Abstract: Traffic congestion is the most critical issue faced by those in the transportation profession today. Over the past few years, roundabouts have been recognized as a measure to promote efficiency at intersections globally. In developing countries like India, this type of intersection still faces a lot of issues, such as bottleneck situations, long queues and increased waiting times, due to increasing traffic which in turn affect the performance of the entire urban network. This research is a case study of a non-conventional roundabout, in terms of geometric design, in a small town in India. These types of roundabouts should be analyzed for their functionality in mixed traffic conditions, prevalent in many developing countries. Microscopic traffic simulation is an effective tool to analyze traffic conditions and estimate various measures of operational performance of intersections such as capacity, vehicle delay, queue length and Level of Service (LOS) of urban roadway network. This study involves analyzation of an unsymmetrical non-circular 6-legged roundabout known as “Kala Aam Chauraha” in a small town Bulandshahr in Uttar Pradesh, India using VISSIM simulation package which is the most widely used software for microscopic traffic simulation. For coding in VISSIM, data are collected from the site during morning and evening peak hours of a weekday and then analyzed for base model building. The model is calibrated on driving behavior and vehicle parameters and an optimal set of calibrated parameters is obtained followed by validation of the model to obtain the base model which can replicate the real field conditions. This calibrated and validated model is then used to analyze the prevailing operational traffic performance of the roundabout which is then compared with a proposed alternative to improve efficiency of roundabout network and to accommodate pedestrians in the geometry. The study results show that the alternative proposed is an advantage over the present roundabout as it considerably reduces congestion, vehicle delay and queue length and hence, successfully improves roundabout performance without compromising on pedestrian safety. The study proposes similar designs for modification of existing non-conventional roundabouts experiencing excessive delays and queues in order to improve their efficiency especially in the case of developing countries. From this study, it can be concluded that there is a need to improve the current geometry of such roundabouts to ensure better traffic performance and safety of drivers and pedestrians negotiating the intersection and hence this proposal may be considered as a best fit.
Abstract: This paper considers the modelling of a non-stationary
bivariate integer-valued autoregressive moving average of order
one (BINARMA(1,1)) with correlated Poisson innovations. The
BINARMA(1,1) model is specified using the binomial thinning
operator and by assuming that the cross-correlation between the
two series is induced by the innovation terms only. Based on
these assumptions, the non-stationary marginal and joint moments
of the BINARMA(1,1) are derived iteratively by using some initial
stationary moments. As regards to the estimation of parameters of
the proposed model, the conditional maximum likelihood (CML)
estimation method is derived based on thinning and convolution
properties. The forecasting equations of the BINARMA(1,1) model
are also derived. A simulation study is also proposed where
BINARMA(1,1) count data are generated using a multivariate
Poisson R code for the innovation terms. The performance of
the BINARMA(1,1) model is then assessed through a simulation
experiment and the mean estimates of the model parameters obtained
are all efficient, based on their standard errors. The proposed model
is then used to analyse a real-life accident data on the motorway in
Mauritius, based on some covariates: policemen, daily patrol, speed
cameras, traffic lights and roundabouts. The BINARMA(1,1) model
is applied on the accident data and the CML estimates clearly indicate
a significant impact of the covariates on the number of accidents on
the motorway in Mauritius. The forecasting equations also provide
reliable one-step ahead forecasts.
Abstract: Traffic accidents are a result of the convergence of hazards, malfunctioning of vehicles and human negligence that have adverse economic and health impacts and effects. Unfortunately, avoiding them completely is very difficult, but with quick response to rescue and first aid, the mortality rate of inflicted persons can be reduced significantly. Smart and innovative technologies can play a pivotal role to respond faster to traffic crash emergencies comparing conventional means of transportation. For instance, Rescue Emergency Drone (RED) can provide faster and real-time crash site risk assessment to emergency medical services, thereby helping them to quickly and accurately assess a situation, dispatch the right equipment and assist bystanders to treat inflicted person properly. To conduct a research in this regard, the case of a traffic roundabout that is prone to frequent traffic accidents on the outskirts of Esbjerg, a town located on western coast of Denmark is hypothetically considered. Along with manual calculations, Emergency Disaster Management Simulation (EDMSIM) has been used to verify the response time of RED from a fire station of the town to the presumed crash site. The results of the study demonstrate the robustness of RED into emergency services to help save lives.
