A Framework for Traffic Planning and Forecasting using Micro-Simulation Calibrations

IT in Industry, vol. 2, no. 1, 2014 Published online 8-Aug-2014
Copyright © Authors 25
A Framework for Traffic Planning and Forecasting
using Micro-Simulation Calibrations
David Tien
School of Computing and Mathematics
Charles Stuart University
Bathurst, Australia
Yung. C. Liang
Department of Electrical and Computer Engineering
National University of Singapore
Singapore
W. L. Loh
Department of Electrical and Computer Engineering
National University of Singapore
Singapore
Evgeni Nurminski
Institute of Automation and Control Processes
Russian Academy of Science
Russia Federation
Abstract—This paper presents the application of micro-
simulation for traffic planning and forecasting, and proposes a
new framework to model complex traffic conditions by
calibrating and adjusting traffic parameters of a micro-
simulation model. By using an open source micro-simulator
package, TRANSIMS, in this study, animated and numerical
results were produced and analysed. The framework of traffic
model calibration was evaluated for its usefulness and
practicality. Finally, we discuss future applications such as
providing end users with real time traffic information through
Intelligent Transport System (ITS) integration.
Keywords—traffic congestion; traffic planning; traffic
modeling; micro-simulations;TRANSIMS
I. INTRODUCTION
The rapid movement of people and goods is essential to
economic growth [1], and yet traffic congestion increases
travel times, traveler stress, and accident rates; reduces
mobility, accessibility, and system reliability; and results in
loss of productivity and environmental degradation [2]. This is
especially evident in Russia, the focus of this study.
In Russia, the road system in the vast country is mostly
underdeveloped. Many regions are still isolated from an
established road network and have no access to federal
highways. Despite being the capital of a country with vast
territorial resources, Moscow roads occupy only 8.7% of
urban space. The levels of motorization in major Russian
cities, range from around 250 to 400 cars per thousand
inhabitants. The levels are modest in comparison to the
world's megacities [3]. However, the severity of persistent
traffic jams in these Russian cities is way more serious. There
is a significant gross imbalance between road capacity and the
real level of motorization in Russia.
Russia loses close to 3% of its annual gross domestic
product (GDP) because of poor roads alone. Meanwhile, there
is also the issue of road safety. The casualty statistics for
Russia is high, fluctuating around 100 deaths per 100,000
vehicles as compared to Organization for Economic Co-
operation and Development (OECD) member countries, where
the figures are as low as 9-18 deaths per 100 thousand vehicles
[3].
Russia Federation's main concern is to pioneer road
development over their national territory, eventually ensuring
the country's global and local land communications. To
achieve their goals, the Russian authorities have renewed their
efforts in recent years to improve their traffic networks.
Russian Federation had unveiled their transportation plans and
policy in place for up to the year 2030 to combat the traffic
and to meet their goals of providing safe, efficient and reliable
transport. The initial motivation came about as part of the
country's preparation to host a number of major events such as
the 24th Asia Pacific Economic Cooperation (APEC) summit
in 2012, the Winter Olympic Games in 2013, and the
Paralympics Games in 2014. The APEC summit was held on
Russky Island, near the port of Vladivostok in the far east of
the country. To facilitate the movement to the island, a $1
billion-plus USD world longest cable stayed suspension bridge
was built to link Vladivostok and Russky Island over the Strait
of Bosporus. It was part of a $6 billion project which includes
other facilities such as a conference centre and luxury hotels.
Another major traffic improvement project is the construction
of the new toll link between the two largest Russian cities,
Moscow and St Petersburg [3].
Traffic experts are not optimistic in the outlook of the
government's development strategy, which essentially follows
the old Russian Empire’s cart-road structure with all major
roads converging to Moscow. This will result in a lack of
quality roads linking neighboring regions in the vast country.
Roads are still built based on mathematical models and
numerical calculations. Traffic flows are estimated based on
road geometry with reference to the Highway Capacity
Manual [4, 5]. Another traditional modelling approach is the
four step model [6]. The four steps are: trip generation, trip
distribution, modal split, and network assignment. Even
though the four step approach suffices in providing moderate

success in the aggregate [6], it cannot capture traffic details.
These traffic models are not able to account for traffic
condition changes as a result of dynamic factors in traffic
demand and supply. This paper introduces a model calibration
framework in adjusting model parameters to better reflect real
traffic conditions. The results are evaluated to determine their
potential use in future traffic predictions and forecasting.
