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A Study On Feasible Traffic Operation Alternatives At Signalized Intersection In Dhaka City

Authors:
Anik Das at Atkins Global
Anik Das
Saurav Barua at Daffodil International University
Saurav Barua
Kamol Chandra Roy at CPCS Transcom Inc.
Kamol Chandra Roy
  • CPCS Transcom Inc.
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Abstract and Figures

At present, traffic congestion problem in Dhaka city is getting worse day by day. This is due to the huge amount of flow from side approaches, illegal car parking, mismanagement of traffic signal etc. The main aim of this investigation is to assess and develop the traffic operations at the Science Laboratory-Elephant Road signalized intersections in Dhaka city. This intersection is located in the busiest portion of Dhaka. The intersection has heavy traffic volume with higher delay and heavy traffic congestion compare to any other similar intersections in Dhaka. In this study, the intersection is analyzed as an isolated signalized intersection by using VISSIM simulation computer program. VISSIM computer program is also used for improvement through optimization process. The geometric, traffic and signalized data were collected during peak time periods. Four alternatives are recommended to solve the current and future problems. The recommended alternatives are—1. Banning right turning at all approaches (this alternative has already been implemented), 2. Optimization of the existing traffic signals, 3. Construct one through overpass for one direction and 4. Construct two overpasses for two directions. The first two alternatives will not be able to improve the level of service significantly. In contrast, the third and fourth alternative will improve the level of service with low delay time. The estimated initial cost of constructing two overpasses is more than annual saving. However, third alternative will be more cost effective and adequate to resolve traffic congestion problem of that location. If alternative three was selected to solve the existing situation; it will beneficial by reducing the congestion on the signalized intersection especially during peak hours, reducing the cost of traveling, increasing the efficiency of the road network, increasing safety, improving traffic flow and traffic operations, and reducing air pollution and preserving the environment.
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International Conference on Recent Innovation in Civil Engineering for Sustainable
Development (IICSD-2015)
Department of Civil Engineering
DUET - Gazipur, Bangladesh
A Study On Feasible Traffic Operation Alternatives At Signalized Intersection
In Dhaka City
K. C. Roy1*; S. Barua2; A. Das2
1Lecturer, Department of Civil Engineering
Stamford University Bangladesh, Dhaka – 1217, Bangladesh
2 Lecturer, Department of Civil Engineering
University of Information Technology and Science (UITS), Dhaka – 1212, Bangladesh
Abstract
At present, traffic congestion problem in Dhaka city is getting worse day by day. This is due to
the huge amount of flow from side approaches, illegal car parking, mismanagement of traffic
signal etc. The main aim of this investigation is to assess and develop the traffic operations at the
Science Laboratory-Elephant Road signalized intersections in Dhaka city. This intersection is
located in the busiest portion of Dhaka. The intersection has heavy traffic volume with higher
delay and heavy traffic congestion compare to any other similar intersections in Dhaka. In this
study, the intersection is analyzed as an isolated signalized intersection by using VISSIM
simulation computer program. VISSIM computer program is also used for improvement through
optimization process. The geometric, traffic and signalized data were collected during peak time
periods. Four alternatives are recommended to solve the current and future problems. The
recommended alternatives are—1. Banning right turning at all approaches (this alternative has
already been implemented), 2. Optimization of the existing traffic signals, 3. Construct one
through overpass for one direction and 4. Construct two overpasses for two directions. The first
two alternatives will not be able to improve the level of service significantly. In contrast, the third
and fourth alternative will improve the level of service with low delay time. The estimated initial
cost of constructing two overpasses is more than annual saving. However, third alternative will
be more cost effective and adequate to resolve traffic congestion problem of that location. If
alternative three was selected to solve the existing situation; it will beneficial by reducing the
congestion on the signalized intersection especially during peak hours, reducing the cost of
traveling, increasing the efficiency of the road network, increasing safety, improving traffic flow
and traffic operations, and reducing air pollution and preserving the environment.
Keywords: delay time, intersection, level of service, optimization, overpass, VISSIM.
