Dissertations / Theses: 'Roundabouts'

1

He, Yi. "Safety Effectiveness Analysis of Roundabouts in Louisiana." Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10683149.

Full text

Abstract:

Louisiana currently has 30 roundabouts in operation and hundreds of roundabouts in the planning and design stage. The Louisiana Department of Transportation and Development (DOTD) is very interested in knowing the safety performance of existing roundabouts in the state.

As revealed in this paper, the safety effectiveness of a roundabout depends on its prior traffic control type, conformity to the geometric design guidelines, changes in layout of intersection, and nighttime lighting conditions. All 19 roundabouts investigated by this study demonstrated significant reduction in injury crashes because of lower operating speed, reduced right-angle collisions, and elimination of head-on and left turn crashes. Based on changes in the number of conflicting points and traffic control method, it is understandable why the most significant and consistent safety improvement was associated with the roundabouts previously controlled by stop signs on minor streets. The Crash Modification Factor (CMF), as estimated by the Empirical Bayes (EB) method, for this group of roundabouts is 0.28 with a standard deviation of 0.054. The roundabout is economically justified for its safety benefit alone based on the benefit-cost ratio analysis for this group of roundabouts.

The study did identify a few compounding factors at the individual intersections, such as questionable geometric design elements, increased number of conflicting points, unpredictable human behavior, and lack of lighting at night.

APA, Harvard, Vancouver, ISO, and other styles

2

Linse, Leif. "Capcal for small roundabouts : Current status and improvements." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-63822.

Full text

Abstract:

Questions have been raised regarding how good Capcal works for roundabouts with a weaving length smaller than 25 meters and if Capcal would work for weaving lengths lower than the 16 meters that is the lower limit in the current model. In this thesis, two possible improvements has been developed and tested on five roundabouts with a weaving length less than 25 meters. Work has been done to build alternative gap acceptance models ranging from removal of the 16-meter limit through re-estimation of the current model to a completely new model. In this thesis a new sub model has been introduced that take into account the uncertainty of if circulating vehicles will exit or continue to circulate. These sub models have been combined in 29 different ways including the current Capcal model configuration and have been tested with five different roundabouts. The conflict delay, which is caused by interaction with other vehicles, has been used to compare the model results with delay observations from video captures of the roundabouts. Out of all model configurations, the original Capcal 3.3 model had the lowest difference in average between the model result and the observations. If the 16-meter weaving length restriction in the original model is removed, almost the same results are obtained as with the restriction. While none of the model configurations improved the model fit, no configuration could be statistically be rejected. In the results of individual roundabouts, there were differences between the model and observations of up to 50%. This shows that while this thesis could not find any improvements of Capcal, there is a potential for future work to develop improvements of the roundabout model.
I nuläget tillåter Capcal att växlingssträckor ner till 16 meter modelleras, men i dataunderlaget som användes vid skapandet av nuvarande modell finns endast med en cirkulationsplats under 25 meter. Det har lyfts frågetecken kring huruvida Capcal ger bra resultat för cirkulationsplatser med en växlingssträcka på mindre än 25 meter samt huruvida modellens nedre gräns på 16 meter skulle kunna tas bort. I detta examensarbete har två olika möjligheter att förbättra modellen testats på fem olika cirkulationsplatser med växlingssträcka kortare än 25 meter. I arbetet har det ingått att ta fram alternativa gap-acceptance-modeller vilka sträcker sig från att enbart ta bort 16-metersgränsen via en nyestimering av Capcals modell till en helt ny modell. Därtill har en ny submodell skapats som tar hänsyn till den osäkerhet som uppstår kring huruvida cirkulerande fordon kommer att köra ur cirkulationen vid en utfart eller fortsätta cirkulera. De utvecklade submodellerna samt nuvarande Capcal modell har kombinerats i 29 olika kombinationer. Dessa 29 kombinationer har för varje av de fem studerade cirkulationsplatserna testats mot observationer från respektive cirkulationsplats. Konfliktfördröjningen, vilket är fördröjning på grund av interaktion med andra fordon, har använts för att jämföra Capcal-resultaten och observationerna. Av alla modellkonfigurationer så gav nuvarande Capcal 3.3-modell lägst medelskillnad mellan modellresultat och observationer. Om 16-meter-restriktionen i nuvarande Capcal-modell tas bort, så fås i stort sett samma resultat. Ingen av de studerade modell-förändringarna gav en bättre passning mellan modell och verklighet i medel, men ingen förändring kunde förkastas ur statistisk synvinkel. Det var dock stora variationer i resultaten för enskilda cirkulationsplatser med upp till 50% skillnad mellan modellens resultat och observerade värden. Detta visar på att även om detta examensarbete inte lyckades hitta några förbättringar av Capcal, så finns det potential för framtida arbete att ta fram förbättringar av cirkulationsplatsmodellen i Capcal.

APA, Harvard, Vancouver, ISO, and other styles

3

Xu, Feng. "Driver behavior and gap acceptance studies at roundabouts." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442865.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Okezue, O. G. "Design and evaluation of signal controlled highway roundabouts." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376698.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Elbadrawi, Hesham Roshdy. "A computer simulation model for single-lane roundabouts." FIU Digital Commons, 2000. http://digitalcommons.fiu.edu/etd/3131.

Full text

Abstract:

During the past three decades, the use of roundabouts has increased throughout the world due to their greater benefits in comparison with intersections controlled by traditional means. Roundabouts are often chosen because they are widely associated with low accident rates, lower construction and operating costs, and reasonable capacities and delay. In the planning and design of roundabouts, special attention should be given to the movement of pedestrians and bicycles. As a result, there are several guidelines for the design of pedestrian and bicycle treatments at roundabouts that increase the safety of both pedestrians and bicyclists at existing and proposed roundabout locations. Different design guidelines have differing criteria for handling pedestrians and bicyclists at roundabout locations. Although all of the investigated guidelines provide better safety (depending on the traffic conditions at a specific location), their effects on the performance of the roundabout have not been examined yet. Existing roundabout analysis software packages provide estimates of capacity and performance characteristics. This includes characteristics such as delay, queue lengths, stop rates, effects of heavy vehicles, crash frequencies, and geometric delays, as well as fuel consumption, pollutant emissions and operating costs for roundabouts. None of these software packages, however, are capable of determining the effects of various pedestrian crossing locations, nor the effect of different bicycle treatments on the performance of roundabouts. The objective of this research is to develop simulation models capable of determining the effect of various pedestrian and bicycle treatments at single-lane roundabouts. To achieve this, four models were developed. The first model simulates a single-lane roundabout without bicycle and pedestrian traffic. The second model simulates a single-lane roundabout with a pedestrian crossing and mixed flow bicyclists. The third model simulates a singlelane roundabout with a combined pedestrian and bicycle crossing, while the fourth model simulates a single-lane roundabout with a pedestrian crossing and a bicycle lane at the outer perimeter of the roundabout for the bicycles. Traffic data was collected at a modern roundabout in Boca Raton, Florida. The results of this effort show that installing a pedestrian crossing on the roundabout approach will have a negative impact on the entry flow, while the downstream approach will benefit from the newly created gaps by pedestrians. Also, it was concluded that a bicycle lane configuration is more beneficial for all users of the roundabout instead of the mixed flow or combined crossing. Installing the pedestrian crossing at one-car length is more beneficial for pedestrians than two- and three-car lengths. Finally, it was concluded that the effect of the pedestrian crossing on the vehicle queues diminishes as the distance between the crossing and the roundabout increases.

