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INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING
Volume 5, No 2, 2014
© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0
Research article ISSN 0976 – 4399
Received on September, 2014 Published on November 2014 144
The impacts of traffic signal timings optimization on reducing vehicle
emissions and fuel consumption by Aimsun and Synchro software's (Case
study: Tehran intersections) Ali Mansour Khaki1, Pegah jafari Haghighat Pour2
1-Associate Professor, Department of Civil Engineering, University of Science and
Technology, Tehran, Iran.
2- Ph.D Candidate in Transportation of Tehran Payame Noor University, Tehran, Iran
doi: 10.6088/ijcser.2014050014
ABSTRACT
Considering the fact that in recent years the transport sector allocated considerable fuel
consumption and emissions, evaluating issues related to fuel consumption and air pollution is
one of the most important issues of transport sector. Estimate of fuel consumption models
and emissions are new issues that discussions of various models have been published in Iran
and different countries. But assessing the impact of traffic signal timing optimization on fuel
consumption and emissions is one of the new and important subjects that have significant
effect on emissions and economics. Therefore, 5 Intersections of Tehran in 5 different areas
selected for the case study and studied period in traffic simulation and optimization to address
problems related to emissions were in 2013 in this thesis. Traffic data and parameters that
related to emissions and fuel consumption is obtained as ADT in days of October in studied
year. After optimization, the validity and accuracy of project have been used by Aimsun
software and it was observed that traffic signal timing optimization have significant reduction
in emissions and fuel consumption. The considerable results of this research can be cited to
Synchro software application in traffic signal timing optimization. For example, after
optimization fuel consumption has been decreased about 0.25%, 0.17% in AM peak time and,
3.63%, 2.46%, in PM peak time at Mahalati-10 farvardin, Shariati-Dolat intersections
respectively.
Keywords: Intersections, optimization, reduction in vehicle emissions and fuel consumption,
traffic signal timings.
1. Introduction
The transportation sector in Iran accounts for about 35% of total energy consumption and
nearly 70% of total oil consumption (Energy and Economic magazine). Heavy reliance on
fossil fuels might have accelerated climate change, and threatened energy security and public
health. Ever increasing concerns on energy and emissions have led the transportation sector
to mitigate the adverse impacts on vehicle emissions and fuel consumption.
It has been widely accepted that improving traffic flow has been one of the strategies to
reduce vehicle emissions and fuel consumption. In urban areas, frequent stop-and-go driving
and excessive speed variations contribute to higher fuel consumption and emissions. While
traffic signal timing optimization can reduce the number of stops and maintain moderate
vehicle speed, little is known of the impact of direct optimization for minimizing fuel
consumption or emissions, especially using a transportation planning-level microscopic
traffic simulator. Today, improving the flow of traffic is acceptable as one of the effective
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 145
Volume5 Issue2 2014
methods of reducing emissions and fuel consumption. Therefore other methods, such as
traffic management, timing optimization is important to reduce delays. High volume of
stopped vehicles without engine operation cause to waste large amount of fuel and emissions.
So traffic signal timing optimization by using simulation and optimization software at the
microscopic level transportation planning can make a direct impact to minimize fuel
consumption and emissions.The objective of this article is to quantify the impact of traffic
signal timing optimization on fuel consumption and emissions. The proposed method consists
of the combination as traffic simulation, timing optimization using the related software. Also
comparison of different software to select the best optimization method is done.
2. Literature review
L.Adacher has been provided the article, a global optimization approach to solve the traffic
signal synchronization problem. In this study investigates the Traffic Signal Synchronization
is a traffic engineering technique of matching the green light times for a series of
intersections to enable the maximum number of vehicles to pass through, thereby reducing
stops and delays experienced by motorists. Synchronizing traffic signals ensures a better flow
of traffic and minimizes gas consumption and pollutant emissions. The objective function
used in this work is a weighted sum of the delays caused by the signalized intersections. In
this paper, they apply generalized 'surrogate problem' methodology that is based on an on-
line control scheme which transforms the problem into a 'surrogate' continuous optimization
problem and proceeds to solve the latter using standard gradient-based approaches while
simultaneously updating both actual and surrogate system states. They extend a `surrogate
problem' approach that is developed for a class of stochastic discrete optimization problems
so as to tackle the traffic signal synchronization problem to minimize the total
delay .Numerical experiments conducted on a test and a real networks show that the surrogate
method converges in a very small area (Adacher L, 2012).
