1,720,961 research outputs found
e-Quantum leap on a data highway: Planning for electric minibus taxis in sub-Saharan Africa’s paratransit system
Full text linkThis is a book chapter on the Minibus taxis are ubiquitous in the developing cities of the Global South.Minibus taxis are ubiquitous in the developing cities of the Global South. This versatile, if somewhat chaotic, public transport system is now faced with the need to move to renewable energy. But the looming roll-out of electric vehicles poses a threat to the already fragile electrical grids of African cities. This chapter evaluates the energy requirements of decarbonisation and evaluates two types of data, passenger-based and vehicle-based, from research in South Africa that has modelled these taxis. Using these two data capture methods, we assess the energy requirements and charging opportunities for electric minibus paratransit in three African cities and compare the results of the two methods to assess their suitability for planning minibus taxi electrification
Agent-based modelling of paratransit as an intelligent complex adaptive system to improve efficiency
Full text linkThesis (PhD)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Urban residents in Sub-Saharan Africa (SSA) face mobility challenges that limit theiraccess to jobs, services, markets, and socioeconomic opportunities. In most SSA cities,public transport is predominantly provided by the inefficient paratransit system – a flex-ible mode of passenger transport consisting of privately-owned, low-capacity unscheduledminibuses and motorcycle taxis. There is growing interest among city authorities andurban transport researchers in addressing the inefficiency problem associated with para-transit. Several approaches, such as complete overhaul to bus rapid transit (BRT), andphased banning of paratransit from the cities have previously been proposed and con-comitant implementation projects started. However, most of such projects have eitherfailed to take off, or they have stalled. This is likely because of the huge capital invest-ment required, the unique social and cultural dynamics associated with “third world”countries, and urban sprawl due to poor city planning. This study departs from the com-mon perspective held by several researchers and city authorities who view paratransit as“chaotic”, thus, the justification for its total overhaul and banning. Instead, this studyaims to leverage the beneficial aspects of existing paratransit – such as flexibility, demand-responsiveness and near-ubiquitous coverage – with the elusive objective of achieving amore efficient paratransit state as a result.Through theoretical modelling, field study and experimental approaches, this studyaimed to improve the efficiency of minibus taxis paratransit systems. The theoretical mod-elling work involved modelling paratransit systems as complex adaptive systems (CAS)and developing an agent-based model (ABM) for minibus taxi operations in an organically-evolved paratransit setting. The field study involved an in-depth investigation of minibustaxi operations in Kampala’s paratransit system, and collection and analysis of minibustaxi movement data that was used to validate the agent-based model. The experimen-tal approaches involved three separate simulation experiments, simulating the minibustaxi transportation dynamics with varying levels of agents’ intelligence and situational awareness. Machine learning methods, such as random forests and convolutional neuralnetworks were used to train agents in the subsequent simulation experiment to improvetheir intelligence during decision making. At each stage, several efficiency metrics’ valuessuch as passenger waiting time and minibus taxi occupancy were collected. The resultsfrom the experiments showed that there was an improvement in the overall efficiency ofthe minibus taxi paratransit system. For instance, the average passenger waiting time re-duced from 1.2 hours to 30 minutes, indicating a 55% improvement. Whereas the averageminibus taxi occupancy increased from 42% to 51%, indicating a 21% improvement. Ac-cordingly, we concluded that improving the micro-level agents’ intelligence and situationalawareness, results in an overall increase in the efficiency of the paratransit system.To the transportation researchers, we recommend further work on using ABM toinclude other modes of paratransit transport such as the three-wheeled rickshaws andmotorcycle taxis (boda bodas). To the city authorities, we recommend the integration ofsmart mobility and ICT applications into the paratransit ecosystem to support journeyplanning, booking, scheduling, and fare collection.AFRIKAANSE OPSOMMING: Stedelike inwoners in Afrika Suid van die Sahara (SSA) word gekonfronteer met mo-biliteitsuitdagings wat hul toegang tot werk, dienste, markte en sosio-ekonomiese geleen-thede beperk. In die meeste SSA-stede word openbare vervoer oorheersend aangebieddeur die ondoeltreffende paratransit-stelsel -’n buigsame manier van passasiersvervoerwat bestaan uit private lae-volume busse en huur-motorfietse. Daar is toenemende be-langstelling onder stadsowerhede en navorsers van stedelike vervoer om die ondoeltref-fendheidsprobleem so eie aan paratransit. Verskeie benaderings, soos byvoorbeeld dievolledige opknapping van busvervoer (BRT) en ’n gefaseerde verbod op paratransit instede, is voorheen voorgestel en verwante implementeringsprojekte is van stapel gestuur.Die meeste van hierdie projekte het egter nie daarin geslaag om te begin nie, of hulleis gestaak. Dit is waarskynlik as gevolg van die groot kapitaalinvestering wat benodigword, die unieke