Haut PDF A global take on congestion in urban areas

A global take on congestion in urban areas

A global take on congestion in urban areas

190-198 avenue de France, FR-75013 Paris, France We analyze the congestion data collected by a GPS device company (TomTom) for almost 300 urban areas in the world. Using simple scaling arguments and data fitting we show that congestion during peak hours in large cities grows essentially as the square root of the population density. This result, at odds with previous publications showing that gasoline consumption decreases with density, confirms that density is indeed an important determinant of congestion, but also that we need urgently a better theoretical understanding of this phenomena. This incomplete view at the urban level leads thus to the idea that thinking about density by itself could be very misleading in congestion studies, and that it is probably more useful to focus on the spatial redistribution of activities and residences.
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Global Positioning in Urban Areas with 3-D Maps

Global Positioning in Urban Areas with 3-D Maps

Global Positioning in Urban Areas with 3-D Maps Vincent Drevelle and Philippe Bonnifait Abstract— A global positioning method based on a precise 3-D drivable area map and on GPS pseudorange measurements is presented. Map and GPS measurements are represented by geometric constraints, thus turning the localization problem into a constraint satisfaction problem whose solution is the confidence domain of position. Interval analysis is employed to solve the problem by using contractions and bisections of a prior position box. If more than 3 satellites are visible, the method is robust to wrong pseudorange measurements. The system is also able to compute multiple position hypotheses in the case of ambiguities. An experimental validation using real GPS pseudorange measurements and a precise 3-D map is reported to illustrate the performance of the method with real data in an urban area, with reduced satellite visibility. Confidence domains are consistent with the truth during the whole 1 km experiment, and a 6.5 m 95% accuracy is achieved with at least two satellites in view.
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Water partial privatization: access and quality consequences for urban areas in Senegal

Water partial privatization: access and quality consequences for urban areas in Senegal

Many governements in the developing world, usually pushed by the international donors, embarked in the 1990s on ambitious reforms of their urban water supply and sanitation ser- vices. These reforms have often included the delegation of utilities’ supervision to private operators, under various contractual arrangements. Hopes were that Public-Private Part- nerships in the water sector would provide an efficient management of resources, more and better allocated investments, a reduction of the fiscal burden and thereby would contribute to increase both the coverage of the network and the quality of service delivery. Private participation in the water sector is a very controvertial issue. Due to ideological considera- tions but also to real economics, social and environmental questions, there is for the moment no real consensus on the impact of water partial privatisation on the access of the poor, and the quality of water. Indeed, private water companies may provide sub-optimal service quality levels, as they do not take into account the extensive health externalities, such as pollution (Shirley, 2000). The privatization of the water services could also hurt the poor, due to price increases, investment only in lucrative areas, and service payment enforcement (Estache, Gomez-Lobo and Leipziger, 2001; Birdsall and Nellis, 2002). On the other hand,
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Morphological road segmentation in urban areas from high resolution satellite images

Morphological road segmentation in urban areas from high resolution satellite images

This problem is not of recent interest in literature, since we can find works on the subject that date back to the 1970s [3], and passed through several generations of acquisition sys- tems with radical methodological and application changes [4, 5]. In former works based on mid-resolution sources, the so- lution has been often limited to the detection of non-urban or main urban roads, like in [5], while in more recent times the attention moved on high resolution imagery, with the devel- opment of several automatic and semiautomatic techniques for urban roads detection [6, 7, 8, 9]. Different methodolo- gies and approaches have been proposed, from tracking based methods [10], where the detection process relies on the gener- ation of seeds that help following the road structures along the images, techniques based on shape analysis [11], to the meth- ods based on higher order active contours, like in [12, 13], that typically need a higher computational effort. To not forget are also general segmentation techniques that whether properly defined can provide road extraction as a by-product, as is the case of recent texture-based segmentation techniques [14, 15] Since many of these methods, but the works of Peng’s et al. [12, 13], above all those aiming at the automatic extraction of road information, has proved their potentials only in simple scenarios, and are likely to fail in complex environments like dense urban areas, in this paper we decided to take back into consideration the use of morphological analysis to cope with this problem, and present here a technique of road segmenta- tion that completely relies on such image processing domain. This choice is justified by the fact that the current resolutions provide data with a considerable richness in fine details, that implicitly enhances the geometric properties of the detected scenes.
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Adapting to urban displacement : the use of cash transfers in uraban areas