APA, Harvard, Vancouver, ISO, and other styles

6

Gbologah, Franklin E. "The impacts of illumination on nighttime safety at roundabouts." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54453.

Full text

Abstract:

Roundabout installations are becoming common practice among DOTs and other local governments due to their superior safety attributes compared to other conventional at-grade intersections, especially stop-control and uncontrolled intersections. Current U.S. national guidelines for roundabout illumination recommend systematic illumination for all roundabouts. This recommendation might become a potential hindrance to desired widespread installations due to implied financial costs, especially in rural areas because the competing stop-control and uncontrolled intersections can be kept unlit. Interestingly rural roundabouts in most countries around the world are not illuminated as indicated by a recent survey of international roundabout illumination policies and standards from 45 countries. Also, review of intersection safety literature does not identify any publication that supports a systematic illumination policy of U.S. roundabouts. In fact, despite this recommendation there is no quantitative research on influence of illumination levels on nighttime safety at roundabouts and little on conventional intersections. Conversely, the literature shows a significant number of published studies which have indicated that currently recommended illumination levels on roadways can be reduced without compromising nighttime safety. This dissertation evaluates the link between roundabout crashes and different illumination levels. At the beginning of this dissertation research, there was no available repository of quantitative intersection illumination levels which could be used in highway safety research. Also, existing protocols for measurement require expensive light meters and are extremely time consuming to follow, making them impractical to use to study a large number of intersections. Consequently, this dissertation first evaluates the relationship with the best available data. The best available intersection illumination data was obtained from the Minnesota data contained in the Highway Safety Information System (HSIS). Minnesota crash and illumination data from 2003 to 2010 were analyzed. This illumination data was a qualitative description of intersection illuminating schemes and/or luminaire arrangement. Therefore, this dissertation also developed a cost-effective, accurate, and rapid method for measurement of quantitative intersection illumination data, and applied the developed protocol to a case study in Georgia. The measured intersection illumination was analyzed together with crash data obtained from GDOT for 2009 to 2014. The results of a naive analysis on the best available data indicated among other findings that the presence of lighting can provide approximately 61 percent lower total nighttime crash rate compared to the unlit condition. Also, providing illumination to the roundabout circle alone can yield about 80 percent of the benefits (55 percent reduction from unlit condition) of illuminating both the roundabout circle and approaches (66 percent reduction from unlit condition). Field test results for the camera calibration indicate that the average intersection illuminance derived from the protocol is within 4 percent difference of the actual average intersection illumination estimated from following the existing protocols. Next, despite limited roundabout data and potential issues of selection bias which could not be addressed in this dissertation, a cautious roundabout illumination specific crash modification factor was estimated with a negative binomial regression model. The model results showed that an increase of 1 lux in average roundabout illuminance will result in a 4.72 percent reduction in expected number nighttime crashes. The results of this work are useful in creating a sound framework for DOTs and other transportation agencies to determine the most appropriate level of illumination for roundabouts. This study also makes a number of significant contributions to highway safety research. First, this work is the first quantitative study on the impact of illumination on safety at roundabouts. The status-quo for highway safety research regarding the impacts of illumination had been to treat road lighting as a binary (Lit/Unlit) variable. However, even in most places without purposely-built road lighting there is usually ambient lighting from abutting facilities such as a gas stations or a store. Second, this dissertation is the first documented application of the photographic method to roundabouts. It is also the first documented application of the photographic method’s camera specific constant calibration approach to transportation field measurements. Previous documented application of the photographic method to transportation field measurements used an exposure specific calibration approach. Unlike the camera specific constant calibration approach, the exposure specific approach is rigid and field measurements must always be done at the exposure settings used in calibrating the camera. Thirdly, this work demonstrates the first developed procedure to developing uniformity (contour) plots from the photographic method. Next, this work can serve as the basis for initial efforts to create an illumination specific quantitative crash modification factor. Currently, the Highway Safety Manual is lacking in this important safety parameter. Last, but not the least this work offers procedures for collecting luminance data from the field and also documents a database of intersection illumination levels and intersection characteristics which can be used by future research.

APA, Harvard, Vancouver, ISO, and other styles

7

Toussant, Erica A. "Analyzing the Impacts of Driver Familiarity/Unfamiliarity at Roundabouts." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1451907184.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Jackson, Meredith A. "Do Roundabouts Work? An Evaluation for Uniform Approach Demands." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76831.

Full text

Abstract:

With the increased prevalence of roundabouts in the United States, there is a need to evaluate the performance of roundabouts relative to other intersection control strategies. Few studies have compared roundabouts with other intersection control strategies in a systematic fashion. Consequently, this Thesis compares four types of intersection control strategies considering a single lane approach with a 58 km/hr speed limit and equal demand on all approaches. The study demonstrates that vehicle delay is minimized with the use of a roundabout intersection control for all demand levels below 500 veh/hr/approach. Above this point if the left turn percentage exceeds 70% traffic signal control is more efficient. The roundabout alternative also produces the fewest vehicle stops for low demand levels, low left turn demand and high right turn demand, however a TWSC alternative produces the least number of vehicle stops when the through and total demand is high. This study illustrates that fuel consumption and carbon dioxide, carbon monoxide, hydrocarbon and nitrogen oxide emissions can be improved with roundabout control over other intersection control strategies. The research presented here demonstrates that for low traffic demand levels roundabouts should be part of design alternatives considered for isolated intersection control.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

9

Rescot, Robert Andrew. "Automating traffic studies at modern roundabouts a feasibility study /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5025.

Full text

Abstract:

Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 12, 2009) Includes bibliographical references.

APA, Harvard, Vancouver, ISO, and other styles

10

Ren, Liang. "Development and Validation of New Capacity Models for Roundabouts." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/367372.

Full text

Abstract:

There is increased interest in building modern roundabouts in Europe, Australia and North America because of the safety and operational benefits that can be realized from this type of intersection. With this interest comes the increasing need to be able to estimate the capacity, evaluate the performance and analyze the emission levels that a roundabout will be likely to provide once it is built. In the early 2000s, a National Cooperative Highway Research Program (NCHRP) study was conducted that, among other tasks, developed single-lane roundabout capacity estimation equations. These equations, presented in the Highway Capacity Manual 2000 and 2010 (referred to as HCM 2000 and 2010 hereafter), can be calibrated using locally determined values for the critical gap and follow-up time. Other models, such as the German Highway Capacity Manual (referred to as GHCM) and SR45 models are also widely used in estimating capacity around the world. However, some studies have indicated that the existing models could under or overestimate roundabout capacity because some important factors, such as headway distribution type, proportion of exiting vehicles and heavy goods vehicles, are not taken into account.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

APA, Harvard, Vancouver, ISO, and other styles

11

Flanagan, T. B. "Signal controlled roundabouts : An investigation into the efficiency of signal controlled roundabouts utilizing simulation techniques with particular reference to junctions with three approaches." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376678.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Godavarthy, Ranjit Prasad. "Network and design concepts for accommodating large trucks at roundabouts." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/15061.

