• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 28
  • 18
  • 3
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 64
  • 64
  • 21
  • 21
  • 16
  • 12
  • 10
  • 10
  • 9
  • 9
  • 9
  • 8
  • 8
  • 8
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Melhoria do desempenho do tráfego em rotatórias com o emprego de semáfaros próximos na via principal / Traffic performance improvement at roundabouts with traffic lights near the main street

Neris, Diego Fernandes 24 February 2014 (has links)
Neste trabalho é avaliado o desempenho operacional de uma nova configuração idealizada para a operação de rotatórias de três pernas (prioridade para os veículos da via principal com semáforos próximos). Nesta avaliação é comparado o novo sistema de operação com outros dois usualmente empregados: (1) prioridade para os veículos que estão circulando na ilha central (rotatória convencional) e (2) prioridade para os veículos da via principal sem o emprego de semáforo, bem como, com base nos resultados das comparações realizadas, são estabelecidas as condições dos fluxos de tráfego em que é indicada uma ou outra configuração. Os valores obtidos nas simulações mostram, de forma inequívoca, o desempenho operacional superior da rotatória com prioridade para a via principal com semáforos próximos, adequadamente programados, no caso de fluxos altos. O emprego de semáforos próximos reduz significativamente o atraso na aproximação crítica e, em consequência, o tamanho da fila, como consequência do aumento expressivo da capacidade de tráfego da rotatória. Os resultados da simulação corroboram o que se pode observar nos sistemas implantados na cidade de Araraquara, onde a colocação de semáforos próximos de rotatórias de três pernas melhorou de forma significativa o desempenho operacional dos dispositivos, reduzindo o atraso crítico e o tamanho da fila crítica e aumentando a capacidade. O acompanhamento da acidentalidade nas rotatórias onde foram colocados semáforos próximos na cidade de Araraquara mostra uma redução dos acidentes graves de aproximadamente 90%. Uma explicação para essa redução pode ser devido ao aumento da paciência dos motoristas em esperar uma brecha maior para entrar na rotatória, pois sabem que, esporadicamente, há uma interrupção do fluxo na via principal. / In this study the operational performance is measured of a new idealized configuration for the operation in three-legged traffic circles (priority way for the vehicles from the main street with traffic lights nearby). This measured is compared the new operational system with two others usually systems: (1) priority for the circulating traffic (conventional roundabout) and (2) priority for vehicles from the main street without traffic lights. Also, based on the results from the comparisons, seek to establish what traffic flow conditions are better for a given configuration. The values obtained from the simulations demonstrate, clearly, the superior operational performance of the traffic circle with main road priority combined with properly programmed traffic lights nearby, in the case of high flows. The use of traffic lights reduces significantly the delay from the critical approach, and consequently, the queue length, as a consequence resulting on significant traffic capacity increase at the intersection. Simulation results validate what can be seen in Araraquara, where the installation of traffic lights near from the three-legged traffic circle improved significantly the operating performance of the devices, reducing the critical delay and critical queue size and increasing the effective capacity. Monitoring the accident rate in traffic circles where traffic lights nearby were placed in Araraquara shows a reduction of approximately 90% in serious accidents. An explanation of this reduction may be due to the increased of patience of drivers in wait for a larger gap to enter on the roundabout, because they know there will be an interruption on the main street, sporadically.
42

Service quality improvement through lean management at King Khalid International Airport in Saudi Arabia