Adapting to urban displacement : the use of cash transfers in uraban areas

Finally, regarding beneficiaries’ living conditions in general, cash can also replace many other forms of assistance, including shelter, livelihoods and the provision of basic items. An impact evaluation was conducted on the UNHCR operation in Amman in 2009 104 and revealed that 94% of respondents use cash grants to pay rent and 90% to purchase food. Moreover, 93% of respondents emphasized the positive impact of cash on the situation of their family including better housing, greater quantity/quality food, diminished debt, better medicine, children started attending school and better living conditions. This is a good example of how cash grants are used for more than one need and an illustration of the reason why the objectives of unconditional cash transfers are usually framed broadly. In Jordan, cash grants are provided to Iraqi refugees to replace the provision of food and non-food items, support refugees to pay for the fees to access some public services, pay for their rent and utilities and enjoy minimum acceptable standard of living. This wide range of objectives permits to take into account the flexible use of cash grants due to the differences of priorities set by households. Furthermore, cash can specifically target other needs than food. For instance, UNHCR in South-Africa provides emergency shelter assistance since refugees and asylum-seekers are usually excluded from government-funded housing programs and xenophobic attacks force refugees to move away from the townships where accommodation is cheaper to inner cities where rent is more expensive. UNHCR steps in to pay rent directly to private accommodation owners or to emergency shelter providers on behalf of vulnerable refugees and asylum-seekers.
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Innovations in Barge Transport for Supplying French Urban Dense Areas: A Transaction Costs Approach

Innovations in Barge Transport for Supplying French Urban Dense Areas: A Transaction Costs Approach

2. Second, the barge-truck system implemented by Norbert Dentressangle for Franprixreveals the sitespecificity of river ports in major cities. Indeed, the scarcity of available space on the docks, combined with increasing traffic jams (and thus the prospect of the inexorable rise of environmental taxation), justifyFranprix’s strategic choice to take in advance a strategic position in the heart of Paris through long-term contracts with Port de Paris and Paris Terminal. The increase of river logistics can’t but raise urban docks' degree of sitespecificity. Several ways are possible to reduce this specificity. One of them comes from the fact that, in urban areas, the relevant unit of loading is often the pallet or the mini-container rather than the container. At that level,one must look for economies of scale necessary for urban river logistics. This observation has led the Dutch to innovate – unsuccessfully – with Distrivaart, a barge that carries palletized goods between distribution centers and supermarkets (Wiegmans, 2005). In terms oftransactional analysis, Distrivaart internalized theservices usually providedin the warehouse, namely,managementof pallets andloading and unloadingof vehicles. Italso had theadvantage of eliminatingstevedoring usually made by a terminal operator and thento reduce thedegree of site specificityof riverdocks.Developingurbanriverlogisticsinvolves rethinkingthe scopeand attributes ofSTs included in thistransaction.
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Comparing Urban Agriculture in Four Areas of Portland: Mapping and Survey Results

Comparing Urban Agriculture in Four Areas of Portland: Mapping and Survey Results

Support for the City of Portland’s role in encouraging and supporting urban agriculture appears to be strong. Moving forward, we suggest that policymakers consider the motivations we have listed here when considering how best to foster community participation or frame discussion about urban food production. Despite Portland’s global renown for sustainability planning, framing issues in terms of environmental concerns or sustainability may not resonate with everyone, whereas framing issues in terms of motivations that appear to be more universal – fun, freshness, and healthy eating – may prove more fruitful for policymakers and planners, and may lead to more active community engagement in public policymaking and planning efforts. More specifically, we offer the following suggestions for ways to support home gardeners:
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Urban gravity in the global container shipping network