Full text

Abstract:

Doctor of Philosophy
Department of Civil Engineering
Eugene Russell
It has been well documented that roundabouts can offer several safety and operational benefits over signalized and stop controlled intersection alternatives. However the growing use of roundabouts and their benefits could be greatly diminished because they may not be well designed for large trucks, or to accommodate oversize/overweight (OSOW) vehicles which may be essential to a state’s industry and economy. This dissertation addresses concepts to better design roundabouts for use by owners/operators of typical large trucks, and that will also accommodate OSOW vehicles where appropriate. Roundabout safety generally decreases with increased roundabout size, wider lanes and larger radii, the geometric parameters that benefit large trucks and OSOW, thus a better balance is needed. This study accomplishes this balance by initially reviewing and incorporating those portions of the study “Accommodating Oversize Overweight Vehicles at Roundabouts” that were researched, completed and written by the author of this dissertation, and which compiled current practice, research and concerns by various U.S. states and concerns of the trucking industry, by conducting four different surveys. Then to meet these concerns expressed by survey respondents, a great number of possible accommodation, strategies and design templates were developed by using existing design software. An evaluation method was also developed. Two additional, needed studies, not previously reported in any published literature, addressed : 1. a vertical, ground clearance analysis, and 2. a study of the use of roundabouts in urban freight networks to incorporate their inherent benefits ,such as, reducing congestion, delay and pollution. The first analysis described above was conducted by using software with 3D analysis capabilities to check and recommend critical vertical grades and maximum dimensions for a range of large truck types and OSOW vehicle configurations. Guidelines were developed to avoid problems of low, ground clearance vehicles scraping roundabout surfaces (“hanging up”). The second study used existing software that relates intersection types to intersection traffic flow efficiency and related pollution, on a number of routing scenarios to test the hypothesis that integration of roundabouts in these freight networks improves traffic flow, and decreases delay, congestion and pollution. The results were mixed but the procedure is sound and should be beneficial for future use by researchers and decision makers.

APA, Harvard, Vancouver, ISO, and other styles

13

Lepitre, Mark. "Inter-textual Indirection in Heartbreak House : disregarded roundabouts and failed provocations." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28410/28410.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Tang, Shengjie. "Traffic safety analysis for cyclists at roundabouts, a case study in Norrköping." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149424.

Full text

Abstract:

Cyclists as vulnerable road users are oftentimes unprotected with exposed human body, can fall easily and sustain serious injuries when encountered collisions, especially with motorists. At roundabouts, accident reduction rate for cyclists is rather uncertain or sometimes less favorable compared to other road users (e.g. motorists, pedestrians). This thesis focuses on advancing the understanding of traffic safety issues for cyclists at roundabouts by identifying concerns faced by cyclists and evaluating their designs to find out which configuration has high or higher safety level towards cyclists. The research approach adopted in this work includes a wide review of relevant literature on cyclist safety and roundabouts and the implementation of empirical research, the latter was carried out through a Case Study in Norrköping city by obtaining cyclist related accident data from Swedish Traffic Accident Data Acquisition database to identify roundabouts with high cyclist-related accidents in the city assisted with PTV Visum Safety tool and fetching traffic volume from city network model operated by Norrköping Municipality for each identified roundabout. The main findings from this research conclude that single-lane roundabouts with separated cycle paths in high traffic volume setting provide better or higher safety performance for cyclists compared to other roundabout configurations.

APA, Harvard, Vancouver, ISO, and other styles

15

Diamond, Alexandra Jane. "An investigation into the roles of slits and roundabouts during vertebrate limb development." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231142.

Full text

Abstract:

Slits and their Roundabout (Robo) receptors were identified based on their role in regulating axon guidance, but are known to play multiple roles in development, including regulating heart development and myoblast migration. There are 3 vertebrate Slits (Slit1 – 3) and 4 Robos (Robo1 – 4), and previous work has demonstrated expression of Slit and Robo family members in and around developing joints where their function is unclear. Mutations in human Robo3 have been linked to degenerative joint disorders, such as scoliosis and rheumatoid arthritis. Misregulation of other members of the Slit/Robo signalling pathway is also reported in cells from arthritic joints. This suggests that Slit/Robo signalling is required for normal joint development and/or maintenance, though our understanding of their roles in these processes is rudimentary. The central question of my thesis is to determine the role/s of Slit/Robo signalling in limb and joint development. In situ hybridisation confirmed strong expression of Slits and Robos throughout mouse limb and joint development, though no expression of Slit1 or Robo3 was detected. Analysis of Slit1/2, Slit3 and Robo1 mutant (loss-of-function) mice revealed normal limb development, however misexpression of dominant-negative Robo2 during chicken limb development caused shortening of cartilage elements. To begin to identify molecular changes that may compensate for the loss of Slit/Robo signalling I demonstrated members of the Sema3/PlexinA/Nrp axon guidance family are expressed in patterns comparable to those of Robo1, Robo2 and Slit3. I discovered that PlexinA1 is downregulated in Slit3 mutant mouse limbs. My results suggest the role for Silt/Robo signalling may be more complex than previously thought and do not define a clear role for signalling during limb development. My results suggest the role for Silt/Robo signalling may be more complex than previously thought and do not define a clear role for signalling during limb development. Previous work has linked Slit/Robo signalling to development of degenerative joint disorders, and I propose some hypotheses as to how Slit/Robo signalling could cause bone and joint defects.

APA, Harvard, Vancouver, ISO, and other styles

16

Khliefat, Ibrahim Hashim. "Analysis and Modeling of Drivers Perception of Quality of Service on Urban Roundabouts." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1421254328.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Ibrahim, Kamarulzaman Bin. "Bayesian techniques for the evaluation of road traffic safety measures : an application to small roundabouts." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480602.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Zhao, Min [Verfasser], Karsten [Akademischer Betreuer] Lemmer, Dirk [Akademischer Betreuer] Söffker, and Meike [Akademischer Betreuer] Jipp. "Modeling Driving Behavior at Single-Lane Roundabouts / Min Zhao ; Karsten Lemmer, Dirk Söffker, Meike Jipp." Braunschweig : Technische Universität Braunschweig, 2019. http://d-nb.info/1180601513/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Zhao, Min Verfasser], Karsten [Akademischer Betreuer] [Lemmer, Dirk [Akademischer Betreuer] Söffker, and Meike [Akademischer Betreuer] Jipp. "Modeling Driving Behavior at Single-Lane Roundabouts / Min Zhao ; Karsten Lemmer, Dirk Söffker, Meike Jipp." Braunschweig : Technische Universität Braunschweig, 2019. http://d-nb.info/1180601513/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Alqahtani, Abdullah Ayed F. "Comparative Analysis of Roundabout Capacity Analysis Methods." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1557252181941848.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Whalen, James. "An investigation into the structure of operational control of driving during the negotiation of urban roundabouts." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/792158/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Mosslemi, Marjan. "Using Metering Signals at Roundabouts with Unbalanced Flows to Improve the Traffic Condition : The Case Study of Kannik Area in Stavanger." Thesis, Linköping University, Department of Science and Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16429.

Full text

Abstract:

In some roundabouts, just relying on the "right of way" regulations results in long queues forming along the approaches. This usually happens when a roundabout suffers from unbalanced flow patterns (one or two of the approaches convey much heavier traffic compared to the others). There is an idea that signalization of roundabouts can be useful as a countermeasure for such a problem, especially during peak hours. In that case, signal operation can come in many forms, including full-time control, part-time control, or metering. One problem that seems to be facing engineers when signalizing roundabouts is lacking a general set of patterns or guidelines to choose an appropriate form of signalization and apply it efficiently in different situations. There is also a need for a comprehensive review over the available literature concerning signalization of roundabouts. In this thesis, a review of literature regarding signalization of roundabouts is carried out. Moreover, a roundabout in Stavanger with unbalanced traffic flows is studied in order to find an appropriate signalization scenario which can improve the traffic situation. The network is modeled and simulated in AIMSUN.