Almuharib, Tariq Mohammed January 2014 (has links)
This thesis aims at investigating the level of service at departure area of KKIA. The study further measures the perceived quality of service and passenger satisfaction in term of tangibles, reliability, responsiveness, assurance and empathy by using five steps of lean six sigma (Define, Measure, Analyse, Improve and Control). The study aims to implement and evaluate the effectiveness of using a lean six-sigma managerial approach to the departure area of KKIA to enhance the level of service (LOS) and customer satisfaction. The passenger flow through the airport is used to measure the quality of services. Existing studies that discuss lean six-sigma implementation in airports were evaluated. Data was collected about KKIA departure area and its LOS both before and after the lean six-sigma implementation. Additionally, a SERVQUAL questionnaire was used to evaluate pre- and post-implementation review. The questionnaire features easy-to-collect data to measuring the perceived quality of service and evaluate passenger satisfaction with the LOS in KKIA. Before the study concepts of LOS and Lean was unheard within the airport community. Initial evaluation show poor customer service and many delays (waste) within the departure are at KKIA. During the study a growing awareness of Lean and LOS showed improvements in the customers’ experience, e.g, removing the shop at the entrance, improving flow thought the airport. Concluding the study, there was a total reduction in waiting from 54.74 minutes to 34.87 minutes (35.7% reduction). Also the LOS on the IATA Performance Standard went from E (Inadequate) to C (Good). This is improvement, excellent but without continuous improvements the Airport’s LOS will reduce back as passenger numbers grow from 16 million passengers per year (up from 9.8 million in 2004), to an expected 25 million by 2025. Interesting different cultural approaches to lean management became evident during the study when compared to other implementations in Europe to the Middle East. Cultural difference will always affected the reliability of the results. However, by considering these cultural effects in answering questions and interviews, the lean implementation was still successful. As culture changes are ongoing, evaluation of the situation at KKIA is required for ongoing improvements. Best-practice for the continued improvement of ongoing lean management is suggested for the departure area at KKIA. These key strategies and best-practice approaches are useful to future implementations at other airports.
43

Model za utvrđivanje uticaja izdvojenih nesignalisanih pešačkih prelaza na nivo usluge gradskih saobraćajnica / The influence of an unsignalized midblock crosswalk on the level of service of urban street segments estimating model

Garunović Nemanja 09 October 2020 (has links)
<p>Predmet ove doktorske disertacije su izdvojeni pešački prelazi odnosno njihov uticaj na uslove odvijanja motornog saobraćaja na gradskim saobraćajnicama. Ocenu uslova odvijanja motornog saobraćaja na gradskim saobraćajnicama između ostalog vrši se na osnovu brzine putovanja vozila prolaznog toka na odseku koja je u obrnuto proporcionalna sa vremenom putovanja vozila na odseku gradske saobraćajnice. Povećanje vremena putovanja zavisi od veličine ostvarenih vremenskih gubitaka koji nastaju na izdvojenom pešačkom prelazu. Ključna pretpostavka na kojoj je zasnovana ova doktorska disertacija je da vremenski gubici vozačkih tokova na izdvojenom pešačkom prelazu nastaju usled pojave pešaka (ili grupa pešaka) i kao takvi utiču na smanjenje prosečne brzine putovanja tj. povećanje vremena putovanja vozila na odseku. U skladu sa tim cilj rada je definisanje modela za utvrđivanje vremenskih gubitaka vozila na izdvojenim pešačkim prelazima uz mogućnost implementacije u postojećoj metodologiji za definisanje uslova odvijanja saobraćaja na odsecima gradskih saobraćajnica. U skladu sa definisanim ciljem izvršena je analiza prethodnih relevantnih istraživanja, a zatim i prikupljane podatka o uslovima odvijanja saobraćaja u realnom saobraćajnom toku. Sistematizacijom prikupljenih podataka i primenom odgovarajućih matematičkih i statističkih alata utvrđene su zakonitosti nastanaka vremenskih gubitaka vozačkih tokova koji nastaju na izdvojenom pešačkom prelazu i formiran model za njihov proračun.</p> / <p>The theme of this doctoral thesis is the analysis of the midblock pedestrian crossings influence on traffic conditions on urban street segments. The assessment of motor traffic conditions on urban street segments was carried out on the basis of travel speed of through vehicles. Travel speed of through vehicles for the segment represents the relation between the segment length and segment running time, which implies that running time increase directly affects travel speed decrease. Segment running time greatly depends on the value of the achieved delays which occur on a midblock pedestrian crossing. The key assumption, which this doctoral thesis is based on, is that delays of vehicular flows on midblock pedestrian crossings occur as a consequence of pedestrian (or a group of pedestrians) appearance and that they affect the travel speed of through vehicles decrease, that is, the increase of segment running time. Accordingly, the purpose of this paper is defining the model for determination of vehicular delays on midblock pedestrian crossings, with the possibility of its implementation into the existing methodology for defining traffic conditions on the urban street segments. In accordance with the defined aim within the doctoral thesis, the analysis of previous relevant research studies was carried out, and then the research in a real traffic flow. The systematization of the collected data and the application of the appropriate mathematical and statistical tools enabled how to establish the rules of vehicular flows delays occurrence on midblock pedestrian crossing. On the basis of the established rules and correlation of traffic and geometric characteristics of midblock pedestrian crossings, a model for calculating the value of delays occurring in traffic flows was defined.</p>
44