Urban gravity in the global container shipping network

4.2 Gravitational properties of the networks The results obtained from the application of the gravity model, which has eight continental dummies on origin and destination, and are standardizes on “Europe”, are summarized in Table 2 (see details for the functions estimated in Appendix 2b). They confirm that the maritime distance of intercity links has a negative influence on shipping flows among cities, and this effect negatively increases with node aggregation and network density, namely from gateway to city-region, and from space-L to space-P as in the results in section 4.1. The year dummy (linear variable) is positive meaning that constant term’s effect also increased over time between 1977 and 2016 for the expansion of containerization and the improvement of maritime transport technology. As in section 4.1, while the continental dummies while the continental dummies for North and Latin America are positive for DWTs, the one of Africa is negative due to fewer liner services and insufficient container terminal development. Population has the expected positive sign, with an increase from gateway/space-L to city-region/space-P, thus confirming as in Figure 5 that larger cities connect more with each other. Last but not least, we observe that city-region/space-P has a higher Adj. R-square than gateway/space-P so that central places take the lead in explaining maritime flows compared with gateways because they are a more suitable definition reflecting extended hinterlands and complex shipping structures. Those results mean that the global container shipping network is highly gravitational and thus can be considered as a coherent system where flows, nodes, and geography are mutually interdependent.
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Regression Analysis of Travel Indicators and Public Transport Usage in Urban Areas

Regression Analysis of Travel Indicators and Public Transport Usage in Urban Areas

Nelson and his colleagues [7] found that rail transit system in Washington DC has congestion reduction benefits to motorists. Preferring public transport to private car to develop sustainability and reducing the frequency of car usage is contemplated in ample studies [2], [5], [8] and [9]. However, in order to gain accurate and reliable results designers need to consider urban travel behavior, urban transport costs and public transport infrastructure in different contexts. Therefore, this research intends to assess the impacts of some important travel modes indicators on public transport trips in various cities around the world using one relationship model that was rarely addressed in previous literature. Although there are considerable studies on the different types of urban mobility indicators and public transport, there are only a few researches that examined the relationships between urban mobility indicators in different cities around the world [10]-[20]. Therefore, this research tries to find the relationship between urban mobility indicators and public transport usage by evaluating walking, cycling, private motorized trips, and public transport indicators in different cities. The results can be used to propose sustainable strategies during urban planning process.
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A Global Navigation Management Architecture Applied to Autonomous Robots in Urban Environments

A Global Navigation Management Architecture Applied to Autonomous Robots in Urban Environments

Fig. 6. Some screenshots of the environment perception system illustrate the management during the road following and intersection maneuvers tasks. was set to 10 m, regarding the GPS and OSM errors. Figure 5 shows the global navigation movement performed by the APPACHE for each CP in the Global Routing Table II. In this figure, we could predict the state transitions diagram through which our navigation task have been during each step of the process (states given by the management system). This state transition have been validated by the results obtained in Figure 6. So, not only did our system achieve the goal, but at each level of the task, it could perfectly identify intersections and provide a reference trajectory to be followed (yellow line on the screenshorts of Figure 6). In this Figure, the vehicle always follows the yellow line. The Red line means wrong way road and the green line means right way (or feasible way, but not the one to be followed). Each time a road intersection is approached, the Global Management component outputs an image with two lines (in our scenario) representing the way to take and all other ways with different color than yellow according to the feasibility of the direction. Approaching the GOAL POINT, we can see that the line feature outputed delimit the location of the goal by painting in dark all the point of the line situated after this GOAL POINT.
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Agricultural management in peri-urban areas. The experience of an international workshop

Agricultural management in peri-urban areas. The experience of an international workshop