Li Jie, et al have been provided the article, Calibration of a microscopic simulation model for
emission calculation. In this article they indicated that Emissions by road traffic can be
reduced by optimizing traffic control. The impact of this optimization on emission can be
analyses by simulation. The simulation programs used for this analysis should be valid with
respect to the traffic characteristics that determine the emissions. Thus calibration of the
parameters is a prerequisite. In most cases, volumes, travel times and queues are used to
calibrate simulation models, rather than detailed driving characteristics such as speed and
acceleration patterns. However, these driving behavior parameters determine the vehicular
emissions to a great extent. A study was carried out in which the driving behavior parameters
in a microscopic simulation model (VISSIM) were calibrated using real trajectories collected
by image processing at an intersection in Rotterdam. The sensitivity of the simulation results
for driving behavior parameters was investigated. The most influential parameters were
identified and adjusted to ensure that the simulation results were consistent with the observed
traffic and could provide valid estimations of the total production of emissions (Henk Van
Zuylen, 2012).
3. Methodology
Several factors affect the traffic signal timing, fuel consumption and emissions at
intersections. These parameters are increasing and decreasing of vehicle speed, the input
vehicles volume, type of traffic signal phasing, type of lane, effective green time, cycle length
and etc.
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 146
Volume5 Issue2 2014
Traffic signal timing have optimized due to Iran standards after identifying the main factors
affecting traffic signal timing and considering the simulation software. Intersection’s
information related to traffic signal has been obtained from comprehensive traffic company.
finally a comparison have done between the software and the appropriate software in terms
of time, speed and accessibility that could reduce emission and fuel consumption well.5
intersections for case study are Golbarg-Dardasht, Kamali-Karegar, Mahalati-10farvardin,
Shariati-Dolat, Zibadasht-Dehkadeh. Research process are presented in the following graph.
Figure 1: Study methodology
4. Case study
5 intersections from Tehran city in 5 different areas consist of north, south, center, east, west
have selected for giving conclusions and case study. We just introduce some information of 2
intersections because the traffic information and emission parameters for 5 intersections are
enormous and cannot propose in this study. As noted, equivalent coefficients accordance with
urban road regulations is used to convert public transport and motorcycles volumes to
passenger vehicles.
4.1 Traffic information of Shariati-Dolat intersection (north Area)
This intersection is shown in Figure 1 .at this intersection Dolat Street is sideway and from
East to West has 3 lanes and also from north to south and south to north has 3 lanes.
Emamzadeh Street as two-lane Minor Street enters to intersection. Intersection angle is 90
degrees. And has an intelligent 2 phase signal traffic. It also has separate turn right and turn
left from East to west. Cycle length in AM peak and PM peak time are 80 and 69 seconds
respectively. Traffic volume in AM peak time in main road is 2202vehicles and 1993
vehicles in lateral direction and 2128 vehicles in main road and 1502 vehicles in PM peak
hours along the lateral direction in 2013.
5.2 Second simulation with Aimsun traffic simulator
The proposed output in table 1 and 2 were obtain after optimizing and putting the traffic
information into Aimsun simulator software by second simulation in compare with first
simulation. As observed in tables with decreasing in cycle length, delay and traveled time,
fuel consumption and emissions have been decreased and traffic flow, average speed
increase. It is noteworthy that the estimated fuel consumption or emissions should be carried
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 147
Volume5 Issue2 2014
out according to the amount of traffic flow. It can be seen that the overall amount of delay,
fuel consumption and emissions have been effectively reduced with little accuracy in results
of Secondary simulation and compare them with traffic flow.
Figure 2: Shariati-Dolat Intersection
4.3 Traffic information of Mahalati-10 farvardin intersection (south area)
This intersection indicates in fig 2.at this intersection Mahalti Street from East to West has 5
lanes and 10 farvardin streets from north to south and south to north has 4 lanes. Intersection
angle is not 90 degrees. And has an intelligent 3 phase signal traffic. It also has separate turn
in 4 directions. Cycle length in AM peak and PM peak time are 85 and 98 seconds
respectively. Traffic volume in AM peak time in main road is 2936 vehicles and 1516
vehicles in lateral direction and 3628 vehicles in main road and 1414 vehicles in PM peak
hours along the lateral direction in 2013.
Figure 3: Mahalati-10 farvardin Intersection
4.4. Simulation and optimization results
4.4.1First simulation with Aimsun traffic simulator
5 intersections studied geometrical plan is the first and most important step to enter data into
the Aimsun software. In this section the background of geometric design in AutoCAD format
or the images from Google earth or Google maps put into the Aimsun software as layout
before drawing the intersections plan.
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 148
Volume5 Issue2 2014
4.4.2 Optimization with synchro software
After the initial simulation and obtain outputs such as delay time, traveled distance, traffic
flow, vehicle average speed, travel time, fuel consumption and emissions like HC, CO, NOX
by Aimsun software. Signal timing optimization is done by Synchro software.Overall the rate
of cycle length about 27.05,10 % have been decreased at Mahalti-10 farvardin and Shariati-
Dolat intersections than previous case before optimization in AM peak time and also
41.83 ,31.88 % have been decreased in PM peak time respectively.
Figure 4: Geometric plan of Mahalti-10 farvardin Intersection
Figure 5: Geometric plan of Shariati-Dolat Intersection
Figure 6: Cycle length and Geometric plan of Mahalti-10 farvardin Intersection before
optimization in AM peak time by Synchro software
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 149
Volume5 Issue2 2014
Figure 7: Cycle length and Geometric plan of Shariati-Dolat Intersection before optimization
in AM peak time by Synchro software
Figure 8: Cycle length and Geometric plan of Mahalti-10 farvardin Intersection before
optimization in PM peak time by Synchro software
Figure 9: Cycle length and Geometric plan of Shariati-Dolat Intersection before optimization
in PM peak time by Synchro software
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 150
Volume5 Issue2 2014
Figure 10: Cycle length and Geometric plan of Mahalti-10 farvardin Intersection after
optimization in AM peak time by Synchro software
Figure 11: Cycle length and Geometric plan of Shariati-Dolat Intersection after optimization
in AM peak time by Synchro software
By examining changes in tables and considering traffic flow, it can be seen that the amount of
delay, fuel consumption, emissions such as HC, CO, NOX and travel time have been
decreased with improving cycle length and the rate of traffic flow, vehicles average speed
increased in both AM and PM peak hours at each intersection. Thus providing accurate traffic
signal timing optimization algorithms at intersections in Synchro software and observing
changes in Aimsun traffic simulator could provide significant reduction in fuel consumption
and emissions.After second simulation in Aimsun software the percent of flow /capacity in
AM peak time are represent as sample in figure 13 and 14.
Figure 12: Cycle length and Geometric plan of Mahalti-10 farvardin Intersection after
optimization in PM peak time by Synchro software
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 151
Volume5 Issue2 2014
Figure 13: Cycle length and Geometric plan of Shariati-Dolat Intersection after optimization
in PM peak time by Synchro software
Table 1: Output from second simulation, compared with the first simulation at Mahalati-10
farvardin intersection by Aimsun software
Current
case unit
AM
peak time
in first
simulation
AM Peak
time in
second
simulation
PM
peak time
in first
simulation
PM Peak
time in
second
simulation
Delay
time
s/k
m 57 55.7 68.6 61.6
Traffic
flow
Veh
/hr 4614 4677 5050 5980
Average
speed
Km
/hr 35.6 35.7 33.7 34.6
Travel
time
s/k
m 124 122.6 135.2 128.4
Traveled
distance km 1573 1562 1767.6 1741.8
Fuel
consumption liter 198 197.5 225.4 217.2
CO Kg 22.4 22.3 26.2 25.1
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 152
Volume5 Issue2 2014
HC Kg 1.75 1.2 2.1 1.9
NO Kg 0.36 0.30 0.42 0.39
Table 2: Output from second simulation, compared with the first simulation at Shariati-Dolat
intersection by Aimsun software .
Current
case
uni
t
AM
peak time in
first
simulation
AM Peak
time in
second
simulation
PM peak
time in first
simulation
PM Peak
time in
second
simulation
Delay
time
s/k
m 74.6 71.9 52.4 39.7
Traffic
flow
Ve
h/hr 4332 4406 3619 3643
Average
speed
Km
/hr 31 31 35.9 37.2
Travel
time
s/k
m 142.9 140.4 120.7 108.1
Traveled
distance km 1032.6 1050.9 850.1 847.2
Fuel
consumption
lite
r 200.90 200.24 133.9 130.6
CO Kg 20.2 19.1 13.7 12.8
HC Kg 1.5 1.38 1 0.91
NO Kg 0.39 0.19 0.25 0.13
Figure 14: The percent of flow/capacity in AM peak time at Mahalati-10 farvardin
intersection
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 153
Volume5 Issue2 2014
Figure 15: The percent of flow/capacity in AM peak time at Shariati-Dolat intersection
5. Conclusions
The review of previous studies in Iran and other countries indicated that extensive research
on traffic signal timing optimization to reduce delay time, total travel time and queue length
have done. However, few of these studies regarding the traffic signal timing optimization on
reducing fuel consumption and emissions. As was pointed out during the study, traffic signal
timing optimization and simulation can influence to reduce fuel consumption and emissions,
such HC, CO, NOX. So 5 intersections as case study have selected in this article. Traffic
information, geometric design and traffic signal timing enter to Aimsun software as the first
step for simulating. After simulation primary output such as delays, traffic flow, traveled time,
traveled distance, vehicles average speed ,fuel consumption and emissions have
acheived.Then optimization has done with synchro and to observe changes, second
simulation considered in this study. For sample percentage changes of Mahalati-10 farvardin
intersection are given in table 3.
Table 3: percentage changes of Mahalati-10 farvardin intersection
Current case unit
Percentage
changes in AM
peak time
percentage
changes in
PM peak time
Delay time s/km -2.28% -10.20%
Traffic flow Veh/
hr +1.36% +18.41%
Average
speed
Km/
hr +0.28% +2.67%
Travel time s/km -1.12% -5.02%
Traveled
distance km -0.69% -1.45%
Fuel
consumption liter -0.25% -3.63%
The impacts of traffic signal timings optimization on reducing vehicle emissions and fuel consumption by
Aimsun and Synchro software's (Case study: Tehran intersections)
Ali Mansour Khaki,Pegah jafari Haghighat Pour
International Journal of Civil and Structural Engineering 154
Volume5 Issue2 2014
CO Kg -0.44% -4.19%
HC Kg -31.42% -9.52%
NO Kg -16.66% -7.14%
Acknowledgement
This research was taken from Pegah Jafari Haghighatpour thesis and supported by
Department of Engineering, Islamic Azad University South Tehran Branch of Tehran, Iran.
The authors are grateful to Tehran Traffic Control Company and Dr Ali Mansourkhaki of
Civil Engineering department, University of Science and Technology for his help with this
thesis.
6. References
1. Energy and Economic magazine, International number: 1123-15632012, Tehran. Iran.
2. Adacher L., (2012), “A global optimization approach to solve the traffic signal
synchronization problem”, Procedia - Social and Behavioral Sciences, Published by
Elsevier Ltd. 54, pp 1270-1277.
3. Henk Van Zuylen, et al, (2012), Calibration of a microscopic simulation model for
emission calculation, Published by Elsevier Ltd, Transportation Research Part C, 31
pp 172–184.
4. Tehran traffic control company, October of 2013.
5. Aimsun 6.0.5 Simulation traffic software.
6. Synchro 8, Optimization and simulation traffic software.