Fotgängares gånghastigheter i bytespunkter för kollektivtrafik

Jegenberg, Minna, Lundström, Kristina January 2017 (has links)
Walking speeds are an important parameter in the process of designing for example arenas, malls and station environments, to be able to make them safe and comfortable for the users. Previous studies have mainly focused on pedestrian walking speeds at zebra crossings and the results of these are the basis for traffic signal timing. The studies have also investigated the relationship between walking speed and gender, age and density of pedestrians. From the results of these studies, conclusions have been drawn that these three factors have an impact on pedestrian walking speeds. To make microsimulations of pedestrians reflect reality as well as possible, pedestrian walking speeds should be investigated at regular intervals, as walking speeds change with the ongoing change of the composition of the population. In the simulation of station environments, pedestrian speeds should also be used that have been measured in these types of environments. Alternatively, the speeds should be measured at locations near stations, rather than using speeds from zebra crossings. As a step in improving the above-mentioned microsimulations, the aim of this work is to study walking speeds at a public transport hub during rush hour. The work also focuses on connecting walking speeds to each sex and level of crowding. To achieve this goal, video recordings were performed at the exchange point between Stockholms östra and Tekniska högskolan in Stockholm, Sweden, where public transport passengers change between light rail and subway. Analysis of the video films resulted in walking speeds which were higher than those previously measured at zebra crossings. The most obvious factors explaining this are the differences in the environment where the studies were conducted and that the walking speeds in this thesis were measured during rush hour. The results show that simulations of stations and locations nearby should not be based on walking speeds measured at zebra crossings. Analysis of the video films also resulted in the calculated mean walking speed of women being marginally lower than for men. Regarding the link between density of pedestrians and their walking speeds a conclusion can be drawn that at low densities pedestrians have good opportunities to freely select their own walking speed. The freely chosen walking speed which can thus be maintained at low densities can vary widely between different individuals. At higher, unlike at lower densities, it is difficult for pedestrians to maintain a freely chosen speed due to interactions with other pedestrians. The calculated average walking speed at higher densities therefor decreases as the density increases. Interactions with other pedestrians can either mean that a pedestrian is forced to lower the speed or that he or she must walk faster to keep up with the current pace. When analyzing the video films, several other factors effecting the walking speed could be noted. Of these factors, grouping of pedestrians and if the pedestrian is using a phone or carrying luggage could be seen to decrease the pedestrian speed. These factors’ impact on walking speeds was only superficially studied in this thesis, and no reliable conclusions can therefore be drawn. Keywords: Pedestrian walking speed, public transport traffic hub, density of pedestrians, Level of
45

Level-of-service And Traffic Safety Relationship: An Exploratory Analysis Of Signalized Intersections And Multiland High-speed Arterial Corridors