Sustainability of peri-urban agriculture [Eq. 1] where GPP [gC day-1] is the gross primary productivity, εmax [gC MJ-1] is the maximum radiation use efficiency coefficient, f (Tmin) and f (VPD) are scalar functions [0,1] of the minimum daily temperature (Tmin, °C) and vapour pressure deficit (VPD, Pa), introduced to keep account of the reduction in εmax due to non-optimal growth conditions. From daily GPP values, net photosynthesis (PSNnet, gC day-1) is obtained by subtracting the maintenance respiration. NPP is estimated annually as the cumulative sum of PSNnet less the cost of annual maintenance and growth respirations. The model requires several eco-physiological parameters specific for grasslands. The detailed list of parameter values used in this study can be found in Colombo et al. (2009). According to Eq. 1, the model input variables are the fraction of photosynthetically active radiation absorbed by plants (fAPAR), the incident PAR [MJ m-2 day-1], and the minimum, maximum and mean temperature values, used to derive the scalar functions f (Tmin) and f (VPD). Daily PAR values were obtained from incident global radiation (GRAD) measurements at the Sondrio meteorological station, applying an empirical relation (PAR=GRAD*0.48, Tsubo and Walker, 2005). Temperature values were obtained from the same station. Lastly, fAPAR values were obtained from the Normalized Difference Vegetation Index (NDVI), derived from MODIS satellite data, using the empirical relationship proposed by Sellers et al. (1994). NDVI time series were generated from the standard 16-day 250m spatial resolution MODIS vegetation indices product (MOD13Q1), downloaded for the period 2001-2007 from the NASA Warehouse Inventory Search Tool (WIST https://wist.echo.nasa.gov). To exclude low quality data and reduce noise in the NDVI time series, the filtering algorithm proposed by Chen et al. (2004) was used. Lastly, a linear relationship between consecu- tive observations was assumed in order to obtain daily NDVI data for the whole study period. The output of this procedure is the hay meadows daily GPP and PSNnet, and annual NPP maps, over the whole study area.
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iGPS: Global Positioning in Urban Canyons with Road Surface Maps

iGPS: Global Positioning in Urban Canyons with Road Surface Maps

iGPS: Global Positioning in Urban Canyons with Road Surface Maps Vincent Drevelle and Philippe Bonnifait Abstract—Interval Global Positioning with road Surface (iGPS) is a new method to obtain a robust and continuous po- sitioning in urban areas by tightly-coupling precise 3-D drivable area maps with GPS pseudorange measurements. Map and GPS measurements are represented by geometric constraints, thus turning the localization problem into a constraint satisfaction problem whose solution is the confidence domain of position. Interval analysis is employed to solve the problem by using contractions and bisections of a prior position box. If more than 3 satellites are visible, the method is robust to erroneous pseudorange measurements. The system is also able to compute multiple position hypotheses where there are ambiguities. An ex- perimental validation using real GPS pseudorange measurements and a precise 3-D map is reported to illustrate the performance of the method with real data in an urban area, and with reduced satellite visibility. Confidence domains are consistent with the ground truth throughout the 1 km trial, and a 6.5 m 95% accuracy is achieved with at least two satellites in view.
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Prioritizing the provision of urban ecosystem services in deprived areas, a question of environmental justice

Prioritizing the provision of urban ecosystem services in deprived areas, a question of environmental justice