1. Introduction
Dhaka is a city of 15 million population where traffic congestion is a common day-to-day
phenomena. Concerned Government agencies have taken several steps to alleviate congestion
problem. However, due to high traffic volume comparing to inadequate road cannot cope with
the solution. Most of the important intersections become source of major bottlenecks and cause
tremendous gridlock jam all along the adjacent downstream road sections. As a result, the
Paper ID: TE-004
whole road network suffers traffic congestion. Therefore, it would be more efficient to
consider these important intersections, thereby alleviate traffic congestion. Science
Laboratory- Elephant road intersection is one of the most important intersections in Dhaka
city. Traffic from Dhanmondi Residential area, New Market, Shahbagh and Farmgate are
coming into this intersection. Hence, it is vital to resolve traffic problem in this intersection to
alleviate traffic congestion in the whole Elephant road-New Market area. Several
comprehensive improvement alternatives are evaluated by the traffic simulation software
VISSIM; as it is a very practical and effective tool to evaluate the proposed traffic
improvement options in reducing traffic congestion.
2. Literature Review
Several methods are adopted by researchers to resolve traffic congestion problem in signalized
intersection. Meyer [1] suggested turn prohibition, signal improvement and arterial
management to alleviate traffic jam. A study conducted by Schrank and Lomax [2] have showed
that traffic signal coordination reduced delay at arterial road. Enustun [3] observed that
converting two way-street to one way will increase travel speed noticeably. Dixit [4] focused
on advantages of one-way street to reduce traffic collision. Meredith and Prem [5] identified
two way street would increase in vehicle hours-of-travel and potential for more accidents and
would decrease in vehicle miles-of-travel. Chaudhry et al. [6] developed guidelines to mitigate
congestion in traffic signal systems. Dbindsa and Spiller [7] evaluated that the recurring
localized bottlenecks occur when the approaching traffic rate exceeds the departing traffic rate
due to physical constraints. Lin et al. [8] showed that the traffic congestion at an intersection
can be reduced by an alternate route to bypass that intersection and reduce average delay
subsequently. VISSIM was used by several researchers to compare alternative design strategies
for traffic intersections and networks. It is a microscopic traffic simulation model developed at
the University of Karlsruhe, Karlsruhe, Germany, in the early 1970s. Leng et al. [9] evaluated
operational performance of U-turn at intersection using VISSIM. Lin and Yang [10] conducted
analysis of road network in the CBD of Beijing city. Gao et al. [11] conducted congestion
analysis and identification using VISSIM simulation. Siddharth and Ramadurai [12] worked on
effects of heterogeneous traffic mix in the intersection by VISSIM.
3. Study Area and Research Method
The study area of this research is to assess and develop the traffic operations at the Science
Laboratory-Elephant Road signalized intersections in Dhaka city shown in Figure 1. This
intersection is located in the busiest portion of Dhaka. The intersection has heavy traffic volume
with higher delay and heavy traffic congestion compare to any other similar intersections in
Dhaka.
Traffic volume data for each approach of the Science laboratory- Elephant road intersections
were collected. Manual traffic counts were conducted on the intersection to identify the peak
periods. It was found that all approaches had the same morning peak period; however, they had
different off peak noon and evening peak periods. So, it was decided to adopt the morning peak
period for the rest of the analysis.
Figure 1: Location of Science laboratory-Elephant road intersection
As well as, the volumes of turning and through movements in the intersection with vehicle
classifications were collected. The data were recorded during the morning peak period on
typical working days and all traffic are converted to passenger car equivalent (PCE) for the
study. The collected field data was used for the model calibration and validation. VISSIM
simulation software was used to model the existing road geometry and traffic condition. After
that, three other alternatives were taken into consideration to reduce traffic jam. One is
optimizing existing signal timing. Second one was constructing an overpass from New Market
to Kalabagan approach. In the last option, two over pass were constructed one in New Market
to Kalabagan approach and another one was Elephant road to Dhanmondi approach. However,
constructing two overpass were very expensive and less feasible considering the surrounding
infrastructure of the area. Therefore, third alternatives was discarded here for simplicity. Later,
comparative study was conducted based on average speed, average delay and average queue
length. Evaluating alternatives, the best alternative was selected and recommended.
4. Data Collection
The collected traffic data was for 15 minutes at 9:00-10:00 am. Figure-2 presents traffic volume
data along with flow direction. During field survey geometric data such as—the number of
lanes, lane widths and control data such as—signal timings, phasing were collected.
The selected study area consists of four approaches in the Science laboratory to Elephant road
intersection in Dhaka city. Four traffic signals are located in the intersection as followings: (1)
New Market to Kalabagan bound traffic, (2) Elephant road to Science laboratory bound traffic,
(3) Kalabagan to New Market bound traffic and (4) U-turn traffic. Figure 2 and 3 show the
modeling of the intersection on existing condition and VISSIM.