Almonte-Valdivia, Ana 01 January 2009 (has links)
Since its inception in 1965, the Level-of-Service (LOS) has proved to be an important and practical "quality of service" indicator for transportation facilities around the world, widely used in the transportation and planning fields. The LOS rates these facilities' traffic operating conditions through the following delay-based indicators (ordered from best to worst conditions): A, B, C, D, E and F. This LOS rating has its foundation on quantifiable measures of effectiveness (MOEs) and on road users' perceptions; altogether, these measures define a LOS based on acceptable traffic operating conditions for the road user, implying that traffic safety is inherent to this definition. However, since 1994 safety has been excluded from the LOS definition since it cannot be quantified nor explicitly defined. The latter has been the motivation for research based on the LOS-Safety relationship, conducted at the University of Central Florida (UCF). Using data from two of the most studied transportation facility types within the field of traffic safety, signalized intersections and multilane high-speed arterial corridors, the research conducted has the following main objectives: to incorporate the LOS as a parameter in several traffic safety models, to extend the methodology adopted in previous studies to the subject matter, and to provide a platform for future transportation-related research on the LOS-Safety relationship. A meticulous data collection and preparation process was performed for the two LOS-Safety studies comprising this research. Apart from signalized intersections' and multilane-high speed arterial corridors' data, the other required types of information corresponded to crashes and road features, both obtained from FDOT's respective databases. In addition, the Highway Capacity Software (HCS) and the ArcGIS software package were extensively used for the data preparation. The result was a representative and robust dataset for each LOS-Safety study, to be later tested and analyzed with appropriate statistical methods. Regarding the LOS-Safety study for signalized intersections, two statistical techniques were used. The Generalized Estimating Equations (GEEs), the first technique, was used for the analyses considering all periods of a regular weekday (i.e. Monday through Friday): Early Morning, A.M. Peak, Midday, P.M. Peak and Late Evening; the second technique considered was the Negative Binomial, which was used for performing an individual analysis per period of the day. On the other hand, the LOS-Safety study for multilane high-speed arterial corridors made exclusive use of the Negative Binomial technique. An appropriate variable selection process was required for the respective model building and calibration procedures; the resulting models were built upon the six following response variables: total crashes, severe crashes, as well as rear-end, sideswipe, head-on and angle plus left-turn crashes. The final results proved to be meaningful for the understanding of traffic congestion effects on road safety, and on how they could be useful within the transportation planning scope. Overall, it was found that the risk for crash occurrence at signalized intersections and multilane high-speed arterial corridors is quite high between stable and unacceptable operating conditions; it was also found that this risk increases as it becomes later in the day. Among the significant factors within the signalized intersection-related models were LOS for the intersection as a whole, cycle length, lighting conditions, land use, traffic volume (major and minor roads), left-turn traffic volume (major road only), posted speed limit (major and minor roads), total number of through lanes (major and minor roads), overall total and total number of left-turn lanes (major road only), as well as county and period of the day (dummy variables). For multilane-high speed arterial corridors, the final models included LOS for the road section, average daily traffic (ADT), total number of through lanes in a single direction, total length of the road section, pavement surface type, as well as median and inside shoulder widths. A summary of the overall results per study, model implications and each LOS indicator is presented. Some of the final recommendations are to develop models for other crash types, to perform a LOS-Safety analysis at the approach-level for signalized intersections, as well as one that incorporates intersections within the arterial corridors' framework.
46

Examining the Youth Level of Service/Case Management Inventory in the Context of Reliability, Validity, Equity, and Utility: A Six-Year Evaluation

Flores, Anthony W. January 2013 (has links)
No description available.
47

Nivo usluge na nesignalisanim pešačkim prelazima / Level of service at unsignalized pedestrian crossings