2 1. Introduction Numerous studies have stressed the importance of quantifying urban ecosystem services (UES) at different scales and integrating them into decision-making processes (Ernstson et al. 2010; Kremer et al. 2016; Yang et al. 2018). However, while the concept of UES represents a bridge between social and ecological systems within a city, little is known about the relationship between social systems and ecosystem services delivery at the local level (Amini Parsa et al. 2019). This issue is increasingly addressed within the environmental justice (EJ) framework, given the recognition of urban green spaces (UGS) and their UES as local solutions to both local (e.g. air pollution, intense precipitation events) and global environmental burdens (e.g. climate change) (Zhao and Sander. 2015; Amini Parsa et al. 2019; Escobedo et al. 2019) and the growing conviction that uneven exposure to environmental burdens and benefits among social groups affects city sustainability (Baró et al. 2019). The concept of EJ was mainly developed in the USA in the 1970s, with a focus on the relationship between socioeconomic groups and the distribution of environmental burdens and benefits, assuming that disadvantaged communities are most exposed to environmental risks (Greenberg and Cidon. 1997; Agyeman et al. 2002; Kruize et al. 2007; Brown et al. 2012; Raddatz and Mennis. 2013; Boyce et al. 2016). The application of EJ framework to UES focuses on their immediate distribution at the local scale (e.g. city-scale, block group, neighborhood) where ecosystem services delivery and benefits are realized (Baró et al. 2019) and hence can support policies of sustainability to maintain their long-term production in a fair and just manner (de Groot et al. 2010; Boone and Fragkias. 2013).
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A comparative performance analysis of position estimation algorithms for gnss localization in urban areas

A comparative performance analysis of position estimation algorithms for gnss localization in urban areas

task of the receiver. It consists to compute the user position, velocity and time. C. GNSS Measurement Model The GNSS positioning is based on trilateration method (cf.figure 2) [2]: the distance between user and satellites is measured by multiplying the travel time by the speed of light and its expressed as functions of the satellites and user coordinates. Travel time is measured by comparing the time of emission (provided by the satellite) with the time of reception (measured by the receiver). The Satellite clocks can be synchronized with a global GNSS time using information contained in the navigation message broadcasted by satellites. However, the offset between user clock and GNSS time cannot be predicted and needs to be estimated at the same time as the position. Thus, the GNSS measurement models that
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Pregnancy vulnerability in urban areas: a pragmatic approach combining behavioral, medico-obstetrical, socio-economic and environmental factors

Pregnancy vulnerability in urban areas: a pragmatic approach combining behavioral, medico-obstetrical, socio-economic and environmental factors

on PTB appears to be more discussed 18 – 20 , 22 . According to a recent review of the literature, there is some sugges- tive evidence of adverse associations with environmental noise, especially for LBW 23 , 24 . Otherwise, few studies demonstrate a benefic effect of maternal proximity to green spaces on BW 25 , 26 . However, most studies focus on only one determinant or one class of determinant and/or their influence on pregnancy outcome (when considered, the other determinants are treated as potential confounding variables). So, the distribution of all these determinants and how they potentially accumulate in the population of pregnant women is still largely unknown. Considering simultaneously all of these determinants could help define a concept of global vulnerability. This concept of vulnerability is very broad here: it is not only a socio-economic vulnera- bility but an interaction between various causes: genetic, socio-economic, psychological and environmental… To our knowledge, such a descriptive approach was never conducted in a large pregnant women population-based study.
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Introduction. Global City, Take 2: A View from Urban History

Introduction. Global City, Take 2: A View from Urban History

essential feature of the world, which affects national policies and international relations ‘to a hitherto unprecedented degree’. 13 th century Venice, 16 th century Mexico or Goa, early modern Constantinople, late 19 th century New York City, and you see municipal authorities and urban societies, aside with monarchies or national governments when available, coming to grasps with the question of transcultural urban landscapes and polyglot societies and facing major disjunctures in the history of the community. One of the answers that was provided was urban segregation, and scholars are beginning to explore painstakingly the actual implementation of globally diffused segregationist ideas, linking it to transnational capital flows and flows of political support. 45 Cities have also been sites for temporary migrations, such as those generated by pilgrimages or tourism. There again, urban historians can suggest some dots on the ‘i’ and crosses on the ‘t’ of globalization, by showing how much the impact and responses to these momentaneous irruptions have changed Mecca, Roma, Benares or the cities from the European Rivieras and the South East Asia seashore over centuries. Similar suggestions could be made for each of Appadurai’s scapes. Just consider briefly that values such as freedom and identity and other major values and ideals have been assembled and maintained in urban settings, that newspapers, news agencies or radios and televisions are living from an about city news, that a host of technologies have emerged, spread or
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How Principals Exercise Transformative Leadership in Urban Schools in Disadvantaged Areas in Montréal, Canada