Abstract: This work investigates a mathematical study for traffic flow and traffic density in Kigali city roads and the data collected from the national police of Rwanda in 2012. While working on this topic, some mathematical models were used in order to analyze and compare traffic variables. This work has been carried out on Kigali roads specifically at roundabouts from Kigali Business Center (KBC) to Prince House as our study sites. In this project, we used some mathematical tools to analyze the data collected and to understand the relationship between traffic variables. We applied the Poisson distribution method to analyze and to know the number of accidents occurred in this section of the road which is from KBC to Prince House. The results show that the accidents that occurred in 2012 were at very high rates due to the fact that this section has a very narrow single lane on each side which leads to high congestion of vehicles, and consequently, accidents occur very frequently. Using the data of speeds and densities collected from this section of road, we found that the increment of the density results in a decrement of the speed of the vehicle. At the point where the density is equal to the jam density the speed becomes zero. The approach is promising in capturing sudden changes on flow patterns and is open to be utilized in a series of intelligent management strategies and especially in noncurrent congestion effect detection and control.
Abstract: There is a call to ensure that the issues of safety and efficient throughput are considered during design; the solutions to these issues can also be retrofitted at locations where they were not captured during design, but have become problems to road users over time. This paper adopts several methods to analyze the performance of an intersection which was formerly a ‘priority-controlled’ intersection, but has now been converted to a ‘signal-controlled’ intersection. Extensive review of literature helped form the basis for result analysis and discussion. The Ikot-Ekpene/Anagha-Ezikpe intersection, located at the heart of Umuahia was adopted as case study; considering the high traffic volume on the route. Anecdotal evidence revealed that traffic signals imposed enormous delays at the intersection, especially for traffic on the major road. The major road has arrival flow which surpasses the saturation flow obtained from modelling of the isolated signalized intersection. Similarly, there were several geometric elements that did not agree with the specific function of the road. A roundabout, particularly flower roundabout was recommended as a better traffic control measure.
Abstract: The Haussmannization plan of Cairo in 1867 formed a
regular network of roundabout spaces, though deteriorated at present.
The method of identifying the spatial structure of roundabout Cairo
for conservation matches the voronoi diagram with the space syntax
through their geometrical property of spatial convexity. In this
initiative, the primary convex hull of first-order voronoi adopts the
integral and control measurements of space syntax on Cairo’s
roundabout generators. The functional essence of royal palaces
optimizes the roundabout structure in terms of spatial measurements
and the symbolic voronoi projection of 'Tahrir Roundabout' over the
Giza Nile and Pyramids. Some roundabouts of major public and
commercial landmarks surround the pole of 'Ezbekia Garden' with a
higher control than integral measurements, which filter the new
spatial structure from the adjacent traditional town. Nevertheless, the
least integral and control measures correspond to the voronoi
contents of pollutant workshops and the plateau of old Cairo Citadel
with the visual compensation of new royal landmarks on top.
Meanwhile, the extended suburbs of infinite voronoi polygons
arrange high control generators of chateaux housing in 'garden city'
environs. The point pattern of roundabouts determines the
geometrical characteristics of voronoi polygons. The measured
lengths of voronoi edges alternate between the zoned short range at
the new poles of Cairo and the distributed structure of longer range.
Nevertheless, the shortest range of generator-vertex geometry
concentrates at 'Ezbekia Garden' where the crossways of vast Cairo
intersect, which maximizes the variety of choice at different spatial
resolutions. However, the symbolic 'Hippodrome' which is the largest
public landmark forms exclusive geometrical measurements, while
structuring a most integrative roundabout to parallel the royal syntax.
Overview of the symbolic convex hull of voronoi with space syntax
interconnects Parisian Cairo with the spatial chronology of scattered
monuments to conceive one universal Cairo structure. Accordingly,
the approached methodology of 'voronoi-syntax' prospects the future
conservation of roundabout Cairo at the inferred city-level concept.