Mitrović Simić Jelena 14 March 2016 (has links)
<p>Istraživanje koje je sprovedeno u okviru disertacije poslužilo je za definisanje matematičkog modela koji se može primeniti u postupku određivanja nivoa usluge za nesignalisane pešačke prelaze. Formirani model za proračun stepena propuštanja pešaka u uslovima lokalnog odvijanja saobraćaja zavisi od protoka pešaka i vozila, strukture saobraćajnog toka (učešće autobusa i teretnih vozila) i smera kretanja vozila na lokaciji pešačkog prelaza. U okviru disertacije izvršena je analiza pešačkih intervala prilikom prelaska kolovoza. Uporednom analizom prihvatljivih i kritičnih intervala dobijen je model ponašanja pešaka u zavisnosti od karakteristika lokacije nesignalisanog pešačkog prelaza. Utvrđena je zavisnost između dužine prihvaćenih intervala pešaka prilikom prelaska kolovoza i uslova odvijanja saobraćaja, polnih karakteristika pešaka i broja pešaka koji prelaze kolovoz na nesignalisanom pešačkom prelazu.</p> / <p>The study, which was conducted within the thesis, has served to define a mathematical model that can be applied in the process of determining the level of service at unsignalized pedestrian crossings. The formed model for motorist yield rate, in terms of the local pedestrian traffic flow, depends on pedestrian and vehicular flow rate, traffic flow structure (the share of buses and freight vehicles), and vehicle moving at the location of a pedestrian crossing. The pedestrian gap acceptance behaviour has also been analysed. Comparative analysis of acceptable and critical pedestrian gap was conducted. Model of pedestrian behaviour, which depending on the site characteristics, was formed and it has been proven a correlation between the length of the accepted pedestrian gaps and the roadway and traffic conditions, gender characteristics and the number of pedestrians at unsignalized crossings.</p>
48

Analysis of Automated Vehicle Location Data from Public Transport Systems to Determine Level of Service

Eriksson, Charlotte, Jansson, Olivia January 2019 (has links)
Many cities suffer from problems with high traffic flows in the city centers which leads to a desire to get more people to choose public transport over cars. For many car drivers, the main reason to take the car is the convenience and time efficiency; the price is often of less importance. The public transport providers should, therefore, strive to improve their Level of Service (LOS). A general process that can be used by public transport providers or other stakeholders to evaluate the LOS in a public transport system based on Automated Vehicle Location (AVL) data is developed and presented in this thesis.The process values the quality and suitability of the AVL data, propose which KPIs to use and how to use the results to find possible improvements. Four different types of erroneous data were discovered: outliers in position, outliers in speed, outliers in travel time and general errors. KPIs are developed in three main areas: on-time performance, travel time distribution and speed, where each KPI is divided into several sub-areas.
49

Adaptação do HCM-2000 para determinação do nível de serviço em rodovias de pista simples sem faixas adicionais no Brasil / Adaptation of the HCM-2000 to estimate the level of service for two-lane highways without auxiliary lanes Brazil

Egami, Cintia Yumiko 04 May 2006 (has links)
O objetivo desta tese é adaptar os procedimentos do Highway Capacity Manual 2000, para que possam melhor estimar a qualidade de serviço nas condições de tráfego encontradas em rodovias de pista simples estudadas. Para isto, foi desenvolvido um programa para calibração automática do simulador TRARR, baseado em um algoritmo genético e implementado em Perl. A calibração, que usa dados de velocidade e porcentagem de veículos em pelotões, coletado por meio de filmagens nos locais estudados, foi feita simultaneamente para cinco trechos diferentes, para que o simulador fosse capaz de reproduzir as características de um trecho típico de rodovia de pista simples do estado de São Paulo. Para garantir a qualidade dos resultados das simulações realizadas com o modelo recalibrado, procedeu-se à sua validação, usando-se um conjunto independente da dados. Partindo-se do pressuposto que a estrutura geral do método deveria ser mantida, a adaptação do HCM-2000 consistiu em obter novos valores para os diversos fatores de ajuste usados no processo de estimativa do nível de serviço. Para tanto, foram reproduzidos os experimentos de simulação realizados no desenvolvimento do procedimento para análise de rodovias de pista simples, à exceção do uso da versão recalibrada TRARR no lugar do simulador TWOPAS. Os fatores de ajuste adaptados foram: fator de pico horário (PHF), fator de ajuste de rampas (fG), fator de equivalência veicular (ET), fator para o efeito de zonas de ultrapassagem proibida (fnp) e fator de ajuste para o efeito combinado da divisão direcional do tráfego e de zonas de ultrapassagem proibida (fd/np). Com exceção do PHF, todos os demais fatores foram obtidos a partir de resultados de simulação. Os níveis de serviço observados nos cinco trechos estudados foram comparados com estimativas obtidas com a versão original do HCM-2000 e com a adaptação proposta. Os resultados desta comparação mostram que as estimativas obtidas com a adaptação proposta são mais precisas que as obtidas usando-se os valores originais do HCM-2000. / This thesis objective is to adapt the Highway Manual Capacity 2000, procedures to produce better estimates of service level and capacity for two-lane highways studied, In order to do this, an automatic calibration system, implementing a genetic algorithm and coded in Perl, was used to obtain a recalibrated version of TRARR, a two-lane highway simulation model. The calibration, that which uses speed and percent vehicles traveling in platoons data collected by videotaping, was carried out simultaneously for five different road segments, so that the recalibrated model would be able to reproduce traffic behavior on a typical two-lane road in the state of São Paulo, Brazil. The recalibrated model was validated using a second, independent, set of data. Based on the assumption that the general framework of the methodology should be kept, the adaptation was achieved by obtaining new values for the adjustment factors used in the procedure. Thus, the simulation experiments used in the development of HCM-2000 methodology were reproduced using the recalibrated TRARR model. The following adjustment factors were adapted: peak hour factor (PHF), grade adjustment factor (fG), heavy vehicle equivalence factor (ET), adjustment factor for the effect of non-passing zones (fnp) and adjustment factor for combined effect of directional distribution of traffic and percentage of no-passing zones (fd/np). With the exception of the PHF, all factors were obtained from simulation results. In order to assess the accuracy of the proposed adaptation observed levels of service were compared to the estimates obtained through the original HCM-2000 procedure and the modified procedure. The results of these comparisons clearly show that the estimates obtained using the proposed values for the adjustment factors are closer to the observed levels of service than the estimates obtained using the original values for the adjustment factors.
50