APA, Harvard, Vancouver, ISO, and other styles

23

Mahmood, Kashif. "Improving Roundabout Performance Using Roundabout Metering Technique." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1463499775.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Åkerström, Erika. "Korsningen Industrigatan-Östgötagatan i Linköping : analys och åtgärder." Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2480.

Full text

Abstract:

Trafiksystemet i Linköpings tätort bygger på två ringar, Y-ringen (yttre) och C- ringen (centrum), vilkas syfte är att avlasta stadens olika centrala delar. Den signalreglerade korsningen Industrigatan-Östgötagatan är en del av den så kallade Y-ringen och under vissa tider på dygnet finns det risk för köbildning. Antalet inkommande fordon i korsningen uppgick år 1999 till ca 28 000 per dygn och idag uppgår antalet till någonstansmellan 30 400-32 400 fordon/dygn.

Kommunen har planer på att på att etablera ett bostadsområde i Övre Vasastaden, vilket kan komma att påverka trafikmängderna i den studerade korsningen. En garanterad orsak till ökade trafikmängder är det faktum att Linköping ständigt ökar i invånarantal, med ökad folkmängd ökar även trafiken. Storleken på trafikökningen finns prognostiserad i olika trafikprognoser och dessa visar att när staden har 150 000 respektive 180 000 invånare kommer det inkommande flödet i aktuell korsning uppgå till ca 35 000 respektive ca 40 000 fordon/dygn. Framtida kö- och framkomlighetsproblem är därmed en realitet.

Med stöd av effektberäkningsprogrammet Capcal presenteras tre olika förslag på åtgärder där framkomlighetsproblemen undviks. Alternativ 1 innebär modifiering av trafiksignalerna och en förbjuden vänstersväng, alternativ 2 är en rund cirkulationsplats och alternativ 3 motsvaras av en oval cirkulationsplats. I de två sistnämnda alternativen föreslås även fyra alternativa lösningar för gång- och cykeltrafik.

En jämförelse mellan de olika alternativen visar att de ”bästa” effektmåtten erhålls vid alternativ 3 även om resultaten i alternativ 2 nästan är lika ”bra”. Däremot om kommunens prognoser skulle slå fel med 10 %, dvs om trafiken skulle öka med 10 % mer än beräknat, skulle endast alternativ 1 visa på godkända värden. Resonemanget kring rekommendationer av alternativ har delvis gjorts utifrån de framräknade effektmåtten men även med tanke på trafiksäkerheten för både de oskyddade trafikanterna och fordonstrafikanterna.

APA, Harvard, Vancouver, ISO, and other styles

25

Yap, Yok Hoe. "Modelling roundabout capacities." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/380010/.

Full text

Abstract:

There has been extensive research and development into the capacity of modern offside priority roundabouts since the 1970’s. Despite this, there remains a major gap in existing knowledge with regards to the factors and variables which affect roundabout entry capacity. This is reflected in the differences and inconsistencies in inputs and methodologies between existing state-of-the-art models. Evaluations with recent data collected from 35 roundabout entry lanes in the field have shown that this limits the accuracy of state-of-the-art models, particularly in their ability to explain site-to-site variation in entry capacities. New empirical models have thus been developed for lane capacity using regression, and benchmarking against neural networks showed that they performed well with the shortlisted explanatory variables. These regression models were based on exponential-in-Qc and linear-in-Qc forms, and outperformed existing state-of-theart models. In the new models, entry-exit separation distance and exiting flows on the same arm were found to be more useful predictor variables (when used in conjunction with other variables) compared to others used in more-established models (e.g. entry radius and entry angle). To investigate the effects of separation distance and exiting flows through microscopic simulation, stochasticity in separation distances was modelled through a novel approach in Vissim involving multiple exit connectors. This was significant as the variability of separation distances had not been explored before, whether through analytical or simulation approaches. The separation distance was found to have a piecewise linear relationship with capacity, while exiting flows had a linear positive relationship which becomes negative as the inhibitory effect increased at low separation distances. The two main mechanisms explaining these effects of exiting flows were the inhibitory mechanism (caused by drivers unable to distinguish between circulating and exiting vehicles), and changes in circulating headways. A revised empirical model incorporating this piecewise relationship performed as well as the exponential-in- Qc and linear-in-Qc models, suggesting that the impacts of exiting flows were modelled reasonably well. By improving our understanding of the impacts of these two variables on capacity, this is an important step towards the improved modelling of roundabout entry capacity.

APA, Harvard, Vancouver, ISO, and other styles

26

Wong, Ka-fu Katherine, and 黃家芙. "Roundabout transformation: 3D parkconnector." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31987321.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Elias, Aaron. "Roundabout modeling in CORSIM." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025029.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Souza, Johnny Vieira de. "Segurança de pedestres em rotatórias urbanas." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/4393.

Full text

Abstract:

Made available in DSpace on 2016-06-02T20:01:00Z (GMT). No. of bitstreams: 1 6766.pdf: 29436615 bytes, checksum: b6add30cfef1455d7033acb6e81e37d0 (MD5) Previous issue date: 2015-04-30
The Traffic and Transport Engineering has developed several techniques to mitigate the pernicious causes from the risks associated with intersections or crossing points level in traffic. Among the several devices of better efficiency and lower cost are the roundabouts, which are intended to simplify the intersection, so that the traffic that interacts there has a safe conduct, with few points of conflict and small delays. Although today has been widely used in the world and brazilian urban traffic the roundabouts are geometric elements that prioritize or monopolize motorized vehicular traffic due to lack of infrastructure, whether by choice or lack of technical knowledge, for cyclists, pedestrians and public transport have equal security. To assess what are the indicators that lead to this monopolization of devices were used ten roundabouts, being five in São José do Rio Preto and five in San Carlos, and proposed a confrontation of technical concepts between experts in the fields of Urban Planning and Urban Engineering, through AHP method, specialized literature and reality found in loco, to check for possible similarities and diferences existing between definitions, concepts and options and thus identify which factors are taken into consideration in the project, implementation and maintenance of or devices. Came to the conclusion that the specialized literature and subject matter experts defend pedestrians as a priority for the project, deployment, infrastructure and maintenance, but the devices are not able to safety.
A Engenharia de Tráfego e de Transportes tem desenvolvido várias técnicas para abrandar as causas perniciosas provenientes dos riscos existentes em pontos de interseção em nível no trânsito. Dentre os dispositivos viários de melhor eficiência e menor custo estão as rotatórias, que têm como finalidade simplificar a interseção, para que o tráfego que se ali interage tenha um desenrolar seguro, com poucos pontos de conflitos e pequenos tempos de espera. Embora na atualidade venha sendo muito utilizada no trânsito urbano mundial e brasileiro, as rotatórias são elementos geométricos que priorizam ou monopolizam o trânsito veicular motorizado devido à falta de infraestrutura, seja por opção ou carência de conhecimento técnico, para que ciclistas, pedestres, e transportes coletivos tenham igual segurança. Para aferir quais são os indicadores que levam a esta monopolização nos dispositivos, foram utilizados dez rotatórias sendo, cinco em São José do Rio Preto e cinco em São Carlos e proposto um confronto de conceitos técnicos entre especialistas nas áreas de Urbanismo e Engenharia Urbana, através do método AHP (Análise Hierárquica de Processos), literatura especializada e realidade constatada in loco, para verificar possíveis similaridades e diferenças existentes entre definições, conceitos e opções e assim identificar quais fatores são levados em consideração no projeto, implantação e ou manutenção dos dispositivos. Chegou-se à conclusão que a literatura especializada e os especialistas no assunto defendem os pedestres como prioridade para projeto, implantação, infraestrutura e manutenção, entretanto os dispositivos não estão aptos a segurança dos mesmos.