5. Data Analysis
First, existing condition in the intersection was modeled using VISSIM considering existing
signal timing. Figure 4 represents existing and optimized signal timing used in VISSIM
simulation. VISSIM produces several measures of effectiveness (MOE). The main MOEs
used in this study for comparing different alternative scenarios are— average speed, average
delay and average queue length. The proposed three alternative scenarios were analyzed and
each scenario was compared to the existing condition in traffic speed (increase), delay
(decrease) and queue length (decrease) in the Figure 5.
Figure-2(a): Traffic volume and flow
direction at Elephant road and Road#2
portion
Figure-2(b): Traffic volume and flow
direction at Science laboratory and Green road
portion
Figure-3(a): Science Laboratory- Elephant
road intersection in Google Map
Figure-3(b): VISSIM model of Science
Laboratory-Elephant road intersection
Figure 5(a):Comparative average speed
Figure 5(b): Comparative average delay
Figure 5(c): Comparative average queue length
Some percentage of increase in average traffic speed and reduction in intersection delay and
queue length had been obtained in the scenario 2 where traffic signals were optimized. Benefits
obtained by optimizing the traffic signals were 17.32% speed increase, average delay reduction
61.82% and 26.31% queue length reduction. It can be seen that the scenario of one overpass
was the best and provided the highest average traffic speed (250.6% increase as compared to
the existing condition) and lowest average queue length (92.91% reduction as compared to the
existing condition). Moreover, average delay reduces 100%. This is due to the signal free
intersection with only merging and diverging traffic conflicts. Therefore this study shows that
maximum benefits can be achieved by alternative scenario 3.
Figure-4(a): Existing signal timing in
VISSIM
Figure-4(b): Optimized signal timing in
VISSIM
6. Conclusion
The results of the intersection analysis showed that the best alternative is constructing one
overpass. In contrast, constructing two overpass requires high budget, long time and requisition
of large area comparing to the other alternatives. Therefore, scenario 3 is more feasible
considering all relevant issues. During peak hour traffic volume is very high. It has been
observed that optimizing traffic signal or adjusting existing signal timing can handle the large
traffic volume poorly. Therefore, signal optimization in the Science laboratory- Elephant road
intersection cannot be the best alternatives. Though some benefits could be obtained by
optimization of signals, while good designed one over pass might provide desired traffic
performance than signalized intersection.
References
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[3] N. Enustun, Study of the Operational Aspects of One-Way and Two-Way Streets. Report
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... The literature covers a wide variety of researches indicating that one of the effective methods to reduce traffic congestion and delay and improving the performance of signalized intersections is the optimization of signal timing (Sunkari, 2004;Siddiqui, 2015;Udomsilp, et al., 2017;Ratrout and Assi, 2019). Others found that appropriate intersection improvement alternatives to achieve efficient operations include changing traffic signal timing, introducing additional lanes, and modifying the geometric conditions (Nyantakyi, et al., 2013;Roy, Barua and Das, 2015;Al-Allaff, et al., 2015;Zhang, Sun and Kondyli, 2017;Ragab and Abo El-Naga, 2019). Although, the focus of this research is using Synchro software and highway capacity manual (HCM) 2010 calculations, the findings from past published studies related to the evaluation and optimization of traffic performance at signalized intersections involved using different optimization software. ...
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VISSIM-Based Simulation Approach to Evaluation of Design and Operational Performance of U-turn at Intersection in China
Article
  • Dec 2008
Right turn plus U-turn or U-turn plus right turn (RT+UT or UT+RT) at intersection as an alternative to direct left turn (DLT) has been considered as an important access management. As simulation tool, VISSIM has been widely used in German and other countries. However, VISSIM has been calibrated based on the Germany traffic characteristics, It has limitation to applying to China’s traffic conditions. The goal of this paper is to explore the applicability of VISSIM in simulating RT+UT in China.Three sites were singled out to do field data collection. The average delay and travel time were used as the measures of effectiveness in model calibration. The model parameters were calibrated based on the field data. Two different U-turn traffic control plans were designed and comparisons between DLT and RT+UT in terms of average delay and maximal queue length were conducted. The simulation results show that with perfect calibration VISSIM can be applied to simulate RT+UT at intersection of China. In addition, it is shown that the proper U-turn design may improve greatly the traffic operational performance.
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