Evaluation of drivers\' behavior performing a curve under mental workload / Avaliação do comportamento dos condutores para realizar uma curva sob distração mental

Vieira, Fábio Sartori 20 April 2016 (has links)
Driving under distraction may lead drivers to wrong actions that can result in serious accidents. The objective of this thesis was to apply a driving simulator to verify variations in drivers\' behavior while driving. Behavior to drive on a curve was measured by variation in drivers\' speed profile in a virtualized highway. The comparison was performed between two identical simulations, one involving drivers distracted with a mental workload, and other in which they were full aware of driving task. 54 volunteer drivers took part in this study, which was divided into 4 stages. 17 drivers performed the distraction test known as PASAT, and results showed that distracted drivers did not recognize the beginning of the curve and drove through it at speeds higher than those when they were fully aware. Moreover, driving performance was increased when drivers were aware of driving, thereby hitting high speeds in tangents, but perceiving curves in advance to reduce acceleration. This study confirms that driving simulators are beneficial in discovering drivers\' behavior exposed to activities that could be highly risky if driving in real situations. / A distração durante a atividade de direção pode levar o condutor de veículos automotores a cometer falhas, que podem ocasionar até mesmo acidentes graves. Este estudo aborda a utilização de simuladores de direção para verificar variações no comportamento de motoristas ao realizar a atividade de direção, distraídos ou com plena atenção na condução do veículo. O comportamento é medido pela variação no perfil de velocidade dos condutores para desenvolver uma curva considerada perigosa em uma rodovia simulada em ambiente virtual. A variação de velocidade deste perfil é comparada entre duas simulações idênticas, onde em uma delas os condutores estão distraídos com um teste que proporciona estresse mental e, na outra, estão com plena atenção à direção. 54 condutores fizeram parte deste estudo dividido em 3 etapas. 17 participantes realizaram o teste de distração conhecido como PASAT, e a análise dos resultados mostram que, distraídos, os condutores não perceberam o início da curva e desenvolveram velocidades maiores durante seu trajeto. Além disso, quando estavam com plena atenção à atividade de direção, o desempenho dos condutores foi melhor, atingindo velocidades maiores nas tangentes, mas percebendo as curvas antecipadamente e reduzindo suas velocidades antes de iniciar esses trechos.

Page generated in 0.0457 seconds