APA, Harvard, Vancouver, ISO, and other styles

29

Wong, Ka-fu Katherine. "Roundabout transformation 3D park connector /." Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B31987321.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Shukurov, Nadir. "Geometrical Design of Turbo Roundabout." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23336/.

Full text

Abstract:

The Turbo Roundabout is a roundabout fitted with spiral roads to efficiently counteract the complexities of the modern multilane roundabout. This roundabout has an edge over cutting-edge roundabouts regarding capacity and safety and was first invented by Professor Fortujin in 1996. Fast driving speeds and many possible conflicts at multilane roundabout approaches, exits and circulatory roadways are the reasons for this type of construction project. Road designers have been attempting to address these issues over the past few years by implementing new roundabout configurations. Turbo-roundabouts have also spread outside of the Netherlands over the last decade, mainly in Eastern Europe and Germany, but also in North America. While the Dutch model for turbo-roundabout design was strictly applied by some nations, others designed them on experimental sites, resulting in geometrical variations unique to the area. We have more than 390 turbo-roundabouts worldwide today. In this paper, the measurement of sight distance on turbo roundabouts with an emphasis on “Intersection Sight Distance” to conflicting vehicle circulation will be studied. The traditional graphical approach has been supplemented with the analytical solution consisting of derivation of generalized mathematical equations for intersection sight distance for conflicting circulating vehicle at turbo roundabout. To determine the design of turbo roundabout instead of standard type we collected numbers, iterations, flow rate and other information from the intersection in Neapol street - M.Hadi-Ashig Alaskar and Vungtau streets in the capital of Azerbaijan, Baku city. The current name of circle is “Ukraine circle” on behalf of friendship between Azerbaijan and Ukraine. Some of these collected specimens were used to perform the by using the software test at the University of Bologna and in Baku Transportation Agency by PTV VISSIM simulation and AutoCAD Civil.

APA, Harvard, Vancouver, ISO, and other styles

31

Septarina, Septarina. "Micro-Simulation of the Roundabout at Idrottsparken Using Aimsun : A Case Study of Idrottsparken Roundabout in Norrköping, Sweden." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-79964.

Full text

Abstract:

Microscopic traffic simulation is useful tool in analysing traffic and estimating the capacity and level of service of road networks. In this thesis, the four legged Idrottsparken roundabout in the city of Norrkoping in Sweden is analysed by using the microscopic traffic simulation package AIMSUN. For this purpose, data regarding traffic flow counts, travel times and queue lengths were collected for three consecutive weekdays during both the morning and afternoon peak periods. The data were then used in model building for simulation of traffic of the roundabout. The Root Mean Square Error (RMSE) method is used to get the optimal parameter value between queue length and travel time data and validation of travel time data are carried out to obtain the basic model which represents the existing condition of the system. Afterward, the results of the new models were evaluated and compared to the results of a SUMO model for the same scenario model. Based on calibrated and validated model, three alternative scenarios were simulated and analysed to improve efficiency of traffic network in the roundabout. The three scenarios includes: (1) add one free right turn in the north and east sections; (2) add one free right turn in the east and south sections; and (3) addition of one lane in roundabout. The analysis of these scenarios shows that the first and second scenario are only able to reduce the queue length and travel time in two or three legs, while the third scenario is not able to improve the performance of the roundabout. In this research, it can be concluded that the first scenario is considered as the best scenario compared to the second scenario and the third scenario. The comparison between AIMSUN and SUMO for the same scenario shows that the results have no significance differences. In calibration process, to get the optimal parameter values between the model measurements and the field measurements, both of AIMSUN and SUMO uses two significantly influencing parametersfor queue and travel time. AIMSUN package uses parameter of driver reaction time and the maximum acceleration, while SUMO package uses parameter of driver imperfection and also the driver rection time.

APA, Harvard, Vancouver, ISO, and other styles

32

Andre, Maud. "Expression and functional studies of roundabout 4." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:da66b7e3-617c-4fba-8d1e-d3169adc9812.

Full text

Abstract:

Roundabout (Robo) receptors were first identified in neurons as guidance molecules, however growing evidence suggests that they also play a role in other cells. The aim of this thesis was to characterise the expression and function of a novel endothelial specific member of this family, Robo4. This study revealed that Robo4 is expressed primarily in vessels but also differentially expressed in tumour vessels. Interestingly Robo4 was primarily located within cytoplasmic vesicles coated with clathrin, suggesting that the presence of Robo4 on the cell surface is being tightly regulated. Overexpression of Robo4 induced filopodia and pseudopodia formation and actin re-organisation into stress fibres. It co-localised with actin and tubulin suggesting an important interaction between Robo4 and the cytoskeleton. Robo4's function in endothelial cells was directly investigated using two approaches, overexpression using adenovirus and knockdown using small interfering RNA. Functional cell-based assays revealed that disrupting Robo4's level of expression negatively affects endothelial cell functions that are required during angiogenesis, such as proliferation, migration and tubulogenesis. Overexpression of a truncated version of Robo4, which lacks the C-terminus, provided clues regarding Robo4's function. The intracellular domain is critical for Robo4's localisation and its association with the cytoskeleton. It is also required for pseudopodia formation. Other findings include possible cleavage of Robo4 and Robo4 homodimerisation and heterodimerisation with Robo1. Taken together, the findings presented in this study strongly suggest a role for Robo4 in endothelial cell guidance. Cell guidance during angiogenesis is poorly understood therefore the identification of a new molecule potentially involved in this mechanism will hopefully help elucidate the process.

APA, Harvard, Vancouver, ISO, and other styles

33

Bisiak, Francesco. "Structural studies of the Roundabout protein family." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAV006/document.

Full text

Abstract:

Les systèmes neuronaux et vasculaires nécessitent un réseau complexe pour exécuter correctement leurs fonctions. Les processus impliqués dans la création de ce réseau s'appuient sur des voies coordonnées, souvent activées par des systèmes protéine/récepteur communs, qui conduisent au remodelage du cytosquelette.En général, les cellules neuronales et vasculaires répondent aux stimuli extracellulaires sous forme de protéines solubles sécrétées, qui interagissent avec les récepteurs de surface pour favoriser l'attraction ou la répulsion vers la source des protéines sécrétées. Ce processus, appelé guidage, est régulé par sept familles de récepteurs et leurs ligands respectifs, qui s'influencent les uns sur les autres et peuvent agir sur le système neuronal, le système vasculaire ou les deux ensembles.Cette étude est centrée sur deux récepteurs transmembranaires à passage unique, les membres des familles de protéines Roundabout et UNC5 qui sont principalement impliquées dans l'angiogenèse: Robo4 et UNC5B.L'information structurelle sur la région extracellulaire de plusieurs de ces récepteurs, et comment le signal est relayé à travers la membrane, fait défaut.La déglycosylation enzymatique a confirmé que les domaines extracellulaires de Robo4 et UNC5B sont largement glycosylés avec des glycanes liés en azote du complexe type. La mutagenèse dirigée des sites de glycosylation prédits de Robo4 perturbe son expression, indiquant que ces résidus sont nécessaires pour la stabilité de la protéine et que leur glycosylation, ou leur passage dans la voie de glycosylation, pourrait être nécessaire pour un repliement correct. Les données MALS et SAXS montrent qu'en solution, Robo4 ecto est un monomère flexible de forme allongée. Les domaines ne présentent pas des caractéristiques distinctes dans le modèle construit à partir des données SAXS. Plusieurs Fabs se liant au domaine extracellulaire de Robo4 ont été caractérisés, avec l'espoir d'identifier les Fab qui pourraient inhiber l'interaction Robo4 / UNC5B rapportée pour une caractérisation plus poussée. La formation du complexe a été vérifiée par SEC-MALS et SAXS, et les constantes d'interaction ont été déterminées en utilisant SPR. Des cristaux de certains complexes domaine Fab / domaine extracellulaire Robo4 ont été produits, bien que la structure du complexe n'ait pas pu être résolue à l'heure actuelle.Les expériences de pull-down, SEC-MALS et SPR montrent que Robo4 ecto et UNC5B ecto n'interagissent pas entre elles, malgré une étude par un autre groupe montrant le contraire. Étant donné que différentes lignées cellulaires ont été utilisées, des modèles de glycosylation spécifiques, ou une tierce partie non détectée, pourraient être nécessaires pour l'interaction. En raison de leur implication avec les récepteurs extracellulaires, les héparanes sulfates sont un candidat probable, mais d'autres partenaires devraient être envisagés.La structure cristallographique de l'UNC5B ecto est similaire aux structures existantes de UNC5A et UNC5D. Le haut degré de conservation des domaines del’Ig pourrait être une indication de l'importance de cette région, qui est responsable de la liaison à Netrin. Bien que la région de liaison de Netrin soit connue pour être dans les domaines Ig, le site de liaison précis n'a pas encore été déterminé, mais il pourrait être situé à proximité ou à l'intérieur des surfaces chargées négativement présentes sur les domaines Ig observées dans la structure d’UNC5B.Le travail présenté ici devrait servir de base à une meilleure caractérisation biochimique et structurale des récepteurs extracellulaires Robo4 et UNC5B
Neuronal and vascular systems require a complex network to properly perform their functions. The processes involved in creating this network rely on coordinated pathways, often activated through common protein/receptor systems, which lead to cytoskeletal remodelling. In general, neuronal and vascular cells respond to extracellular stimuli in the form of soluble secreted proteins, which interact with surface receptors to mediate attraction or repulsion towards the source of the secreted proteins. This process, called guidance, is regulated by seven families of receptors and their respective ligands, which influence each other and can act on the neuronal system, the vascular system or both.Structural information about the extracellular region of many of these receptors, and how signal is relayed across the membrane, is lacking.This study is focused around the extracellular domain of two single-pass transmembrane receptors of the Roundabout and UNC5 protein families that are majorly involved in angiogenesis: Robo4 and UNC5B.Based on the findings of this study, the Robo4 and UNC5B extracellular domains are extensively glycosylated with N-linked glycans of the complex type. Site-directed mutagenesis of the predicted Robo4 glycosylation sites disrupts protein expression, indicating that they are necessary for protein stability and passage through the glycosylation pathway might be necessary for correct folding. MALS and SAXS data show that in solution the Robo4 extracellular domain is a flexible monomer with extended shape. Several Fabs binding to the extracellular domain of Robo4 were characterised, with the expectation to identify those Fabs that could inhibit the reported Robo4/UNC5B interaction for further characterisation. Complex formation was verified by SEC-MALS and SAXS, and interaction constants were determined using SPR. Crystals of some Robo4 extracellular domain/Fab complexes were produced, although the structure of the complex could not be solved at the present time.Despite a study by another group showing otherwise, pull-down, SEC-MALS and SPR experiments show that the Robo4 and UNC5B extracellular domains do not interact with each other. It is proposed that the difference may be caused by different glycosylation patterns specific to the cell lines used for each study, or by an undetected third party necessary for interaction. This, however, still requires further study. SEC-MALS analysis showed that the UNC5B extracellular domain is a monomer in solution and its crystal structure was solved at 3.4 Å resolution. Comparison to the existing structures of human UNC5A and rat UNC5D shows striking similarities and a high degree of evolutionary conservation of the Ig domains might be indication of the importance of this region, which is responsible for binding to the guidance cue Netrin. Although the Netrin binding region is known to be within the Ig domains, the precise binding site has not yet been determined, but it might be located in proximity, or within, the negatively charged surfaces present on the Ig domains which are observed in the UNC5B structure.It is hoped that the work presented here will give the basis for better biochemical and structural characterisation of these two receptors

APA, Harvard, Vancouver, ISO, and other styles

34

Arndt, Owen. "Relationship between roundabout geometry and accident rates." Thesis, Queensland University of Technology, 1994.

Find full text

Abstract:

The aim of this research is to determine the effect of unsignalised intersection geometry on the rates of the various types of accidents occurring at unsignalised intersections. A literature review has identified that there is little consistency between the results of previous studies. Some studies found that particular parameters had an opposite effect to what was expected. With this in mind, the research identified reasons for these results and developed two basic approaches to mitigate some of the problems with multi-factor type studies. These approaches are 'maximise the efficiency of data collection' and 'develop techniques for analysing less than perfect data'. A database consisting of 206 unsignalised intersection sites from throughout Queensland was used for analysis. The outcome of this research confirms the validity of several of the current design standards for unsignalised intersections, in addition to identifying new engineering procedures.

APA, Harvard, Vancouver, ISO, and other styles

35

Heal, Paul. "Functional characterisation of a novel endothelial specific roundabout." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442761.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Bhatta, Pallavi. "Biochemical Studies of Roundabout Receptor Oligomerisation and Signalling." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520868.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Perez, Vargas Daniela Michelle, and Baltazar Jorge Enrique Yauyo. "Replanteo físico y operacional de la rotonda monitor ubicada en el distrito de Santiago de Surco para mejorar su eficiencia y seguridad vial." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/653423.

Full text

Abstract:

La investigación presenta un nuevo diseño de rotondas llamado turbo rotondas, estos tipos de rotondas se adoptan, debido a que las glorietas convencionales multicarril se encuentran relacionadas con problemas como lo son el comportamiento de los conductores en la entrada, carril circulatorio y zonas de salida de la rotonda; donde se observa el cambio e invasión de los carriles sin respetar las marcas divisorias de carril lo que genera mayor velocidad. Las turbo rotondas a comparación de las rotondas convencionales, poseen beneficios operativos y de seguridad, gracias a que tienen separadores de carril cuya principal función es de restringir los cambios de carril o malas maniobras de los conductores, reducir la velocidad y los puntos de conflictos. Para el caso de estudio se eligió a la rotonda Monitor por la congestión vehicular que presenta, la mala operación de la rotonda y la alta tasa de accidentes de tránsito, por lo que se plantea un rediseño físico y operacional mediante una turbo rotonda, donde se evaluará los niveles de servicio, las demoras y el nivel de seguridad a través de una microsimulación mediante el software Vissim 9 entre la rotonda actual y la propuesta. Finalmente, después de realizar varias corridas al programa se llega a la conclusión de que el replanteo físico y operacional de la rotonda Monitor Huáscar, a través de la Turbo Rotonda tipo rotor beneficia a los usuarios mejorando el nivel de servicio de F a C. Esto quiere decir, que las demoras y los tiempos de viaje se reducen significativamente. Además, de mejorar la seguridad vial reduciendo el número de puntos de conflicto.
The research presents a new roundabout design called turbo roundabouts, these types of roundabouts are adopted, due to specific multi-lane roundabouts are related to problems such as the behavior of drivers at the entrance, circulatory lane and exit areas of the roundabout where the change and invasion of the lanes is observed without respect the lane divisions marks which generates greater speed. The turbo roundabouts to the comparison of compact roundabouts, the features operational and safety benefits, thanks to the fact that they have rail separators whose main function is restricted lane changes or bad driver jaws, reduce speed and conflict points . In the case of the study, the roundabout Monitor was chosen because of the traffic congestion that shows inefficiency in the operation of the roundabout and high traffic accident rate, so a physical and operational redesign is proposed through a turbo roundabout, where it is evaluated service levels, delays and security level through microsimulation using Vissim 9 software between the current roundabout and the proposed one. Finally, after making several runs to the program, it is concluded that the physical and operational replacement of the Huáscar Monitor roundabout, through the Rotor-type Turbo Roundabout, benefits users by improving the service level from F to C. This wants That is, delays and travel times are significantly reduced. In addition, improve road safety by reducing the number of conflict points.
Tesis

APA, Harvard, Vancouver, ISO, and other styles

38

Pochowski, Alek L. "An analytical review of statewide roundabout programs and policies." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37285.

Full text

Abstract:

As the modern roundabout continues to grow in popularity within the United States, more states are considering or implementing statewide roundabout programs and policies. To assist states with the implementation of statewide roundabout programs and policies, an analytical review of statewide roundabout programs and policies was conducted through an examination of literature, interviews, and data pertaining to the construction of roundabouts. The roundabout policy type for each state and the District of Columbia was located, and assigned to a roundabout policy type based on the strength of the identified policy type. In addition, a series of per capita analyses of the statewide roundabout policies was performed, as was a qualitative SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis. The results of the analysis show that the strength of a statewide roundabout policy is correlated to the number of roundabouts in a state, and states should consider implementing or strengthening their policies if they seek to expand the use of roundabouts in their jurisdiction. In addition, the perception of roundabouts, both by the general public and internal to the state DOTs, also continues to hinder the further implementation of roundabouts, and education should be utilized to minimize these obstacles. Furthermore, states should utilize identified successful implementation procedures, and should be cognizant of reasons for implementation failure, as they pursue the further use of roundabouts by their agency.

APA, Harvard, Vancouver, ISO, and other styles

39

Kamla, Jwan Jameel Shekh Mohammed. "Analysing truck position data to study roundabout accident risk." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/37386/.

Full text

Abstract:

In order to reduce accident risk, highway authorities prioritise maintenance budgets partly based upon previous accident history. However, as accident rates have continued to fall in most contexts, this approach has become problematic as accident ‘black spots’ have been treated and the number of accidents at any individual site has fallen. Another way of identifying sites of higher accident risk might be to identify near-miss accidents (where an accident nearly happened, but was avoided), which are likely to be much more prolific than actual accidents, therefore they are useful in identifying high-risk sites. The principal aim of this research is to analyse potentially unsafe truck driving conditions that involving harsh braking incidents (HBIs) that may indicate accident risk. Most modern truck fleets now record position as part of fleet management. This research used position data collected by a truck fleet management company for 8000 trucks in the United Kingdom (UK) over a 2-year period (2011-2012) to identify incidents of harsh braking. This data was compared with STATS19 accident data events (specifically truck accidents) occurring in 70 selected roundabouts (284 approaches) over an 11-year period (2002-2012), to test the hypothesis that the HBIs could represent accident near-misses and therefore increased accident risk. The data used for model prediction comprised all vehicle accidents, truck accidents, HBIs, geometric properties, and traffic characteristics for whole roundabouts, within the circulatory lanes, and at approaches to the selected roundabouts. Random-parameters negative binomial (NB) count data models were used to estimate model parameters and the models were compared with fixed-parameters NB count data models. It was found that random-parameters count data models provide better goodness of fit and more variables were found to be significant, giving a better prediction of events. It is concluded that HBIs are influenced by traffic and geometric variables in a similar way to total and truck accidents, therefore they may be useful in considering accident risk at roundabouts. They are a source of higher volumes of data than accidents, which is important in considering changes or trends in accident risk over a much shorter time. The most important variables were Average Annual Daily Traffic (AADT) and percentage of truck traffic, which were found to have a positive influence on accidents and HBIs. Regarding the geometric variables, signalisation, circulatory roadway width, number of arms and two-lane indicator were the most important factors influencing accidents and HBIs. In addition to these models, numbers of HBIs was used as an independent variable in the models of total and truck accidents, along with traffic and geometric variables. From the results it can be concluded that at all approaches, HBIs are related to total accidents along with traffic and geometric variables, which can be used to study safety measures. A good predictive model for truck accidents at M-class approaches based on HBI, traffic and geometric parameters was identified that can be used for prioritising safety at these approaches in order to make roundabouts safer. For A- and B-class approaches a better fit model were identified when HBI were used as input variable along with traffic and geometric variables compared to the model without using HBI as input variable, but the influence of HBIs was negative (high HBIs with low numbers of accidents) which is probably an indicator of future accident risk in these locations. For at-grade roundabouts, a better fit model was obtained for total and truck accidents when it is compared to the model without HBIs, but the influence of HBIs was negative; this is probably an indicator of high accident risks in these at-grade roundabouts, however further investigation is required with more observations. These results for truck HBIs could help highway authorities to identify sites of increased accident risk more rapidly and without waiting for an accident history to develop.

APA, Harvard, Vancouver, ISO, and other styles

40

Sadeq, Haytham. "Automated roundabout safety analysis : diagnosis and remedy of safety problems." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44032.

Full text

Abstract:

The safety of a transportation system is a serious concern for transportation agencies and analysts. In Canada, roughly 29% and 43% of fatalities and serious injury collisions, respectively, occur at intersections (Road Safety Directorate, 2007). There has been a growing interest in the construction of roundabouts to improve the safety performance and increase the traffic efficiency at regular intersections. As more roundabouts are installed throughout North America, there will be an increased need for a detailed analysis of their safety performance. Collision data used to evaluate the safety performance of roundabouts is considered a reactive and costly approach. Recently, the Traffic Conflict Technique (TCT) has been used to improve and complement the collision-based safety diagnosis approach. The purpose of this thesis is to demonstrate the use of an automated safety analysis tool, developed at the University of British Columbia (UBC), for the diagnosis of safety issues at roundabouts. Traffic conflicts occurring at a roundabout, located at UBC campus, are automatically identified and analyzed to develop an in-depth understanding of the behaviour of road users and the causes of traffic conflicts. The results from this detailed and low-cost approach are used to propose effective countermeasures to proactively improve the safety of roundabouts, and to ultimately reduce collisions. Based on these results, the following safety concerns have been determined; a confusion of the right-of-way between entering and circulating vehicles; inappropriate negotiation between circulating and exiting vehicles; higher risk of pedestrian-vehicle conflicts at exit lanes than entry lanes and the accommodation of cyclists at mixed traffic roundabouts. Several countermeasures proposed to address these concerns are to add cross hatch markings, narrow down circulating lanes, modify central island markings, provide pedestrian crossing signs, and propose further education for drivers on using roundabouts and accommodating vulnerable road users. This thesis helps to demonstrate the effectiveness of the advanced safety tool in diagnosing safety, and proactively demonstrate safety issues at the roundabout.