How Principals Exercise Transformative Leadership in Urban Schools in Disadvantaged Areas in Montréal, Canada

All three principals had something to say about social justice and were therefore cognisant of this concept. However, each has a different perspective about the issue, which can be seen in Table 3. For Charlene, social justice is evident in results (‘Social justice is present when everyone can be who he/she wants to be’) and for these results to be achieved, she sees equity as a major goal within the context of diversity. Equity means educational and instructional services that are not offered on an equal basis but rather tailored to every student’s needs. She also promotes equity in learning by offering diverse and differentiated services to students who themselves are diverse. Empowerment is another goal for teaching with equity: teachers will teach content in a way that empowers students and opens them to the world. This is where a school can make a difference for children living in poverty. She values justice, respect and the belief in every student’s capacity to learn, and she warns that both she and the school team have to guard against any injustice that they themselves could create in the school. At the same time, she would like her school team to be more critical and open to, and interested in, the social movements happening outside the school, such as the Occupy Montréal movement or the six months of student demonstrations in Québec to protest against tuition fee increases.
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Synthetic Aperture Radar : Algorithms and Applications in Forests and Urban Areas

Synthetic Aperture Radar : Algorithms and Applications in Forests and Urban Areas

The AfriSAR campaign aims to provide support to forthcoming NISAR, GEDI and BIOMASS missions. Using UAVSAR and the LVIS waveform Lidar instruments, NASA ac- quired 39.6 and 32.4 of flight hours of data, respectively over various sites in Gabon for the sake of calibration, verification, and new algorithm exposition of several ecosystem science products. The operating band of the UAVSAR radar instrument is 1217.5-1297.5 MHz (L- band), (data can be downloaded from https://uavsar.jpl.nasa.gov/cgi-bin/data.pl), which exploits an electronically scanned array antenna to allow a robust repeat-pass interfero- metric measurements [ Hensley et al. , 2008 ]. The Gulfstream III jet, with an acceptable flight altitude of 12.5 km, allows the scanning of about a 22 km wide area, with incidence angles extending from 25 degree to 60 degree. A typical UAVSAR polarimetric single-look- complex (SLC) product has ground range and azimuth resolution of 2.5 m and 1.0 m, re- spectively [ Fore et al. , 2015 ]. In the following, we show the tomographic imaging over the northern part of the Lopé National Park in Central Gabon using 7 PolInSAR single-look- complex images collected by UAVSAR. The total area covered by the image is 22 km x 50 km, but a part of approximately 1 km x 5 km is considered for our study. UAVSAR dataset acquired over Lopé is fully polarimetric and has been gathered by increasing the aircraft al- titude by 20 m each flight track, leading to significantly low variation of vertical resolution from near range to far range. (we present the acquisition parameters of UAVSAR configu- ration in Table 4.2 , also baseline configuration of the acquisitions is shown in Table 3.3 ).
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A global multinational survey of cefotaxime-resistant coliforms in urban wastewater treatment plants

A global multinational survey of cefotaxime-resistant coliforms in urban wastewater treatment plants

426 427 Sample size coliforms : <5 °C n=77, >15 °C n=72; sample size CTX-R coliforms <5 °C n=76, >15 °C n=72. Box plots show percentiles together with medians; whiskers show the minimum and maximum values. A version of these data

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A survey of wheat take-all in Belgium

A survey of wheat take-all in Belgium

The FI levels observed were always high and did not allow to safely identify the growing conditions where take-all risks are very important. Previous crop effect In the figure 5, it appears clearly that as previous crop wheat and pasture are favorable to a higher level of infection by take-all. With other crops, TAI is lower and any difference can be made between them. Often presented as a previous crop increasing the infection risk (Becker and al, 1998), winter barley give in this survey a moderate level of TAI, but with only two plots.
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