Panneau de signalisation routière

Résumé

thumb|Panneau (États-Unis) signalant le passage d'enfants et indiquant une limitation de vitesse thumb|Panneau de signalisation bilingue indiquant l'entrée d'une agglomération en Italie. thumb|Panneau (Débuts de la signalisation routière) : les panneaux du Touring club de France en 1904. Les panneaux de signalisation routière sont des éléments de la signalisation routière. Ils désignent à la fois le dispositif sur lequel est implanté un signal routier et le signal proprement dit. Placés sur le côté des routes, ils ont pour fonction

de rendre plus sûre la circulation routière en informant les usagers d’éventuels dangers qu’ils peuvent rencontrer ;
de faciliter cette circulation, en indiquant par exemple les directions à suivre ;
d'indiquer ou de rappeler diverses prescriptions particulières de police ;
de donner des informations relatives à l'usage de la route.

Histoire La signalisation routière est aussi vieille que les routes. Les premiers signes furent ceux donn

Source officielle

https://fr.wikipedia.org/wiki/Panneau_de_signalisation_routi%C3%A8re

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Traffic Locality as an Opportunity in the Data Center

Jonas Fietz

In large scale data centers, network infrastructure is becoming a major cost component; as a result, operators are trying to reduce expenses, and in particular lower the amount of hardware needed to achieve their performance goals (or to improve the performance achieved for a given amount of hardware). In this thesis, we explore the use of locality in the data center to meet these demands. In particular, we leverage locality in two different projects: (1) VNToR, which moves network virtualization from the server to the top-of-rack (ToR) switch, thereby reducing the server hardware needed to achieve a certain performance, and (2) Criss-Cross, which makes the network topology reconfigurable, thereby reducing the network hardware needed to switch typical data center workloads with a given level of performance. VNToR exploits the locality of traffic flows as well as their long-tailed behavior in the design of a virtual flow table, which extends the hardware flow table of off-the-shelf top-of-rack switches. VNToR uses this virtual flow table in a hybrid data plane that consists of both a hardware as well as a software data plane. This way it can (1) store tens or even hundreds of thousands of access rules, (2) adapt to traffic-pattern changes, typically in less than one millisecond, and (3) uses only commodity switching hardware with a minimal amount of data path memory (4)~without compromising latency or throughput. Criss-Cross is a hierarchical, reconfigurable topology for large-scale data centers. The locality in rack-level flows allows Criss-Cross to adjust its topology to the current traffic patterns. We show that Criss-Cross preserves many of the advantages of Clos topologies: (1) it maintains their hierarchy, (2) the simple routing algorithms, (3) their regular layout of connections for simple physical deployability, and (4) the compatibility to existing management approaches. We demonstrate that for a group-based communication pattern, Criss-Cross improves the average flow completion time by 5.5x and the 99th percentile by 6.3x. For a purely random point-to-point traffic pattern, it improves the flow completion time by 2.2x on average and 3x at the 99th percentile.

