business district of Athens over multiple days to record traffic streams in a congested area of a 1.3 km2 area with more than 100 km-lanes of road network, around 100 busy intersections (signalized or not), many bus stops and close to half a million trajectories. The aim of the experiment is to record traffic streams in a multi-modal congested environment over an urban setting using UAS that can allow the deep investigation of critical traffic phenomena. The pNEUMA experiment develops a prototype system that offers immense opportunities for researchers many of which are beyond the interests and expertise of the authors. This open science initiative creates a unique observatory of traffic congestion, a scale an-order-of-magnitude higher than what was available till now, that researchers from different disciplines around the globe can use to develop and test their own models.

Dynamic clustering and propagation of congestion in heterogeneously congested urban traffic networks

Abstract: The problem of clustering in urban traffic networks has been mainly studied in static framework by considering traffic conditions at a given time. Nevertheless, it is important to underline that traffic is a strongly time-variant process and it needs to be studied in the spatiotemporal dimension. Investigating the clustering problem over time in the dynamic domain is critical to better understand and reveal the hidden information during the process of congestion formation and dissolution. The primary motivation of the paper is to study the spatiotemporal relation of congested links, observing congestion propagation from a macroscopic perspective, and finally identifying critical pockets of congestion that can aid the design of peripheral control strategies. To achieve this, we first introduce a static clustering method to partition the heterogeneous network into homogeneous connected sub-regions. The proposed framework guarantees connectivity of the cluster in different steps, which eases the development of a dynamic framework. The proposed clustering approach has 3 steps; firstly, it obtains a set of homogeneous connected components in the network. Each component has a form of sequence which is built by sequentially adding neighboring links with similar level of congestion. Secondly, the major skeleton of clusters is obtained out of this feasible set by minimizing a heterogeneity index. Thirdly, a fine-tuning step is designed to complete the clustering task by assigning the unclustered links of the network to proper clusters while keeping the connectivity. The optimization problem in both second and third step is formulated as a mixed integer linear programming. The approach is also extended to capture spatiotemporal growth and formation of congestion. The dynamic clustering is based on an iterative and fast procedure that considers the spatiotemporal characteristics of congestion propagation and identifies the links with the highest degree of heterogeneity due to time dependent conditions and finally re-cluster them to guarantee connectivity and minimize heterogeneity. An implementation of the developed methodologies in a megacity based on more than 20,000 taxis with GPS highlights the quality of the method due to its fast computation and proper integration of physical properties of congestion.

Limits of predictability in human mobility

Abstract: A range of applications, from predicting the spread of human and electronic viruses to city planning and resource management in mobile communications, depend on our ability to foresee the whereabouts and mobility of individuals, raising a fundamental question: To what degree is human behavior predictable? Here we explore the limits of predictability in human dynamics by studying the mobility patterns of anonymized mobile phone users. By measuring the entropy of each individual's trajectory, we find a 93% potential predictability in user mobility across the whole user base. Despite the significant differences in the travel patterns, we find a remarkable lack of variability in predictability, which is largely independent of the distance users cover on a regular basis.