Abstract: This paper evaluates the performance of a multi-lane
four legged modern roundabout operating in Muscat using SIDRA
model. The performance measures include Degree of Saturation
(DOS), average delay, and queue lengths. The geometric and traffic
data were used for model preparation. Gap acceptance parameters,
critical gap and follow up headway, were used for calibration of
SIDRA model. The results from the analysis showed that currently
the roundabout is experiencing delays up to 610 seconds per vehicle
with DOS 1.67 during peak hour. Further, sensitivity analysis for
general and roundabout parameters was performed, amongst lane
width, cruise speed, inscribed diameter, entry radius and entry angle
showed that inscribed diameter is most crucial factor affecting delay
and DOS. Up gradation of roundabout to fully signalized junction
was found as the suitable solution which will serve for future years
with LOS C for design year having DOS of 0.9 with average control
delay of 51.9 seconds per vehicle.
Abstract: An efficient freeway system will be essential to the
development of Africa, and interchanges are a key to that efficiency.
Around the world, many interchanges between freeways and surface
streets, called service interchanges, are of the diamond configuration,
and interchanges using roundabouts or loop ramps are also popular.
However, many diamond interchanges have serious operational
problems, interchanges with roundabouts fail at high demand levels,
and loops use lots of expensive land. Newer service interchange
designs provide other options. The most popular new interchange
design in the US at the moment is the double crossover diamond
(DCD), also known as the diverging diamond. The DCD has
enormous potential, but also has several significant limitations.
The objectives of this paper are to review new service interchange
options and to highlight some of the main features of those
alternatives. The paper tests four conventional and seven
unconventional designs using seven measures related to efficiency,
cost, and safety.
The results show that there is no superior design in all measures
investigated. The DCD is better than most designs tested on most
measures examined. However, the DCD was only superior to all
other designs for bridge width. The DCD performed relatively poorly
for capacity and for serving pedestrians. Based on the results, African
freeway designers are encouraged to investigate the full range of
alternatives that could work at the spot of interest. Diamonds and
DCDs have their niches, but some of the other designs investigated
could be optimum at some spots.
Abstract: Roundabout work on the principle of circulation and
entry flows, where the maximum entry flow rates depend largely on
circulating flow bearing in mind that entry flows must give away to
circulating flows. Where an existing roundabout has a road hump
installed at the entry arm, it can be hypothesized that the kinematics
of vehicles may prevent the entry arm from achieving optimum
performance. Road humps are traffic calming devices placed across
road width solely as speed reduction mechanism. They are the
preferred traffic calming option in Malaysia and often used on single
and dual carriageway local routes. The speed limit on local routes is
30mph (50 km/hr). Road humps in their various forms achieved the
biggest mean speed reduction (based on a mean speed before traffic
calming of 30mph) of up to 10mph or 16 km/hr according to the UK
Department of Transport. The underlying aim of reduced speed
should be to achieve a 'safe' distribution of speeds which reflects the
function of the road and the impacts on the local community.
Constraining safe distribution of speeds may lead to poor drivers
timing and delayed reflex reaction that can probably cause accident.
Previous studies on road hump impact have focused mainly on speed
reduction, traffic volume, noise and vibrations, discomfort and delay
from the use of road humps. The paper is aimed at optimal entry and
circulating flow induced by road humps. Results show that
roundabout entry and circulating flow perform better in
circumstances where there is no road hump at entrance.
Abstract: KREISIG is a computer simulation program, firstly developed by Munawar (1994) in Germany to optimize signalized roundabout. The traffic movement is based on the car following theory. Turbine method has been implemented for signal setting. The program has then been further developed in Indonesia to meet the traffic characteristics in Indonesia by adjusting the sensitivity of the drivers. Trial and error method has been implemented to adjust the saturation flow. The saturation flow output has also been compared to the calculation method according to 1997 Indonesian Highway Capacity Manual. It has then been implemented to optimize signalized roundabout at Kleringan roundabout in Malioboro area, Yogyakarta, Indonesia. It is found that this method can optimize the signal setting of this roundabout. Therefore, it is recommended to use this program to optimize signalized roundabout.