EPFL2019

Chargement

This research is the result of four years of practical and scientific investigation of the phenomenon of traffic evaporation, which was considered and then demonstrated to be the opposite of traffic induction. It has anchored, in practice and in time, an orphaned and scarcely documented topic in literature which mobility planners are facing. Our research was conducted with one foot firmly grounded in the practice of mobility engineering and the other in the urban sociology of mobility behaviour. Immersed in the first field as a "project engineer" on various projects, I was able to investigate a great number of case studies and enrich the thesis with the questions of experts and commissioners. In order to answer these questions, beyond the quantitative and measurable aspects that account for the engineer's daily bread, the qualitative methods of urban sociology were mobilised to decipher the rationales for action of these individuals that make up traffic flows.This singular approach revealed the number and diversity of factors that are at play in the mechanism of traffic evaporation. These include motility, the mental cost of learning, the anchoring of modal habits and the value rationale of each individual. At the crossroads of the three research foci, which are usually treated separately and which we have combined in our case studies, i.e. the temporality of disruption, the (re)actions of the authorities and the weight of (multi)modal habits, we have been able to observe orders of magnitude beyond traffic evaporation. The results show, first of all, that traffic evaporation is achievable over the long-term of urban planning, because the time of mobility habits and learning of usage is also long, although it seems to accelerate once learning is triggered. Moreover, our results show that traffic volumes which we thought would always increase in the past can be controlled. This legitimate confidence in the reversibility of traffic induction draws attention to levers that are now, in turn, perhaps being underestimated in mobility planning.Secondly, the study of urban construction sites has shown that the keys to understanding the reactions of the traffic flow lie in the varied profiles of the individuals who make it up. Knowing their rationales for action, it is possible to assess which behavioural changes will be temporary and which will be lasting, and thus to steer them if desired.Finally, we have revealed that, in the face of the unforeseen, the activation of motility levers is strong and prompt, with the aim of overcoming personal barriers to change. In these cases, the behaviours adopted seem to last beyond the duration of the disruption.Thus, traffic evaporation appears to be much more than a new variable to be considered in mobility analyses and planning. It calls into question the logic that has driven travel planning in the automobile era.

EPFL2022

Chargement

AGIR - A decision support tool for Geneva ring-road traffic management during important events

Emmanuel Bert

Geneva is a city used to organise international events like for example the International Motor Show which takes place every year. Most of these events are hold on the Palexpo area, a group of buildings situated near the Geneva airport. Both places are closely connected to the city ring highway. Traffic generated by this type of events obviously implies a totally different demand distribution shape compared to usual days. In addition, traffic volumes recorded during the event peak hours, (usually observed around the opening and closing hours), can reach up to the double of the ones ordinarily experienced. Given that the road network has not been design to handle this type of demand, important congestions are consequently observed during event periods implying important accidents risk, parking lot saturation and an overuse of the local network provoking annoyances for residents. In order to minimize these problems, the Geneva Transport Office asked Arx iT and CITEC (both local consultancy companies) to develop a method for supporting traffic management on the ring road. The basic concept is to implement in the Geneva highway traffic centre an on- line traffic data analysis tool which is able to, depending on the traffic situation (data coming from loop detectors and cameras) and parking lots occupancy, suggest a set of recommendations to be provided to road users through variable message signs. The whole process mainly relies on comparisons between the current network status and historical situations already observed during past events. For each of these situations correspond a traveller information scenario which has been designed based on empirical experiences. Although this tool has been offering reasonably good results for three years, situations without clear correspondence with past conditions are still frequently observed and the lack of experience on this particular cases lead sometimes to erroneous information scenario selection. Of course, facing these new situations allows traffic operators to increase their human knowledge, on which mainly relies the current AGIR process. Nevertheless, need for more systematic analysis process has been clearly identified. Reproducing various traffic situations without having to wait them to occur in reality is one of the major purposes of using traffic simulation tools in transportation studies. Thus, EPFL (Swiss federal Institute of Technology) has been in charge to assess the current AGIR system performances and to improve the knowledge data base through artificial experiments using a microsimulation model of the Geneva ring highway and part of the local network. For this task, EPFL has been helped by TSS, the company developing AIMSUN NG, the traffic simulator used for this analysis. The use of microsimulation offered the possibility of dynamically study the network’s traffic reaction to the information provided to simulated drivers by the AGIR system. This reaction implying new traffic data outputs, which are used as input for the AGIR process, the time dependent interaction between traffic situation and information system is fully captured. As simulation models offer statistical traffic outputs for each network element, global performance indexes could be computed offering a more realistic assessment of situation that only relying on traffic detection data. This complementary approach has been shown to be particularly efficient to improve current process and offer better answers to non frequent situations. Currently done off- line, possible integration of the simulation tool for on- line decision process is discussed for the future.

2006

Chargement

AGIR - A decision support tool for Geneva ring-road traffic management during important events

Emmanuel Bert

2006

EPFL2022

Traffic Locality as an Opportunity in the Data Center

Jonas Fietz

EPFL2019