sosiale en kulturele dinamika wat verband hou met lande van die ”derdewˆereld” en stedelike uitbreiding as gevolg van swak stadsbeplanning.Hierdie studie wyk af van die algemene perspektief wat deur verskeie navorsers en stad-sowerhede gehou word, wat paratransit as “chaoties” beskou, en dus van die regverdigingvir die totale opknapping en verbod daarvan. In plaas daarvan beoog hierdie studie omdie voordelige aspekte van paratransit te versterk - soos buigsaamheid, aanvraagresponsi-witeit en byna alomteenwoordige dekking - met die hoop om ’n doeltreffender paratransit-staat as gevolg daarvan te bewerkstellig.Deur middel van teoretiese modellering, veldstudies? en eksperimentele benaderings,het hierdie studie ten doel gehad om die doeltreffendheid van minibustaxi-paratransitstelselste verbeter. Die teoretiese modelleringswerk behels die modellering van paratransitstelselsas komplekse aanpasbare stelsels (CAS) en die ontwikkeling van ’n agent-gebaseerde model(ABM) vir minibustaxibedrywighede in ’n organies-ontwikkelde paratransit-omgewing.Die veldstudie behels ’n diepgaande ondersoek na minibustaxibedrywighede in Kampala se paratransit-stelsel, en versameling en ontleding van minibustaxibewegingsdata wat ge-bruik is om die agent-gebaseerde model te bekragtig. Die eksperimentele benaderings hetdrie afsonderlike simulasie-eksperimente behels, wat die minibustaxi-vervoerdinamika metverskillende vlakke van agente se intelligensie en situasiebewustheid simuleer. Masjienleer-metodes soos ewekansige woude en evolusionˆere neurale netwerke is gebruik om agente indie daaropvolgende simulasie-eksperiment op te lei om hul intelligensie tydens besluitnem-ing te verbeter. In elke stadium is verskeie waardes vir doeltreffendheid soos die passasier-swagtyd en die besetting van minibustaxi’s versamel. Die resultate van die eksperimentehet getoon dat die algehele doeltreffendheid van die minibus-paratransitstelsel verbeterhet. Byvoorbeeld, die gemiddelde passasierwagtyd verminder van 1,2 uur tot 30 minute,wat dui op ’n 55% verbetering. Terwyl die gemiddelde besetting van minibustaxi van 42%tot 51% gestyg het, wat dui op ’n verbetering van 21%.Gevolglik het ons tot die gevolgtrekking gekom dat die verbetering van die intelligensieen situasiebewustheid van die mikrovlakagente tot ’n algehele toename in die doeltreffend-heid van die paratransitstelsel lei.Vir die vervoernavorser beveel ons verdere ABM-werk aan om ander maniere vanparatransit-vervoer soos die driewiel-riksja’s en motorfiets-taxi’s (boda bodas) in te sluit.Aan die stadsowerhede beveel ons die integrasie van slim mobiliteit- en IKT-toepassingsaan in die paratransit-ekosisteem om reisbeplanning, bespreking, skedulering en tariefin-vordering te ondersteun.Doctora
Transforming Paratransit in Africa's congested Cities: An ICT- enabled Integrated Demand Responsive Transport (iDRT) approach
Full text linkThis is a conference paper on developing cities in Africa and the Global South are grappling with the problem of inadequate public transport provision.Developing cities in Africa and the Global South are grappling with the problem of inadequate public transport provision. The informal privately-run paratransit system consisting of mini- and micro-buses, shared taxis (jitneys), motorcycle and bicycle taxis has seen substantial growth since the early nineties.
This loosely-regulated transport system is associated with many challenges that include congestion, high crash rates, high levels of noise and air pollution. In this paper we describe the origin and current status of this structurally unique paratransit system. We then reviewed the transport master plans of four East African cities (Dar es Salaam, Kampala, Kigali, and Nairobi) and identify remaining planning gaps. We found that all the four cities reviewed lacked satisfactory plans for multi-modal public transport integration, demand responsiveness, and ICT integration which are essential to every modern and efficient public transport system. We then proposed a conceptual organised public transport system (ICT-enabled iDRT). We described how it could be adapted for a highly congested city like Kampala in order transform its existing chaotic paratransit system into an efficient public transport system that could make commuters happier and safer, reduce costs and considerably reduce pollutio
Characterizing the movement patterns of minibus taxis in Kampala’s paratransit system
Full text linkThis is a research article about urban travelers in Africa depend on minibus taxis for their daily social and business commutingUrban travelers in Africa depend on minibus taxis for their daily social and business commuting. This paratransit system is loosely regulated, self-organizing, and evolves organically in response to demand. Our study used floating car data to analyze and describe the movement characteristics of nine minibus taxis in Kampala, Uganda. We made three intriguing findings. Firstly, in searching for, picking up and transporting passengers, minibus taxi trajectories followed a heavy-tailed power-law distribution similar to a “L´evy walk”. Secondly, their routes’ topology and shape gradually changed. Thirdly, the extraordinary winding (expressed in terms of tortuosity) of the paths suggested the extreme determination of the drivers’ search for passengers. Our findings could help city planners to build on the self-organizing characteristics of the minibus taxi system, and improve the mobility of travelers, by optimizing routes and the distribution of public amenities
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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