Simulation refers to the movement of people and/or
vehicles on the network and is used to estimate the state of the
system (link travel times, turn penalties, link flows) when pure
mathematical and analytical models are inadequate to do so
[7]. Traffic systems can be modeled differently and there are a
wide variety of traffic models in which the traffic systems can
be classified under. There are four ways to classify traffic
models: physical interpretation, level of detail, discrete versus
continuous, and deterministic versus stochastic [8].
Depending on the level of detail of the traffic stream being
modelled, simulation models are generally classified as
macroscopic, microscopic, and mesoscopic models.
Macroscopic models simulate traffic flow using aggregate
stream characteristics such as speed, flow, and density, and
their relationships. Microscopic models simulate individual
vehicles, their characteristics and interactions on a second or
sub-second basis [9]. These models require large amount of
traffic data and analysis resources. The required data is
significantly more extensive and complex than other modeling
approaches. Mesoscopic models, on one hand simulate
individual vehicles, on the other hand describe their activities
and interactions based on aggregate relationships. In a recent
review paper, a number of traffic simulation softwares were
compared [10]. TRANSIMS stood out from the rest of the
simulator packages through its free use and documentation
alone. Together with the GUI simulation and visualization
capabilities, TRANSIMS was chosen for this study.
II. MICRO-SIMULATION USING TRANSIMS
This project aims to study the use of micro-simulation
models in modeling complex traffic situations including
inclement weather, congestion pricing, highway/freeway
changes, incidents, construction and work zone activities. A
main focus of this work is to determine what parameters can
be calibrated to better simulate dynamic traffic conditions. The
final simulation results is then evaluated to determine its
performance and the possibility of integrating into modern
Intelligent Transport Systems (ITS).
Fig. 1. Network view of Alexandria in QuantumGIS.
This study works on the network and census information
for Alexandria, Virginia. This is a sample dataset provided
with TRANSIMS simulator package. The data was distributed
by the U.S. Census Bureau for the Year 2000 Census. The
Public Use Micro data Sample (PUMS) provides complete
household records for a five percent sample of households
within Public Use Micro data Areas (PUMAs) that contain
approximately 100,000 people. The dataset provides tables of
various household attributes summarized at several levels of
geography. Block Groups are geographic subdivisions that
contain approximately 1,000 persons. The Alexandria_4.0.06
test case data uses a “real-world” network with 3,600 links and
roughly 420,000 trips. The Alexandria test case data illustrates
the typical use of TRANSIMS model implementation using
actual real-world data to represent the amount of travel
demand utilizing the region’s transportation system [11]. The
model study included all potential areas that might be
impacted by the proposed changes, Fig. 1. The morning (from
7 am to 10 am) and evening (from 5 pm to 8 pm) peak hour
periods have been selected as the temporal boundaries for the
analysis. Simulated traffic data at hourly averages and 15
minutes intervals will be collected.
TRANSIMS is a widely known agent-based model for
traffic simulation, combining demand modeling and flow
behavior. TRANSIMS requires large amounts of detailed data
and computing resources as it models the large scale dynamics
of a system. TRANSIMS is an open source micro simulation
package which includes an integrated set of tools as binaries
executables. In version 4.0.8, there is a total of 71 executables,
which will be referred to as programs or modules
interchangeably. The goal of the TRANSIMS micro-
simulation is to load traffic onto the network and iterate
towards the state of Nash Equilibrium where no travelers will
improve their travelling time by changing travelling routes.
Sub-modules include population synthesizer, activity
generator, route planner and micro simulator. An iterative
feedback process draws the output from the sub-modules and
fed in as input to the next stage. This process iterates and
converges to equilibrium. At equilibrium, travelers are
modeled with a transportation mode to travel on a path that is
best for the overall population [12].
III. BASE MODEL DEVELOPMENT
The base model was developed using TRANSIMS Studio
0.9.9, which provides an integrated development environment
(IDE) for TRANSIMS. The IDE supports the development of
Python 2.6 user scripts, driven by the TRANSIMS Run Time
Environment (RTE). The RTE is a Python module that
automates much of the complex interaction among the
TRANSIMS modules. TRANSIMS utilizes control files in
which parameters can be modified. There are five main python
scripts (ConvertNet.py, ConvertTrips.py, RouterRuns.py,
MicrosimulationRuns.py, and Visualize.py) facilitating the
interaction of program modules and control files.
A. Link-Node Diagram
The link-node diagram, that can be created directly in
TRANSIMS or through other computer-aided design (CAD)
softwares, identifies the streets and highways modelled in the

simulation. Each node represents the x-y coordinates of the
intersection of two or more links. The node coordinates can be
obtained from maps, aerial photographs, or other means. Links
represent the one-directional segments of streets or freeways,
with shape points to represent link curvatures. The link-node
diagram provides the framework of the model. In addition, the
following parameters are required: number of lanes, lane
width, link length, type, and curvature. The link-node diagram
is stored as TRANSIMS flat files (text-based). They can be
converted to shape files which are viewable by GIS tools such
as ArcGIS and QuantumGIS.
The formation of the diagram can be done through a series
of execution of TRANSIMS programs. Without the use of
TRANSMS Studio, this was achieved through writing a batch
shell script. The script file automates the entire simulation
process, handling all the input and output files locations in the
project folder and specification of the simulation programs
parameters. Alternatively, with TRANSIMS Studio running
the Alexandria dataset, the scripting could be done in Python
in the Integrated Developer Environment (IDE).This approach
is way more efficient than the manual batch scripting process.
The link node diagram is generated by running the modules
ArcNet and TransimsNet in the python script ConvertNet.py.
B. Traffic Control at Intersections and Junctions
TRANSIMS implements the following traffic controls at
intersections and junctions: no control, yield signs, stop signs,
and signals (pre-timed and actuated). Intersection details are
added to the network by the module IntControl in the
ConvertNet.py. Running this module will generate the
following signal files for future use in micro-simulation runs:
Signalized Node, Unsignalized Node, Timing Plan, Phasing
Plan, Detector, and Signal Coordinator Files.
C. Traffic Demand Data
As TRANSIMS is a demand based modeling simulator,
trips are generated based on travelers demand which can be
derived from the O-D table, and other demand data such as
vehicle characteristics data. There are two approaches to
generating travelers demand. One is trip based, where O-D trip
tables are used to synthesis the travelling population and their
travel plans. The alternative approach is tour-based, where
census survey data on the network is used for activity
generation. Since census data are not readily available, the trip
based approach was used to generate the traffic demand data.
The first step in this approach is to convert the O-D trip
table and trip times to other demand files such as travelling
population, vehicles and trip plans etc. These traffic demand
files are essential for the later stages in the simulation process.
They will be generated by executing the program module
ConvertTrips with the O-D trip table as the main input. The
script, ConvertTrips.py is responsible for the traffic demand
data generation.
D. Driver Behavior Data
Driver behavior data in TRANSIMS represents the driver's
aggressiveness (give-way, lane changing) and response to the
traffic conditions.
TABLE I. DEFAULT DRIVER BEHAVIOR DATA
Micro-Simulator Variables Values
Look Ahead Distance 260 meters
Look Ahead Lane Factor 4.0
Look Ahead Time Factor 1.0
Permission Probability 55.0 percent
Plan Following Distance 525
Driver Reaction Time 0.7, 0.8, 0.9, 1
Slow down Percentage 10, 20
Slow Down Probability 10, 15 , 20
Table 1 shows the default values of the driver behavior
parameters in the micro-simulator. It should be noted that
these values can be calibrated to match observed field data
provided that the field data is available. The driver behavior
values can be changed and calibrated to simulate more
complex situations.
E. Simulation Run Control Data
Before running simulations in TRANSIMS, setting up the
run control parameters in the control files are required. These
parameters include: simulation duration, outputs (e.g., reports,
animation files, or both), and resolutions of simulation results
(e.g., temporal and special resolution). In addition, control
keys and other parameters can be customised.
IV. MODELING CALIBRATION FOR COMPLEX SCENARIOS
By using TRANSIMS Studio, a base working model with
error-checking was developed. However, complex situations
due to external factors cannot be directly represented in the
base model. This limitation is mainly constrained by the
micro-simulator capabilities and available options. For
example, TRANSIMS does not have the parameters that
explicitly represents inclement weather conditions. To
overcome the limitation, we propose to use calibrations to
cover conditions that cannot be directly simulated by the
software. By calibrating the base model parameters, external
factors in various scenarios can be more realistically modeled
and simulated, and consequently, more accurate predictions
can be achieved [13]. A framework incorporating existing
calibration techniques to capture the influencing factors is
introduced. For each complex scenario, a certain set of
parameters need to be adjusted. Ideally observed field data to
reflect local conditions should be collected for calibration. In
this study, the set of adjustable parameters will be determined
without observed field data.
A. Calibration for Capacity
The capacity calibration step adjusts the global and link-
specific capacity-related parameters in the simulation model to
best replicate expected local field measurements for capacity.
This is an important step as capacity has a significant effect on
predicted system performance (delay and queues) [13]. In the
beginning, global calibration is performed to identify the

values for the capacity adjustment parameters that help best
reproduce the observed traffic capacities in the field [14].
HCM would be used as an alternative source of capacity target
values as actual field measurements are not attainable. Link-
specific capacity parameters are then adjusted to fine-tune the
model so that it matches the field-measured capacities at each
bottleneck more accurately. One approach in capacity
calibration is to perform search optimisation on model
estimates. As field measurements of capacity were not
available in this study, the HCM methodology will be used to
estimate capacity. The HCM methods should not be
considered a default technique since the estimates are not as
accurate as direct field measurements.
B. Obtaining Model Estimates of Capacity
In TRANSIMS, the outputs generated are vehicle volumes
for network links. The input traffic demand, that is, O-D trip
tables have to be manipulated to create a queue upstream of
the target section to be calibrated so that the model will report
the maximum possible flow rate through the bottleneck. If the
model does not initially show congestion at the same
bottleneck locations as exist in the field, then the traffic
demands coded in the model are temporarily increased to force
the creation of congestion at those bottlenecks. These
temporary increases must be removed after the capacity
calibration has been completed, but before the route choice
calibration step. If the model initially shows congested
bottlenecks at locations that do not exist in the field, it will be
necessary to temporarily increase the capacity at those false
bottlenecks (using temporary link-specific headway
adjustments). These temporary adjustments are then removed
during the fine tuning phase. The model runs should be
repeated several times and the maximum flow rate at each
location should be averaged across the runs. The minimum
required number of runs to obtain a value of capacity within a
desired confidence interval can be calculated.
C. Calibration Parameters Selection
Only the model parameters that directly affect capacity are
calibrated at this time. Each micro-simulation software
program has its own set of parameters that affect capacity,
depending on the specific car-following and lane-changing
logic implemented in the software. In TRANSIMS, the
parameters affecting capacity directly can be found in the
input link file. For each link connecting node A to B, the
parameters are as follows:
 Length: length in meters
 Lanes_AB: number of lanes from A to B
 Speed_AB: maximum speed allowed from A to B
 Lanes_BA: number of lanes from B to A
 Speed_BA: maximum speed allowed from B to A
The program module TransimsNet will automatically
provide an estimated value of the link capacity according to
the number of lanes and the length of the link. This estimated
capacity will be used in the Router module, but not the
Microsimulator module. Nevertheless, the capacity can be
modified in the link network files for calibration purposes. For
the base model, the default parameter values are assumed to be
the most optimal. For the complex situations, parameter values
are adjusted to HCM values and determined to be optimal.
D. Link-Specific Fine-Tuning
Once the optimal global capacity calibration parameter
values are identified and completed, there will still be some
locations where model performance deviates a great deal from
the field conditions. Therefore, the next phase is to fine-tune
the predicted capacity to match the location-specific
measurements of capacity as closely as possible. Link-specific
adjustments to cost or speed are made during this fine-tuning
phase. Link-specific capacity adjustments account for roadside
factors that affect capacity, but are not typically coded in the
micro-simulation network input data. Most simulation
software programs have link-specific capacity adjustment
factors that apply only to the subject link. In TRANSIMS,
these roadside links are known as 'pocket' subjected to the
facility type. Following are a few examples of facility types in
TRANSIMS: 1 = freeway; 2 = expressway; 12=bikeway;
14=light rail, and so on. Pocket lengths parameters are
specified in TRANSIMS net control files.
E. Route Choice Calibration
TRANSIMS micro-simulation model provide alternative
routing for travelers according to the route impedance values.
Routing is done through the router module in TRANSIMS
Studio. As complex situations would impact the route
chosen/taken by the travelers, the next step of the calibration
approach after capacity calibration is to perform calibration
with route choice parameters, Table 2. This is to a achieve a
better match to the expected traffic flows. In TRANSIMS, the
appropriate parameters should be chosen and the calibration
then proceeds through the same process as was used to
calibrate capacity.
TABLE II. ROUTE CHOICE PARAMETERS IN ROUTER CONTROL FILE
Router Parameters Values
Walk Speed 1.0 meters
Walk Time Value 20.0 impedance/sec
Vehicle Time Value 10.0 impedance/sec
First Wait Value 20.0 impedance/sec
Transfer Wait Value 20.0 impedance/sec
Distance Value 5.0 impedance/cent
Cost Value 1.0 impedance/meter
Transfer Penalty 1200 impedance
Maximum Walk Distance 2000 meters
Minimum Wait Time 60 seconds
Left Turn Penalty 300 impedance
Kiss Ride Stop Type Stop, Station, External
Max Kiss Ride Drop-off Walk Distance 100 meters
Parking Hours by Purpose 8.5, 2.5, 1.0, 1.0 hours

F. System Performance Calibration
Caution should be taken in making changes at this step as
it may affect the previous two calibration steps. Fine-tuning
adjustments made to the system performance parameters will
enable the model to better match the field measurements. As
of before, the HCM estimated values are applied. Calibrating
parameters for the module Microsimulator is important. These
parameters, defining the driver behavior, are the key attributes
in the complex traffic simulation scenarios. In addition,
vehicle characteristics such as acceleration and deceleration
are also affected by the local traffic situation. By adjusting
these key values, the traveler reaction to various complex
situations can be modeled. The default key parameters are
listed in Table 3.
G. Weather Conditions
Weather conditions have huge impacts on the efficiency of
transportation systems. Inclement weather reduces visibility
and traction of the road and affects driver behavior
significantly. Not only does experiencing weather conditions
affect driver behavior, but knowledge or warning of inclement
weather also has been seen to result in more cautious driver
behavior [15]. Drivers would normally reduce speeds and
increase headways leading to slowed traffic flow.
Additionally, driving under inclement weather shows a higher
frequency of acceleration and deceleration. The magnitude of
vehicles acceleration and deceleration significantly lower than
under dry weather. In short, inclement weather conditions
would impacts roadway surface conditions and driver
behavior, which result in increased delays and crash risks [16].
In this study, the types of inclement weather condition to
be analyzed will be light, heavy rainfall and light, heavy snow.
According to Highway Capacity Manual [5], the impact of
light rain on freeway capacity is minimal with percentage as
low as 0% reduction. For heavy rain, capacity reduction is
about 15%. For the case of snow and light snow, capacity
reduction ranges from 5% and 10% reduction. Heavy snow
would reduce capacity by a range between 25% and 30%.
TABLE III. KEY SIMULATION PARAMETERS FOR CALIBRATION
Micro-Simulator Parameters Values
Look Ahead Distance 260 meters
Look Ahead Lane Factor 4.0
Look Ahead Time Factor 1.0
Permission Probability 55.0 percent
Plan Following Distance 525
Driver Reaction Time 0.7, 0.8, 0.9, 1
Slow down Percentage 10, 20
Slow Down Probability 10, 15 , 20
Maximum Speed 37.5 meters/second
Maximum Acceleration 7.5 meters/second2
Maximum Deceleration 7.5 meters/second2
TABLE IV. HCM PERCENTAGE REDUCTION FOR INCLEMENT WEATHER
Variable
Range
(in/hr)
Categories
from HCM
2000
Capacities
(Percentage
Reduction)
Avg. Operating
Speeds
(Percentage
reduction)
Rain
0-0.01 Light 0 2-14
0.01-0.25 Light 0 2-14
>0.25 Heavy 14-15 5 - 17
Snow
<= 0.05 Light 5-10 8 -10
0.06-0.1 Light 5-10 8 -10
0.11-0.5 Light 5-10 8 - 10
>0.5 Heavy 25-30 30 - 40
In order to achieve the HCM recommended reductions,
parameters listed in Table 1 need to be adjusted. Most of the
parameters can be found in the control file for the module
Microsimulator. Refer to Table 7 in Section V for the full list
of calibrated values. The last three parameters are vehicle
performance values which can be modified in the vehicle input
file.
H. Congestion Pricing
Toll collections, often occur on freeways, are a unique
form of traffic control device. Toll collections usually result in
delays. With the mix of electronic toll collections (ETC) and
cash payments, vehicles can result in uneven queues that block
lanes, and significant weaving, ultimately resulting in safety
problems [17]. TRANSIMS has a data file type 'Toll' to model
toll payments for travelers utilizing links. Route choice as a
result of toll was explicitly represented as an additional cost
associated with the particular route path.
As road tolls will affect the travelers choice of route, route
choice calibration has to be done. In this case, the router
control file is analyzed for the required changes. Through
review of TRANSIMS documentation, it was determined that
the toll table can be included in the router control file for
modeling toll links in the network. Inclusion of the toll table in
the Router module was implemented to simulate tolls on the
target link. Within the router control file, the perceived
impedance value by the traveler is represented by the
parameter COST_VALUE. This parameter can be adjusted to
show the elasticity of travel demand related to costs.
TABLE V. TOLL PARAMETERS IN NETWORK FILES
Parameters Descriptions
Link Link ID on which the toll is collected
Dir
Node ID or direction code toward which the toll collection
is headed.
Start Start time for the toll collection
End End time for the toll collection
Use Vehicles type that must pay toll
Toll Cost of toll in cents

TABLE VI. PARAMETERS ADJUSTED FOR CONSTRUCTION AND WORK
ZONE ACTIVITIES, AND INCIDENTS
Downward Adjustments Upward Adjustments
Link capacity Driver reaction time
Link free flow speed Slow down percentage
Link speed limit Slow down probability
Plan following
Look ahead distance
Look ahead lane
Look ahead time
In some other simulation systems, toll collection can be
modeled with direct acceleration effects as vehicles slow or
stop to the necessary speed. Tolls are also effective in limiting
flow of vehicles and relieving crowded streets [18].
I. Construction and Work Zone Activities, and Incidents
The impacts of construction and work zone activities, and
incidents are reduction in capacity and the likely congestion as
a consequence. To capture the scenario in the simulation, the
parameters to adjust include driver behaviors, vehicle
performance values and link capacities. The modeling of
incidents was deemed similar to situations in construction and
work zone activities. In the scenario that a stalled vehicle stops
in the middle of the lane, the capacity of the road network link
is reduced. Similarly, in a scenario where a lane is heavily
used for parking, loading and unloading activities, the affected
parameters in TRANSIMS would be capacity parameters.
Hence, the related parameters were adjusted to model the
scenarios. As an extreme example, a solution would be to
remove the lane from the link as that yields the same result for
a lane blocked virtually all of the time. In this study, the link
with the afflicted lane will have the free flow speed, speed
limit and capacity adjusted accordingly. Table 14 summarizes
the possible changes to the simulation parameters in modeling
these situations.
Fig. 2. Static view of traffic intersection with labeled traffic nodes.
Fig. 3. Static view of traffic intersection with labeled traffic nodes.
Fig. 4. Animation view in TRANSIMS Visualiser.
V. RESULTS AND DISCUSSION
The visualization results of an intersection with high traffic
volume are given in this section. The corresponding links and
nodes of the intersection are shown in Fig. 2 and Fig. 3,
respectively. Animation output provides a quick view and
qualitative assessment of the overall performance of the traffic
simulation. The layers of data generated from the micro-
simulations are stored as TRANSIMS flat files. The snapshot
files can be converted to shape files (GIS data), using the
ArcUilities type tools (ArcNet, ArcPlan, etc), and visualized as
static images. By stringing up the individual images as frames,
a movie can be generated. TRANSIMS Studio and
TRANSIMS Visualizer can be used together to create and
view the simulation as an animation, Fig. 4.
Numerical results of TRANSIMS are stored in text output
files called “reports”, which contain information on simulated
traffic activities, summarized over time and/or space.
Statistical results can be extracted and analyzed through the
outputs of the micro-simulations, the link delay files. From
these files, performance reports with various statistics and
details can be generated. These include statistics such as
summarized network performance values, link volumes and
trip times. The module LinkSum in TRANSIMS helps to
generate the summarized reports from the link delay files. The
LinkSum reports include: (1) Top 100 Volume Capacity

Fig. 5. Time delay under various conditions.
Ratios, (2) Top 100 Link Volume, and (3) Network
Performance Summary.
There are various traffic performance measures that can be
utilized to measure the degree of traffic congestion in the
target road intersection. The traffic delays are tabulated and
plotted to show the impact of each complex situation on the
traffic efficiency, during the morning peak period from 7:00
AM to 10:00 AM. The results collected from the network
performance summary, generated from the LinkSum print
report, are shown in Fig. 5. The peak delay occurs at around
8:00 AM to 8:45 AM. This matches the animation output
where the target intersection is visibly much more congested.
The convergence at the end of the peak period suggests that
complex traffic situations have a much lesser impact when the
congestion level is already low. This marginal effect due to
varying degree of congestion is critical to transportation
professionals in traffic forecasting studies. In our study, heavy
rainfall and snow conditions were modeled, and they were
found to have the most impact on travel times. All the
parameters were adjusted with reference to previous traffic
studies such as the HCM and other best educated
approximations. Table 7 below shows the parameters adjusted
for raining and snowing.
Calibrating traffic parameters allows us to model complex
situations which was not possible with traditional macro-level
analysis. Traffic modeling with micro-simulation requires a
well-developed micro-simulator package and detailed network
data files. Census data such as population, travel activities and
trip tables are also required to simulate an accurate travelling
population. An accurate database for simulation purpose
requires huge data collection over long periods of time by
traffic engineers. In this study, availability of traffic data has
been the main limitation, affecting the accuracy and
practicality of the results. To compensate we used the best
estimates available in the field.
In our study using TRANSIMS, the effects of complex
situations are captured by proxy mechanisms that allow the
user to modify certain parameters in order to achieve similar
resulting effects. The proposed calibration framework is
limited as a form of proxy mechanism. Also, the calibration
TABLE VII. KEY PARAMETER SETTINGS
Parameter Base Value Raining Snowing
Look Ahead
Distance
260 meters 500 meters 500 meters
Look Ahead
Lane Factor
4.0 8.0 8.0
Look Ahead
Time Factor
1.0 0.5 0.5
Permission
Probability
55.0 percent 55.0 percent 55.0 percent
Plan Following
Distance
525 650 650
Driver Reaction
Time
0.7, 0.8, 0.9, 1 1.4, 1.6, 1.8, 2 1.4, 1.6, 1.8, 2
Slow down
Percentage
10, 20 20, 30 25, 35
Slow Down
Probability
10, 15, 20 20, 25, 30 20, 25, 30
Maximum Speed 37.5 m/s 37.5 m/s 37.5 m/s
Maximum
Acceleration
7.5 m/s2
6 m/s2
3.8 m/s2
Maximum
Deceleration
7.5 m/s2
6 m/s2
3.8 m/s2
approach does not capture the effects on lane-changing and
acceleration in congested conditions, where maximum and
desired speeds are of marginal importance. Even for these
mechanisms that exist in other traffic simulation models, there
are very few empirical results in the literature to guide the user
in setting up and changing the values of the relevant
parameters to quantify the effect of various factors [19].
Moreover, in real world, there is often a combination of
complex traffic situations such as inclement weather coupled
with traffic incidents. For these different situations to be
captured and modeled accurately, the observed field values for
calibration must be determined to be correct for the right
combination of complex factors. In our proposed framework,
complex situations are modeled individually and
independently. Other than micro-simulations to capture
complex external factors, it is also important to model the
travel demand in the overall area at macroscopic scale.
Regression models for each complex situations can be
developed to validate the model used. For example, a linear
regression model could be proposed to quantify and predict
the combined weather impact on average freeway operating
speed [20].
VI. CONCLUSION
One aspect of future work is to include finer details of
information and traveller responses in the model. Existing
route choice models are primarily travel time based [19]. This
is significant as a better model in route choice behaviour of
travellers will provide better simulation results. In the case of
TRANSIMS, the route choice is based on perceived
impedance. In particular, a planning tool could be used in
tandem with simulation packages to achieve better accuracy
and practicality. Popular planning tools include TransCAD
and TransModeler.
Additionally, other than traffic planning, the concept of
using micro-simulation results to improve traffic controls

using Intelligent Transport Systems (ITS) can be explored.
ITS plays a critical role in many of the current world research
in traffic engineering [21]. Many of the traffic studies
performed today seek to integrate their results with ITS
systems in their local cities. This project can be extended to
explore how micro-simulations can be best integrated with an
ITS system. The main idea is to build traffic sensors at various
traffic intersections and major links. These traffic sensors will
collect real time data and sent them over to the back end
servers for processing. The servers at the back end could
perform fast micro-simulations and relay the results back to
the travellers. The travellers would be able to receive critical
traffic information such as expected travel time/delay through
their smart phones.
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