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Unformatted text preview: simulated using the transporter module
of ARENA. The transporter module of ARENA allows the programmer to enter the speed
distribution for the vehicles. The inter-arrival times of the entities (vehicles) entering the
construction work zones were determined according to the field data collected. The
vehicle type assignment (i.e. car or truck) along with the lengths were made at the point
of entry. The vehicles were represented with the entity-transporter pairs in the system.
When the vehicles entered the system, the speed distribution functions were assigned to
the vehicles using transporters.
Another important issue in traffic simulation was the headway and the spacing
between the vehicles. Headway is defined as the time between successive vehicles as they
pass a point on a lane or roadway, using a common reference point on both vehicles and
spacing is defined as the distance between successive vehicles in a traffic stream, as
measured from front bumper to front bumper . In order to specify the headways and
spacing between the vehicles, initially, the headway and spacing were determined
according to the arrival time of the vehicles. The difference in vehicle arrival times 52
determined the headways and spacing. Additional length was added to the length of the
vehicles to maintain the minimum spacing during simulation.
The travel time (delay time) in the work zone was determined according to the
speed profiles of the vehicles in the work zone.
The model was evaluated using the data collected in the field. The use of real
world data allowed us to compare the outputs of the model and to analyze the accuracy of
About 1750 statements were used in the program to model traffic. Most of the
modules used at the stations for lane changing behavior were used with small changes in
the statements. One simulation run (replication) took about 30 minutes on a PC with 2.8
GHz processor and 1.0 GB RAM.
3.2.2 Design of the ARENA Traffic Simulation Model 22.214.171.124 Input Variables
The traffic data was entered into ARENA simulation program by using number of
variables which defined the system. According to these input variables the program
computed the output variables. The following variables were entered in order to get the
126.96.36.199.1 Construction Zone Configuration
The model was developed for two lane traffic configuration. Construction work
was performed on the passing lane of the road and the passing lane was closed for 5600
feet. The map of the construction zone is given in Figure 1. Vehicles were simulated 53
beginning from 700 feet in advance of the first “Left Lane Closed Ahead” sign. Then the
second and third lane closure signs were placed 1200 feet and 1700 feet after the
beginning of the simulation. After 500 feet from the third left lane closure sign, the lane
closure taper was begun. The length of the lane closure taper was 150 feet. One lane road
(after the left lane merge) shifted to the shoulder at 2300 feet with 300 feet taper. After
the merging of left lane and shifting of right lane to the shoulder, one lane road in
construction zone was simulated for 350 feet. After 3000 feet from the beginning of the
simulation start point, vehicles left the system. The dimensioning and the placement of
the traffic signs and drums are given in Figure 13. 3 2 1
1. First “Left
Ahead” Sign Figure 13: Work Zone Configuration used in the Example Simulation 54
The construction zone in ARENA simulation program was modeled by using the
intersections and links elements of the program . Intersections were defined at the
changes in the construction zone. And the links defined the distances between the
intersections. These two elements defined the network system in the simulation.
Originally the system was simulated for 14000 feet. It was starting 7950 feet
before the left lane closure taper and ending 6050 feet after the taper. The simulation run
length using the original distances took 3 – 5 hours for 1 replication. In order to decrease
the simulation runtime, the distances for the construction zone were reduced. The
reduction of the distances would not cause any loss of data, since the objective of the
model was to identify the queue length and the waiting time at the lane closure taper.
188.8.131.52.2 Inter-arrival Time Distribution (Entity Arrival)
Vehicle entry to the system was modeled using the create module of ARENA
simulation program. Actual inter-arrival times of the vehicles at the beginning of the
work zone were collected in the field. As mentioned earlier in section 184.108.40.206 [page 26]
the inter-arrival times of the vehicles were analyzed and a spreadsheet for determining
the cumulative percentages of inter-arrival times for given hourly traffic counts was
established. Using the spreadsheet, inter-arrival times of vehicles for 24- hour time period
for a weekday were determined using the actual count data from 08/20/2004 Friday.
Hourly vehicle counts...
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This document was uploaded on 02/26/2014 for the course E 515 at University of Louisiana at Lafayette.
- Spring '13