APA, Harvard, Vancouver, ISO, and other styles

41

Ibragimova, S. B. "Influence of physical activity on development of the roundabout course." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/54753.

Full text

Abstract:

Introduction. Walls of veins of a wide fastion of a hip are much thicker at the expense of well developed external cover. Muscular veins have no such powerful external cover, they well developed a muscular layer. Veins are characterized by well developed muscular layer and an elastic framework.

APA, Harvard, Vancouver, ISO, and other styles

42

Barry, Christina Danielle. "Calibration of the hcm 2010 roundabout capacity equations for georgia conditions." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44887.

Full text

Abstract:

There is increased interest in building modern roundabouts in Georgia and in the United States because of the safety and operational benefits that can be realized from this type of intersection. With this interest comes the increasing need to be able to estimate the capacity that a roundabout can provide after it is built. In the early 2000s, a National Cooperative Highway Research Program (NCHRP) study was conducted that, among other tasks, developed single-lane and multi-lane roundabout capacity estimation equations. These equations, presented in the Highway Capacity Manual 2010 (HCM 2010), can be calibrated using locally determined values of follow-up headway and critical headway. This study was designed to calibrate the HCM 2010 roundabout capacity equation for single-lane roundabouts to driving conditions in Georgia. In order to develop estimates of the calibration parameters, video imagery was recorded for 13 approaches at six roundabouts in Georgia for approximately two hours during the peak period. A total of 29.5 hours of video was recorded. Data from three of these roundabouts forms the basis of this thesis. The videos were processed by a Java program to collect time stamps that were subsequently used in Microsoft Excel to calculate the follow-up and critical headway values required for calibration. The values of critical headway and follow-up headway that were found from the video data are presented in the results as well as the single-lane capacity equations calibrated from the data. Two types of analysis were done, one that includes exiting vehicles and one that does not include exiting vehicles. When exiting vehicles were excluded, the weighted average of follow-up and critical headway were found to be 3.46 and 4.17 seconds respectively and when exiting vehicles were included in the analysis the weighted averages of the follow-up and critical headway were found to be 2.80 seconds and 3.34 seconds respectively. It was found that exiting vehicles do have an impact on the operations at the roundabout in most cases, and including exiting vehicles in the analysis tends to increase the capacity predicted by the calibrated equations.

APA, Harvard, Vancouver, ISO, and other styles

43

Leksono, Catur Yudo, and Tina Andriyana. "Roundabout Microsimulation using SUMO : A Case Study in Idrottsparken RoundaboutNorrkӧping, Sweden." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-79771.

Full text

Abstract:

Idrottsparken roundabout in Norrkoping is located in the more dense part of the city.Congestion occurs in peak hours causing queue and extended travel time. This thesis aims to provide alternative model to reduce queue and travel time. Types ofobservation data are flow, length of queue, and travel time that are observed during peakhours in the morning and afternoon. Calibration process is done by minimising root meansquare error of queue, travel time, and combination both of them between observation andcalibrated model. SUMO version 0.14.0 is used to perform the microsimulation. There are two proposed alternatives, namely Scenario 1: the additional lane for right turnfrom East leg to North and from North leg to West and Scenario 2: restriction of heavy goodsvehicles passing Kungsgatan which is located in Northern leg of Idrottsparken roundaboutduring peak hours. For Scenario 1, the results from SUMO will be compared with AIMSUNin terms of queue and travel time. The result of microsimulation shows that parameters that have big influence in the calibrationprocess for SUMO are driver imperfection and driver’s reaction time, while for AIMSUN isdriver’s reaction time and maximum acceleration. From analysis found that the model of thecurrent situation at Idrottsparken can be represented by model simulation which usingcombination between root mean square error of queue and travel time in calibration andvalidation process. Moreover, scenario 2 is the best alternative for SUMO because itproduces the decrease of queue and travel time almost in all legs at morning and afternoonpeak hour without accompanied by increase significant value of them in the other legs. Thecomparison between SUMO and AIMSUN shows that, in general, the AIMSUN has higherchanges value in terms of queue and travel time due to the limited precision in SUMO forroundabout modelling.

APA, Harvard, Vancouver, ISO, and other styles

44

Abdul, Jabbar Jalal Aldeen Abdul. "An evaluation of pelican crossings on roundabout approaches in urban areas." Thesis, Cardiff University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321882.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Sullivan, Daniel P. "Vehicle headway and lane flow distributions on multi-lane arterial roads." Thesis, Queensland University of Technology, 2001.

Find full text

APA, Harvard, Vancouver, ISO, and other styles

46

Fong, Pui San. "Assessment of roundabout in urban road network :a case study of Macau." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691706.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Annam, Raja Bharat. "Synthetic Innovation to Complex Intersection Control: Intelligent Roundabout in Connected Vehicle Environment." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623169949508287.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Schmitt, Laura E. "Calibration of the HCM 2010 single-lane roundabout capacity equations for Georgia conditions (Phase 2)." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50413.

Full text

Abstract:

The operational performance of an existing or proposed roundabout can be assessed through capacity models. In order to provide improved capacity predictions for existing and proposed Georgia roundabouts, the 2010 HCM roundabout capacity equations need to be locally calibrated based on Georgia drivers. The purpose of this study is to collect field data necessary to calculate follow-up and critical headways at Georgia roundabouts in order to calibrate the 2010 HCM capacity equations to yield improved capacity predictions. The research team filmed 28 approaches at thirteen Georgia roundabouts for a total of 56.5 hours. The video was processed manually using an in-house computer program. Based on analyst keystrokes during the video review the program would extract timestamps of events that are necessary for calculating follow-up and critical headway. The follow-up and critical headway values were calculated for two different data sets: 1) including exiting vehicles and 2) excluding exiting vehicles. The critical and follow-up headway for an analysis including exiting vehicles is 4.192 seconds and 2.788 seconds respectively. The critical and follow-up headway for an analysis excluding exiting vehicles is 4.747 seconds and 3.265 seconds respectively. This study found that including the exiting vehicles impacts the capacity. The capacity increases or decreases based on the percentage of conflicting vehicles that are exiting vehicles. In addition, this study’s calibrated model excluding exiting vehicles predicts higher capacity than the 2010 HCM model that GDOT recommends which also excludes exiting vehicles.

APA, Harvard, Vancouver, ISO, and other styles

49

Giddings, David Roger. "A probabilistic model for the movement of traffic through a small roundabout using discrete time units." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387416.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Perkins, Bethany. ""In a roundabout way" evasive, oblique and indirect discourse in Allen Tate, Tennessee Williams and Lewis Nordan /." Greensboro, N.C. : University of North Carolina at Greensboro, 2007. http://libres.uncg.edu/edocs/etd/1494Perkins/umi-uncg-1494.pdf.

Full text

Abstract:

Thesis (Ph.D.)--University of North Carolina at Greensboro, 2007.
Title from PDF t.p. (viewed Mar. 3, 2008). Directed by Scott Romine; submitted to the Dept. of English. Includes bibliographical references (p. 203-214).

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Roundabouts'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles