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    Development of VISSIM Base Model for Northern

    Virginia (NOVA) Freeway System

    By:

    Srividya Santhanam

    Byungkyu (Brian) Park

    Research Report No. UVACTS-13-0-124

    June 2008

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    A Research Project Report

    For the Northern Region Operations

    Virginia Department of Transportation (VDOT)

    Srividya Santhanam

    Department of Civil Engineering`

    Email: [email protected]

    Dr. Byungkyu (Brian) Park

    Department of Civil Engineering

    Email: [email protected]

    Center for Transportation Studiesat the University of Virginia produces outstanding transportationprofessionals, innovative research results and provides important public service. The Center for

    Transportation Studies is committed to academic excellence, multi-disciplinary research and to developing

    state-of-the-art facilities. Through a partnership with the Virginia Department of Transportations (VDOT)Research Council (VTRC), CTS faculty hold joint appointments, VTRC research scientists teach

    specialized courses, and graduate student work is supported through a Graduate Research Assistantship

    Program. CTS receives substantial financial support from two federal University Transportation Center

    Grants: the Mid-Atlantic Universities Transportation Center (MAUTC), and through the National ITS

    Implementation ResearchCenter (ITS Center). Other related research activities of the faculty includefunding through FHWA, NSF, US Department of Transportation, VDOT, other governmental agencies and

    private companies.

    Disclaimer:The contents of this report reflect the views of the authors, who are responsible for the factsand the accuracy of the information presented herein. This document is disseminated under the

    sponsorship of the Department of Transportation, University Transportation Centers Program, intheinterest of information exchange. The U.S. Government assumes no liability for the contents or use

    thereof.

    CTS Website Center for Transportation Studieshttp://cts.virginia.edu University of Virginia

    351 McCormick Road, P.O. Box 400742

    Charlottesville, VA 22904-4742434.924.6362

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    iii

    1. Report No. UVACTS-13-0-124 2. Government Accession No. 3. Recipients Catalog No.

    4. Title and Subtitle 5. Report Date

    Development of VISSIM Model for Northern Virginia (NOVA) Freeway System June 2008

    6. Performing Organization Code

    7. Author(s) 8. Performing Organization Report No.

    Srividya Santhanam and Byungkyu (Brian) Park UVACTS-13-0-124

    9. Performing Organization and Address 10. Work Unit No. (TRAIS)

    Center for Transportation Studies

    University of Virginia 11. Contract or Grant No.

    PO Box 400742

    Charlottesville, VA 22904-7472

    12. Sponsoring Agencies' Name and Address 13. Type of Report and Period Covered

    Northern Region Operations

    Virginia Department of Transportation

    Final Report

    14. Sponsoring Agency Code

    15. Supplementary Notes

    16. Abstract

    This project aims at providing the Northern Region Operations (NRO) staff with a microscopic traffic simulation model for

    major Northern Virginia (NOVA) Freeway system using VISSIM. The network includes 4 Interstate Highways (I-66, I-95, I-395, and

    I-495) and a State Highway 267. This report provides details on the tasks of network building, O-D estimation and model calibration.

    The O-D matrices were estimated on the basis of traffic counts obtained from video cameras, sensors, and average annual daily traffic

    using QUEENSOD method. Latin Hypercube experimental design approach was used for the calibration. The project deliverables to

    the Northern Region Operations include calibrated network for the NOVA freeway system in VISSIM program along with O-D tables

    and base measures of effectiveness.

    17 Key Words 18. Distribution Statement

    Microscopic traffic simulation model, O-D Estimation, Calibration, LatinHypercube experimental design, Measures of Effectiveness (MOE)

    No restrictions. This document is available to thepublic.

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    iv

    Abstract

    This project aims at providing the Northern Region Operations (NRO) staff with a

    microscopic traffic simulation model for major Northern Virginia (NOVA) Freeway

    system using VISSIM. The network includes 4 Interstate Highways (I-66, I-95, I-395,

    and I-495) and a State Highway 267. This report provides details on the tasks of network

    building, O-D estimation and model calibration. The O-D matrices were estimated on the

    basis of traffic counts obtained from video cameras, sensors, and average annual daily

    traffic using QUEENSOD method. Latin Hypercube experimental design approach was

    used for the calibration. The project deliverables to the Northern Region Operations

    include calibrated network for the NOVA freeway system in VISSIM program along with

    O-D tables and base measures of effectiveness.

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    Table of Contents

    Abstract.............................................................................................................................. ivTable of Contents................................................................................................................ v

    List of Figures .................................................................................................................... vi

    List of Tables .................................................................................................................... vii

    Introduction......................................................................................................................... 1

    Purpose and Scope.......................................................................................................... 2

    Organization of the Report.............................................................................................. 2

    Chapter 1: Network Coding................................................................................................ 3

    1.1 Parking Lots and Nodes............................................................................................ 31.2 Vehicle Types and Traffic Composition................................................................... 41.3 HOV Lanes and Link/Connector Costs .................................................................... 5

    1.4 Toll Roads and Stop Signs........................................................................................ 8

    1.5 Driving Behavior Parameters Based on Link Type .................................................. 9

    Chapter 2: O-D Estimation ............................................................................................... 11

    2.1 Data Collection ....................................................................................................... 11

    2.1.1 Data from Detectors......................................................................................... 11

    2.1.3 Extrapolation of Missing Data ......................................................................... 21

    2.2 O-D Estimation Using QUEENSOD...................................................................... 242.3 Measures of Effectiveness Data Collection......................................................... 27

    Chapter 3: Simulation Model Calibration......................................................................... 28

    3.1 Introduction............................................................................................................. 283.2 Latin Hypercube Sampling ..................................................................................... 29

    3.3 Experimental Design Results.................................................................................. 30

    3.3.1 Simulation Model Setup .................................................................................. 313.3.2 Initial Evaluation.............................................................................................. 31

    3.3.3 Initial Calibration Latin Hypercube Design (LHD) for Driving Behavior... 363.3.3.1 Experimental Design Latin Hypercube Sampling ................................. 38

    3.3.3.2 Multiple Runs............................................................................................ 38

    3.3.3.3 Parameter Set Selection ............................................................................ 38

    Chapter 5: Measures of Effectiveness from the Calibrated Model................................... 47

    5.1 Counts and Speeds.................................................................................................. 47

    5.2 Travel Time and Delays.......................................................................................... 485.3 Density .................................................................................................................... 49

    Conclusions and Recommendations ................................................................................. 51References......................................................................................................................... 52

    Appendix A....................................................................................................................... 53

    Appendix B ....................................................................................................................... 81

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    List of Figures

    Figure 2.Northern Virginia (NOVA) Freeway network (source: Google map) ................. 1

    Figure 3. I-66 EB Mainline Flow Profiles ........................................................................ 21

    Figure 4. I-66 EB On Ramp Flow Profiles ....................................................................... 22

    Figure 5. I-66 EB Off Ramp Flow Profiles....................................................................... 22Figure 6. Flow Chart for Calibration Using Latin Hypercube Experimental Design....... 28

    Figure 7.Two-dimensional representation of a LHS of size 5 for X1 and X2 ................... 30

    Figure 8. I-66EB Network ................................................................................................ 31

    Figure 9. Simulated TT Vs Observed TT (6:00-6:30 AM)-Default Parameters............... 32Figure 10. Simulated TT Vs Observed TT (6:30-7:00 AM)-Default Parameters............. 33

    Figure 11. Simulated TT Vs Observed TT (7:30-8:00 AM)-Default Parameters............. 33

    Figure 12. Simulated Counts Vs Detector Counts for Station 2-Default Parameters....... 34

    Figure 13. Simulated Speed Vs Detector Speed for Station 2-Default Parameters.......... 34

    Figure 14. Simulated Counts Vs Detector Counts for Station 10-Default Parameters..... 35Figure 15. Simulated Speed Vs Detector Speed for Station 10-Default Parameters........ 35

    Figure 16.Simulated TT Vs Sample Case......................................................................... 39

    Figure 17. Simulated TT Vs CC1 ..................................................................................... 40

    Figure 18. Simulated TT Vs Observed TT (6:00-6:30 AM)-C98 (LHD_1)..................... 41

    Figure 19. Simulated TT Vs Observed TT (6:30-7:00 AM)-C98 (LHD_1)..................... 42

    Figure 20. Simulated TT Vs Observed TT (7:30-8:00 AM)-C98 (LHD_1)..................... 42Figure 21. Simulated Counts Vs Detector Counts for Station 2 C98 (LHD_1) ............ 43

    Figure 22. Simulated Speed Vs Detector Speed for Station 2 C98 (LHD_1)................ 43Figure 23. Simulated Counts Vs Detector Counts for Station 10 C98 (LHD_1) .......... 44Figure 24. Simulated Speed Vs Detector Speed for Station 10 C98 (LHD_1).............. 44

    Figure 1.A print screen of Step 1 in usage of Lane Closure.exe ...................................... 81

    Figure 2.A print screen of Steps 4-7 in Usage of Lane Closure.exe................................. 83

    Figure 3.A print screen of Functioning of Lane Closure.exe ........................................... 84

    Figure 4.A print screen of RSZ Data Reduction.exe ........................................................ 85

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    List of Tables

    Table 1.Cost Coefficients for each Traffic Composition.................................................... 7Table 2.Connector Costs..................................................................................................... 7

    Table 3. HOV Schedule for Corridors in NOVA Network ................................................ 8

    Table 4.Speed and Deceleration values used for lanes on SH 267..................................... 9Table 5.Detector Data Quality Summery by Interstate..................................................... 12

    Table 6. I-66 EB Volume Data from Detectors ................................................................ 16Table 7. I-66 EB Volume Data from Videos .................................................................... 16

    Table 8. I-66 WB Volume Data from Detectors............................................................... 17

    Table 9. I-66 WB Volume Data from Videos................................................................... 17

    Table 10. I-95 NB Volume Data from Detectors.............................................................. 18

    Table 11. I-95 NB Volume Data from Videos.................................................................. 18

    Table 12. I-395 NB Volume Data from Detectors............................................................ 19

    Table 13. I-395 NB Volume Data from Videos................................................................ 19

    Table 14. I-95 SB Volume Data from Detectors .............................................................. 20Table 15. I-395 SB Volume Data from Detectors ............................................................ 20

    Table 16. Extrapolation of Missing Data.......................................................................... 23

    Table 17. Details of OD Matrices for each Freeway ........................................................ 25

    Table 18. Relative Error for Simulations using Default Parameters ................................ 36

    Table 19.Relative Error for Simulations using C98 and Default Parameters................... 40Table 20. C98 and Default Parameters ............................................................................. 45

    Table 21. Stations defined for Simulated Counts and Speeds .......................................... 48

    Table 22. Travel Time Sections Defined in the Network ................................................. 49Table 23. Link IDs/Locations for Density ........................................................................ 50

    Table 1.Simulated Counts for I-66 EB ............................................................................. 53

    Table 2.Simulated Speeds for I-66 EB ............................................................................. 54

    Table 3.Simulated Travel Times for I-66 EB ................................................................... 55

    Table 4.Simulated Densities for I-66 EB.......................................................................... 57

    Table 5.Simulated Delays for I-66 EB.............................................................................. 58

    Table 6.Simulated Counts for I-66 WB............................................................................ 59

    Table 7.Simulated Speeds for I-66 WB............................................................................ 61Table 8.Simulated Travel times for I-66 WB ................................................................... 62

    Table 9.Simulated Densities for I-66 WB......................................................................... 63

    Table 10.Simulated Delays for I-66 WB .......................................................................... 65

    Table 11.Simulated Counts for I-95 and I-395 NB........................................................... 66Table 12.Simulated Speeds for I-95 and I-395 NB........................................................... 67

    Table 13.Simulated Travel Times for I-95 and I-395 NB ................................................ 68

    Table 14.Simulated Densities for I-95 and I-395 NB....................................................... 70

    Table 15.Simulated Delays for I-95 and I-395 NB........................................................... 71

    Table 16.Simulated Counts for I-95 and I-395 SB ........................................................... 73Table 17.Simulated Speeds for I-95 and I-395 SB........................................................... 74

    Table 18.Simulated Travel times for I-95 and I-395 SB .................................................. 75

    Table 19.Simulated Densities for I-95 and I-395 SB........................................................ 77

    Table 20.Simulated Delays for I-95 and I-395 SB ........................................................... 79

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    Final Report

    Development of VISSIM Base Model for Northern Virginia (NOVA)Freeway System

    June 2008

    Dr. Byungkyu Brian Park and Srividya Santhanam

    Traffic Operations Laboratory

    Center for Transportation Studies

    University of Virginia

    IntroductionThe purpose of this project is to provide Northern Region Operations (NRO) staff

    with a microscopic traffic simulation model for major Northern Virginia (NOVA)

    Freeway network using VISSIM. These freeways include four Interstate Highways (I-66,

    I-495, I-395, and I-95) and a State Highway (SH 267). This network shown in Figure 1 is

    referred to NOVA network in the remainder of the report.

    Figure 1.Northern Virginia (NOVA) Freeway network (source: Google map)

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    Purpose and Scope

    The project deliverables to the Northern Region Operations (NRO) staff are

    calibrated network for the NOVA freeway system in VISSIM program along with O-D

    tables and base measures of effectiveness. The main tasks involved in completing the

    project were: (1) network building, (2) OD estimation and (3) simulation model

    calibration.

    Organization of the Report

    The following chapters of this report describe the details on the important aspects

    of each task. The first chapter explains the network coding efforts in VISSIM and some

    important characteristics of the NOVA network. The second chapter presents the data

    collection and the O-D estimation efforts that were carried out for the project. The third

    chapter focuses on the procedure adopted for the calibration of the VISSIM freeway

    network model. The base measures of effectiveness for each of the corridors of the

    NOVA network have been tabulated in the Appendix A. Furthermore some guidelines for

    the usage of applications developed for the model have also been presented in the

    Appendix B.

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    Chapter 1: Network Coding

    Building an accurate VISSIM model from scratch requires scaled maps showing

    the real network in detail. In order to replicate the modeled infrastructure network to

    scale, aerial photos (which served as base maps) were obtained and used as background

    images and VISSIM network was traced exactly according to the scaled maps.

    Dynamic Assignment (DA) module was chosen to model the route choice

    behavior of drivers for the freeways. As such, the specification of Origin Destination

    matrices are needed for input flows. To define travel demand using an OD matrix, the

    area to be simulated is divided into sub-areas called zones and to model the points

    where vehicles actually enter or leave the road network, a network element called

    parking lot is created. To reduce the complexity of the network, parts of the network

    where paths could diverge are defined using network element node.

    The following sections list a few important aspects of the network.

    1.1 Parking Lots and Nodes

    a) There are two types of Parking Lots that can be used in DA module of VISSIM

    Abstract Parking Lot and Zone Connector. Abstract parking lots are used if the

    road network is detailed enough to represent actual parking lot. The vehicles

    approaching abstract parking lot slow down until they come to a stop at the

    middle of the parking lot. Their capacity is limited to 700 vehicles per hour per

    lane. When Zone Connectors are used, entering vehicles do not slow down and

    are just removed from the network as they reach the middle of the parking lot.

    Thus the entry capacity of a zone connector is not restricted and this type is

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    appropriate to model origin and destination points where traffic enters or exits the

    network without using real parking. Hence Zone Connectors were used to model

    the entry and exit points for the NOVA network.

    b) As mentioned earlier, nodes are created where paths diverge or merge. It is

    imperative to include the connectors at diverging and merging paths of the

    network within a single node.

    c) From the information given by the users definition of nodes, VISSIM builds an

    abstract network graph consisting of edges (which distinguish them from the

    links of the basic VISSIM network) when the Dynamic Assignment is started.

    The edges are the basic building blocks of the routing search. For all the edges

    travel times and costs are computed from the simulation and they are used in the

    route choice model.

    1.2 Vehicle Types and Traffic Composition

    In VISSIM, vehicles that share common vehicle performance attributes are added

    into a single group, categorizing vehicle population into vehicle types. Each vehicle type

    is defined with several attributes such as vehicle model, minimum and maximum

    acceleration/deceleration, weight, length, etc. Based on the characteristics of each

    corridor of the NOVA network, 3 main vehicle types were created GP, HOV and HGV.

    The GP type represented vehicles with a single occupant and those that used the General

    Purpose lanes on the Interstate Highways I-66, I-95 and I-395 of the NOVA network. The

    HOV type represented vehicles with 2 or more occupants on I-66; vehicles with 3 or

    more occupants on I-95 and I-395; thus making them eligible to use the HOV lane on the

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    corresponding corridors of the NOVA network (the HOV lanes are being operated during

    the peak hours). The HOV lane schedule for each corridor is listed in

    Table 3. The specifications and characteristics for these two types were identical

    to those of the default CAR type in VISSIM. The HGV type represented the heavy

    vehicles on the network with vehicle type characteristics of default HGV type in

    VISSIM.

    In VISSIM, the vehicle mix of each network entrance flow for the network is

    defined by traffic composition. For example, three traffic compositions were defined for

    the I-66 EB network: GP for general purpose lane use (100 % GP type), HOV for those

    eligible to use HOV lane (100% HOV type) and HV for general purpose lane use (100 %

    HGV type).

    1.3 HOV Lanes and Link/Connector Costs

    Some interchanges on I-66 of the NOVA network contain auxiliary lanes and it

    was observed during test simulations that vehicles chose the auxiliary lanes instead of the

    mainline path causing congestion in the nearby areas and eventually reducing the

    vehicular speeds. This undesired behavior during simulation was rectified by adding costs

    to the links containing the auxiliary lanes. Travel time, travel distance, and financial cost

    (e.g., tolls) are the factors that influence route choice in VISSIM. The General Cost for

    all edges is computed as a weighted sum:

    General Cost = * travel time + * travel distance + * financial cost (1)

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    The coefficients , , can be defined by the user for a particular vehicle class.

    Thus by adding financial cost on appropriate links, the route choice of the vehicles can be

    altered as desired during the simulation.

    As noted, the Outside Beltway section of I-66 features a High Occupancy Vehicle

    (HOV) lane (not barrier separated, open to HOV 2+ vehicles during the peak hours) and

    Hard Shoulders (open to all vehicles during peak hours). Simulation of this feature

    requires lane closure/open by time of day (simulation time) which VISSIM does not

    currently provide directly. Taking advantage of the VISSIM COM Interface Module, a

    separate application was developed in Visual C++ to implement this Lane Closure

    Facility. HOV only restrictions were enforced by creating separate vehicle type for the

    HOV eligible vehicles, and by closing the HOV only lanes to all non-HOV types.

    Just closing relevant lanes alone did not necessarily encourage HOV eligible

    vehicles to use the HOV lane. The DA in VISSIM needs to identify the HOV and

    General Purpose (GP) lanes as two separate routes in order to assign a realistic proportion

    of HOV eligible vehicles on the HOV lane/route. Since I-66 EB network is characterized

    by HOV lanes that are not barrier separated from GP lanes, the only way to make

    VISSIM identify it as separate path/route was by defining separate connectors and adding

    appropriate costs for these connectors. Hence separate connectors were defined between

    the upstream and downstream links consisting of the HOV lane while separate connectors

    were defined for the same links consisting of the GP lanes.

    A separate link cost coefficient was assigned to each vehicle type. Thus, based on the

    general cost computed using the cost coefficients and the link/connector costs assigned in

    the network, vehicle route choice became available in VISSIM. During the verification

    process undesired lane change behavior by HOV eligible vehicles was often observed. As

    vehicles moved from upstream link to downstream links, it was observed that the HOV

    eligible vehicles used the GP lane connector rather than using the HOV lane connector,

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    causing congestion at several nodes. To correct for this undesired vehicle movement,

    costs were introduced to GP lane connectors. Assigning cost coefficient to HOV

    vehicle type alone (assigning 0= to all other vehicle types) made the GP connector

    costs applicable to only HOV vehicles. Thus, magnitudes of the cost coefficients and

    connector costs were chosen in a manner that made the path with the HOV lane as the

    minimum-cost route available to HOV-type vehicles. The magnitudes of the costs and the

    coefficient values assigned in the model were solely based on watching animations for

    avoiding unrealistic lane change behavior by HOV eligible vehicles. Based on watching

    animations, assigning 500= for HOV vehicle type was suitable for realistic lane

    change behavior. Table 1 lists the cost coefficients associated with each trafficcomposition and

    Table 2 summarizes the connector costs defined in the network.

    Table 1.Cost Coefficients for each Traffic Composition

    Traffic Composition/ CostCoefficients

    GP HV HOV

    1 1 1

    0 0 0 0 0 500

    Table 2.Connector Costs

    Connector Type Associated Costs

    GP Lane Connector 5/ mile

    HOV Lane Connector 0/ mile

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    For this study, it is assumed that the cost coefficient values and connector costs

    were well calibrated based on watching animations. Thus, these local parameters were

    not considered during the entire network model calibration.

    For I-95 and I-395 which feature Reversible High Occupancy (RHOV) lanes,

    similar strategy of closing and opening links and lanes was used. In this case HOV 3+

    vehicles were eligible to use the HOV lanes during the peak hours for each direction (NB

    during morning peak, and SB during evening peak).

    Table 3 lists the HOV schedule for the freeways in consideration.

    Table 3. HOV Schedule for Corridors in NOVA Network

    Freeway/Direction HOV Eligibility Hours of Operation

    I-66 EB (Outside Beltway) HOV 2+ 5:30 9:30

    I-66 EB (Inside Beltway) Only HOV 2+ 6:30 9:00

    I-66 WB (Outside Beltway) HOV 2+ 15:00 19:00

    I-66 WB (Inside Beltway) Only HOV 2+ 15:30 18:30

    I-95 and I-395 NB HOV 3+ 6:00 9:00

    I-95 and I-395 SB HOV 3+ 15:30 18:00

    1.4 Toll Roads and Stop Signs

    SH 267 consists of toll roads and toll free roads. Most of the toll booths are

    located on the on- and off-ramps while a few of them are located on the main lines. Stop

    signs have been defined in the network to imitate the toll booths that have cash/credit

    card service as they prevent multiple vehicle entrance at the same time. Dwell times for

    these stop signs follow a normal distribution N (8, 1) for vehicles using Cash lanes. That

    is, the time distribution has a mean of 8 seconds and standard deviation of 1. For vehicles

    using Smart tag lanes, the stop signs follow a normal distribution N (3, 1). Furthermore,

    reduced speed areas were defined on certain lanes of SH 267. Table 4 gives the details of

    the speeds and deceleration values used for these lanes.

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    Table 4.Speed and Deceleration values used for lanes on SH 267

    Name of the RoadNumber of Dedicated

    Smart Card lanes

    Minimum

    Speed (mph)

    Maximum

    Speed (mph)

    Deceleratio

    n (ft/s2)

    DTR 7 30 40 6.562

    Dulles Greenway 4 7 15 6.562

    It must be noted that the speed and deceleration values have been assumed based

    on the information available at the Toll road websites.

    1.5 Driving Behavior Parameters Based on Link Type

    In VISSIM, driving behavior is associated to each link by its link type. Though it

    is possible to define a different driving behavior parameter set for each vehicle type

    within the same link, it has been assumed in this project that rather than vehicle type,

    these parameters are associated to the vehicle position in the network. For example, it

    was observed that some on- ramps on the NOVA network had heavy demand during the

    morning peaks and in reality the mainline vehicles on the right most lanes in the

    acceleration/merge link tend to slow down and yield to the vehicles from the on ramp.

    Thus, driving behavior of vehicles from the on-ramp may be different from those on the

    mainline near the merge section.

    In order to generate this behavior the on-ramp and acceleration links were defined

    as separate type enabling to define and control driving behavior parameters in a manner

    that would make the drivers from the on-ramps more aggressive than the ones on the

    right most lane on the mainline. Some factors that could be adjusted to increase/decrease

    aggressiveness of drivers are the -1 ft/s2 per distance reductions factor, accepted

    deceleration, safety distance reduction factor (SDRF) which are available in VISSIM

    under the Lane Change parameters of the Driving Behavior section. Based on assistance

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    from PTV America staff and test runs, it was observed that altering SDRF values

    influenced the aggressiveness of the drivers, at least increased aggressiveness. By

    defining different link types for the on-ramp acceleration lanes and lowering the SDRF

    values for these links (to around 0.2 against the default value of 0.6), it was possible to

    generate realistic merge behavior on the freeway.

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    Chapter 2: O-D Estimation

    One of key elements in the microscopic simulation modeling process is to

    estimate OD table. OD tables can be either obtained from conventional household

    surveys or estimated using sensor counts from freeway mainlines and on- and off- ramps.

    Given that the cost of collecting OD information from field is so expensive, the OD

    tables for this project were estimated using sensor counts. However, since most of

    available sensors were located on mainline freeway, there was a need to collect on- and

    off-ramp volumes, especially where no sensors are available. Once the mainline and ramp

    volume counts were obtained, QUEENSOD method was used in the estimation of OD

    tables. For the NOVA project, it was required to look into a 15 hour time period (5 AM to

    8 PM), the OD demands were estimated by each hour and a total of 15 OD tables were

    developed for each freeway and direction.

    2.1 Data Collection

    The link volumes required to carry out the OD estimation for all the freeways in

    the NOVA region were collected through the three main sources Detector information

    through the STL Database; Video images accessed at http://vds.trafficland.com and

    AADT data accessed from the VDOT website.

    2.1.1 Data from Detectors

    Mainline volume counts for the freeway were extracted from the STL database. In

    order to do this, it was necessary to know the detector locations and their quality. Initial

    queries were made to retrieve the location information of the detectors such as Interstate

    Direction, Type of Link (Mainline/Off Ramp/On Ramp), and Milepost. For the purpose

    of identifying good detectors, real time screening tests value were used [1, 2]. Real time

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    screening tests values are characteristic to each detector based on the volume and speed

    data that the detector reports, giving a measure of whether the data reported by the

    detector is reasonable or not. Table 5 summarizes the detectors that were identified as

    good ones based on the initial queries.

    Table 5.Detector Data Quality Summery by Interstate

    Interstate Direction No of Reliable Mainline detectors/No of detectors available

    EB 100/190I 66

    WB 108/198

    NB 72/139

    SB 72/133I 95

    Rhov 54/75

    NB 4/59I 395

    SB 4/57

    As mentioned earlier, some of the ramp volume counts were collected from the

    field through video images transmitted by the CCTV cameras administered and

    controlled by the Northern Region Operations. These efforts are explained in the sections

    that follow.

    Once the location and quality of the detectors were known, the average values of

    the six weekday volumes were retrieved from the database. The six weekdays used were

    Tue Thurs over two weeks (i.e., May 8-10, 2007 and May 15-17, 2007). By identifying

    the detectors available on these freeways, specifying the corresponding detector IDs and

    time periods, simple queries in Oracle-SQL Plus were used to retrieve the required

    detector information and traffic volume counts.

    A sample query that was used to retrieve data from the STL database is as follows

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    spool C:\vidya\May\Stn1\496.txt

    select t.time_string ||' '|| min(detectorid)||' '|| sum(volume) ||' '||

    round(avg(volume),2) ||' '|| count (volume)

    from nova.detector_flow df, timex t, calendar c

    where

    t.time_key between 500 and 2000

    and df.detectorid = 496

    and df.time_key = t.time_key

    and df.calendar_key = c.calendar_key

    and c.datex in ('8-May-2007','9-May-2007','10-May-2007','15-May-2007','16-

    May-2007','17-May-2007')

    and screening_tests not like '%0%'

    and screening_tests not like '%9%'

    group by t.time_string

    /

    spool close;

    A list of the detectors with their IDs and corresponding locations that have been used for

    the OD Estimation task of this project has been provided in Table 6, Table 8, Table 10,

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    Table 12,

    Table 14 and

    Table 15.

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    2.1.2 Data from Video Images

    Volume data for the on/off ramps at locations characterized by low qualify

    detector data was collected by accessing video images at http://vds.trafficland.com. These

    videos were recorded and saved using Camtasia software. In order to take advantage of

    the CCTV Cameras, time was first spent to identify the camera locations, camera IDs,

    and to list the ones that would be helpful in the data collection. For this purpose two visits

    were made to the Northern Region Operations TMC in Arlington to obtain detailed

    information about the camera locations and the ramps that can be used in the data

    collection.

    The process of getting the CCTV cameras fixed at the desired locations and

    capturing the images for the required time periods was a challenging task as it demanded

    uninterrupted video capture and good image quality. Data collection was not possible on

    several days in the months of Feb and March 2007 due to very poor video transmission

    from most of the cameras. This issue was resolved by using the upgraded version of the

    trafficland website (accessed at http://vds.trafficland.com) which was available from

    the second week of April 2007. The upgraded system made streamlined videos available

    for the cameras located in NOVA region. The volume counts from the video images were

    reduced manually which was a time consuming task. Table 7, Table 9,

    Table 11 and Table 13 list the locations and the time periods for which the

    volume counts have been reduced from the CCTV cameras.

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    Table 6. I-66 EB Volume Data from Detectors

    LocationLinkID

    Type ofLink

    StationNo Detector ID

    Rte 29 - U 25 ML Stn 1 21-27; 37-43; 53-59; 69 -75; 101-107

    Rte 29 - A 27 ML Stn 2 117-123

    Rte 29 - D 29 ML Stn 3 126 -132

    Rte 28 - A 31 ML Stn 4 144 -150

    Rte 28 - D 33 ML Stn 5 155 -163; 173 179; 189 - 195

    Rte 7100 - A 37 ML Stn 6 205-211; 715-721

    Rte 7100 - D 45 ML Stn 7 235-241

    Rte 50 - A 47 ML Stn 8 263-271

    Rte 50 - D 51 ML Stn 10 302-308

    Rte 243 - U 60 ML Stn 11 338-344

    Rte 243 - A 61 ML Stn 12 617-623

    Rte 243 - D 73 ML Stn 14 413-419; 421-427

    Rte 7 - A 83 ML Stn 19 451-453

    Sycamore - A 91 ML Stn22 455-457

    G mason - A 95 ML Stn 23 466-468

    Table 7. I-66 EB Volume Data from Videos

    Location LinkID Type ofLink RampNo Time Period of data from videos

    Rte 29 - D 28 On R 2 7:00 - 18:00

    Rte 28 - U 30 Off R 3 9:00 - 15:00

    Rte 28 - D 32 On R 4 9:00 - 15:00

    Rte 50 - D 50 On R 11 6:00 - 8:00; 10:00 - 13:00; 14:00 - 15:00

    Rte 123 - U 52 Off R 12 6:00 - 15:00; 16:00 - 18:00

    Beltway - U 74 Off R 22 9:00 - 17:00

    Beltway - A 76 Off R 23 9:00 - 13:00

    Beltway - A 78 Off R 24 11:00 - 13:00

    Rte 7 - D 84 On R 27 6:00 - 14:00; 15:00 - 18:00

    Rte 110 - A 106 On R 37 6:00 - 18:00

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    Table 8. I-66 WB Volume Data from Detectors

    LocationLinkID

    Type ofLink

    StationNo Detector ID

    Before Rte 7 163 ML Stn 2 509-510

    Rte 7 - U 174 On Det 1 538

    Rte 7 - D 176 Off Det 2 537

    Rte 243 - U 187 ML Stn 8 570-576

    Rte 243 - D 199 ML Stn 12 625-631

    Rte 123 - U 203 ML Stn 13 346-352

    Rte 50 - D 212 Off Det 3 687

    Rte 50 - D 213 ML Stn 18 679-681

    Rte 50 - D 214 On Det 4 688

    Rte 50 - D 215 ML Stn 19 243-251

    Rte 7100 - D 221 Off Det 5 710

    Rte 7100 - D 222 Aux Det 6 711

    Rte 28 - U 225 ML Stn 23 702-708; 725-731

    Rte 28 - U 226 ML Stn 24 197-203

    Rte 28 - D 229 Off Det 741

    Rte 28 - D 230 ML Stn 26 733-739

    Rte 29 - U 232 ML Stn 27 134-142

    Rte 29 - U 233 Off Det 7 751

    Rte 29 - U 234 ML Stn 28 743-749

    Rte 29 - U 235 On Det 8 762

    Rte 29 - A 236 ML Stn 29 754-760

    Rte 29 - D 237 On Det 9 752

    Rte 29 - D 242 ML Stn 32 109-115

    Table 9. I-66 WB Volume Data from Videos

    Location Link IDType of

    LinkRamp

    No Time Period of data from videos

    TR Bridge Entry 151 ML M 1 5:00 - 20:00TR Bridge - A 152 Off R 2 5:00 - 20:00

    TR Bridge - D 153 ML M 3 5:00 - 20:00

    Spout run - D 160 On R 4 9:00-12:00; 14:00 - 18:00

    N Sycamore - U 165 ML M 5 10:00 - 18:00

    N Sycamore - D 166 Off R 6 10:00 - 18:00

    Rte 7100 - U 217 Off R 7 6:00 - 10:00; 12:00 - 18:00

    Rte 234 - U 243 Off R 8 6:00 - 13:00

    Rte 234 - D 247 On R 9 9:00 - 13:00

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    Table 10. I-95 NB Volume Data from Detectors

    Location Link IDType of

    Link Station No Detector IDBeginning of

    RHOV 1005Rhov ML

    Stn 1 828

    Rte 234 - U 859 ML Stn 2 813-815

    Rte 234 - A 860 ML Stn 3 816-818

    Rte 234 - A 861 Off Stn 4 1489

    Rte 234 - D 862 ML Stn 5 1483-1485

    Rte 234 - D 864 ML Stn 6 831

    Rte 234 - D 865 On Stn 7 837

    Rte 784 - U 867 ML Stn 8 840-841

    Rte 3000 - U 887 ML Stn 9 893-895Rte 3000 - U 888 Off Stn 10 905

    Rte 3000 - D 896 On Stn 11 914

    Rte 123 - U 897 ML Stn 12 927-931

    Rte 123 - A 899 ML Stn 13 943-944

    Rte 123 - A 900 On Stn 14 946

    Rte 611 - D 904 ML Stn 15 962-964

    Rte 7100 - U 911 Off Stn 16 1032

    Rte 7100 - A 912 ML Stn 17 1028-1030

    Rte 7100 - A 913 On Stn 18 1033

    Rte 7100 - D 916 ML Stn 19 1034-1036

    Rte 7100 - D 917 On Stn 20 1038

    Rte 644 - U 1019 Rhov Off Stn 21 1057Rte 644 - U 1020 ML Stn 22 1329-1335

    Table 11. I-95 NB Volume Data from Videos

    Location Link IDType of

    LinkRamp

    No Time Period of data from videos

    Rte 642 - D 909 On R 26 7:00 - 8:00

    Rte 644 - U 919,920 Off R 31 6:00 - 7:00

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    Table 12. I-395 NB Volume Data from Detectors

    Location Link IDType of

    Link Station No Detector ID

    Rte 648 - A 940 ML Stn 1 1147-1149

    Rte 648 - D 941 On Stn 2 1182

    Rte 236 - D 946 ML Stn 3 1161-1165

    Rte 236 - D 947 On Stn 4 1816

    Rte 420 - U 949 Off Stn 5 1586

    Rte 420 - A 950 ML Stn 6 1181-1183

    Rte 420 - D 951 On Stn 7 1820

    Rte 7 - A 954 ML Stn 8 1184-1185

    Rte 7 - D 957 On Stn 9 1829

    Rte 402 - A 960 ML Stn 10 1200-1203

    Rte 402 - D 965 On Stn 11 1833

    Rte 120 - A 968 ML Stn 12 1204-1207

    Rte 110 - U 1038 Rhov ML Stn 13 1617-1618

    Rte 110 - U 1037 Rhov On Stn 14 1619

    Table 13. I-395 NB Volume Data from Videos

    Location Link IDType of

    LinkRamp

    No Time Period of data from videos

    From I-495 934,935 On R 0 5:00 - 20:00

    Rte 648 - A 939 Off R 2 5:00 - 7:00; 8:00 - 18:00Rte 120 - U 967 Off R 15 5:00 - 20:00

    Rte 27 - U 978 Off R 19 5:00 - 10:00

    Rte 27 - A 976 ML M 19-20 5:00 - 10:00

    Rte 27 - A 1034 Rhov ML R 102 5:00 - 10:00

    Rte 27 - D 972 Off R 20 7:00 - 13:00

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    Table 14. I-95 SB Volume Data from Detectors

    Location Link IDType of

    Link Station No Detector ID

    Rte 644 - D 1416 Rhov Stn 1 1328

    To Rte 617 1204 ML Stn 2 1063-1066

    Rte 7100 - U 1205 ML Stn 3 1047-1050

    Rte 7100 - A 1208 On Stn 4 1355

    Rte 611 - U 1218 ML Stn 5 1405-1407

    Rte 611 - U 1219 Off Stn 6 968

    Rte 611 - A 1220 ML Stn 7 965-967

    Rte 611 - D 1221 On Stn 8 1422

    Rte 123 - U 1223 Off Stn 9 952

    Rte 123 - U 1224 ML Stn 10 953-957

    Rte 123 - A 1225 On Stn 11 1423Rte 123 - D 1226 ML Stn 12 1424-1426

    Rte 123 - D 1227 On Stn 13 1427

    Rte 123 - D 1228 ML Stn 14 933-937

    Rte 3000 - U 1229 Off Stn 15 915

    Rte 3000 - U 1230 ML Stn 16 910-912

    Rte 3000 - D 1233 On Stn 17 1430

    Rte 3000 - D 1234 ML Stn 18 896-899

    Opitz Blvd - U 1237 Off Stn 19 889-890

    Opitz Blvd - A 1245 ML Stn 20 883-885

    Rte 784 - D 1246 ML Stn 21 865-866, 1570

    Rte 234 - U 1440 Rhov On Stn 22 870

    Rte 234 - U 1247 ML Stn 23 843-845Rte 234 - U 1249 Off Stn 24 836

    Rte 234 - U 1250 ML Stn 25 833-835

    Rte 234 - D 1252 ML Stn 26 1486-1488

    Rte 234 - D 1253 On Stn 27 1490

    End of Rhov 1443 Rhov Stn 28 829

    Table 15. I-395 SB Volume Data from Detectors

    Location Link IDType of

    Link Station No Detector ID

    Rte 7 - A 1159 ML Stn 1 1260-1263

    Rte 420 - D 1164 On Stn 2 1882

    Rte 236 - D 1172 On Stn 3 1889

    Rte 236 - D 1416 Rhov Stn 4 1153

    Rte 648 - A 1179 ML Stn 5 1283-1287

    Rte 648 - D 1183 ML Stn 6 1293-1295- A: At the Interchange

    - U: Upstream of the Interchange

    - D: Downstream of the Interchange

    Link ID: Used in the QueensOD estimation input to assign links

    Station No and Ramp No: Used for denoting a location

    Detector ID: IDs as per the STL database

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    2.1.3 Extrapolation of Missing Data

    The data could be retrieved from the database to cover the time period 5 AM to 8

    PM. The data collected from the detectors and video images in several cases did not

    cover the entire time period. For these cases, volume counts were extrapolated from short

    term counts to the entire time period by using the flow profiles of mainline, on- and off-

    ramp volumes of those that covered the entire period. Figure 2, Figure 3 and Figure 4

    show the flow profiles for the mainline, on-ramp and off-ramp of I-66 EB respectively.

    0

    1000

    2000

    3000

    4000

    5000

    6000

    7000

    8000

    0 2 4 6 8 10 12 14 16

    Hour of the Day (5:00 AM - 8:00 PM)

    Vehiclesp

    erHour

    Stn 1

    Stn 3

    Stn 6

    Stn 7

    Stn 5

    Figure 2. I-66 EB Mainline Flow Profiles

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    0

    500

    1000

    1500

    2000

    2500

    3000

    0 2 4 6 8 10 12 14 16

    Hour of the day (5:00 AM - 8:00 PM)

    Vehiclesperhour

    On 4

    On 2

    On 7

    On 8

    On 11

    On 13

    Figure 3. I-66 EB On Ramp Flow Profiles

    0

    200

    400

    600

    800

    1000

    1200

    1400

    1600

    1800

    0 2 4 6 8 10 12 14 16

    Hour of the Day (5:00 AM to 8:00 PM)

    VehiclesperHour

    Off 1

    Off 3

    Off 9

    Off 10

    Off 14

    Figure 4. I-66 EB Off Ramp Flow Profiles

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    Since the sections were fairly long, the variation in the flow profiles could be

    attributed to the locations and the respective nature of demands. The obtained profiles

    were categorized into sections. Thus, the freeway was divided into sections and the flow

    profiles corresponding to a particular section of the freeway were used for the

    extrapolation.

    For example, the video counts for On-ramp 2 did not cover the time period 5:00

    AM 7:00 AM (Figure 4). The flow profile of the On-ramp 4 (closest to On-ramp 2) was

    used to extrapolate the missing data for the time period 5:00 AM 7:00 AM.

    Table 16. Extrapolation of Missing Data

    On-Ramp 2 (initial) missing missing 872On-Ramp 4 1483 1716 1605

    Flow Profile of On 4 (based on 3rd time period) 0.923988 1.069159 1

    On-Ramp 2 (Extrapolated) 806 932 872

    The extrapolated values were further adjusted to balance the flows based on the

    available mainline counts upstream and downstream of the corresponding ramps. Missing

    data and extrapolated data for this particular case is shown in Table 16. Similar

    extrapolation was done to obtain missing counts on the other sections.

    The data collected through the detectors and videos did not cover all the links of

    the NOVA network. To overcome these, AADT data published for year 2006 (accessible

    at http://www.virginiadot.org/info/ct-TrafficCounts-2006.asp ) were used to supplement

    and give an estimation of the volumes of other links. Once an estimate of the total

    volume say x for a particular link was obtained for the 15 hour period from the AADT

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    data, the flow profiles were used to distribute this x for each hour within the 15 hour

    time period.

    2.2 O-D Estimation Using QUEENSOD

    Van Aerde et al. [3] proposed the QUEENSOD model for generating dynamic

    synthetic O-D matrices and also tested it on a 35 km section of Highway 401 in Toronto

    and the Santa Monica Smart Corridor in Los Angeles. Many of the techniques developed

    for estimating O-D matrices from link flow counts are based on very similar but slightly

    different mathematical/statistical properties of the final matrix obtained. In many

    practical applications, it is unclear as to how significant these mathematical/theoretical

    intricacies are in view of the amount and quality of data that must be used as inputs.

    The QUEENSOD model aims at finding an O-D matrix that minimizes the

    discrepancies between estimated and observed link flows. For static O-Ds this approach

    may be mathematically expressed as

    ( )aav

    vvFa

    ,min (2)

    subject to

    10, =a

    ij

    ij

    a

    ijija ppTv

    where

    ( )aa vvF , = function of the general error measurement between av and av ,

    av = observed link flow in linka

    av = estimated link flow in linka

    ijT = estimated trips leaving zone i to zonej

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    a

    ijp = proportion of trips from zone i to zonej traveling through linka,

    i = origin,

    j = destination, and

    a = link identifier

    The QUEENSOD model starts with a seed matrix (uniform or historic matrix) and

    uses this seed matrix to estimate the link flows. Based on quantitative comparisons

    between observed and estimated link flows, adjustments are made on the seed O-D

    matrix. This involves adjusting the seed O-D matrix by calculating error correction

    factors between the actual link volumes and estimated link volumes. The adjusted seed

    O-D matrix is updated in the subsequent iterations to obtain new error correction factors

    until the error between the actual link volumes and estimated link volumes are

    minimized. A more detailed description of this model can be found in [4]. Hourly OD

    matrices for each vehicle type (GP, HOV, HGV) were generated. Table 17 summarizes

    some details on the OD Estimation for each freeway.

    Table 17. Details of OD Matrices for each Freeway

    Interstate Direction Vehicle Types included in OD matrix

    I 66 EB GP, HOV 2+, HVs

    I 66 WB GP, HOV 2+, HVsI 95 and I - 395 NB GP, HOV 3+, HVs

    I 95 and I - 395 SB GP, HOV 3+, HVs

    I 495 EB/WB GP, HVs

    SH 267 EB/WB Cash (GP), E-Z Pass (HOV)GP: General Purpose

    HOV: High Occupancy Vehicle

    HVs: Heavy Vehicles

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    Estimation using QUEENSOD required preparing several input files which are

    explained as follows.

    Feasible OD Pairs This input file consists of the feasible OD pairs for a particular

    corridor and each of the pair was assigned a unique number to be referenced by the

    QUEENSOD during the estimation process

    Minimum Path Trees This input file is related to the sequence of links that make up the

    path for a particular OD pair. For example, if the path tree for a particular OD pair is as

    follows.

    6601-6606: 25 26 27 28

    This denotes a path for the OD pair 6601 6606 and vehicles will take the path

    consisting of the link sequence 25, 26, 27 and 28. Since the NOVA network did not have

    multiple paths, it was fairly easy to come up with the path trees and these were done

    manually.

    Link Volume This input file consists of volume data for each link that will be used in

    the OD estimation process by identifying the possible OD pair and the link sequence or

    path tree for the same.

    Once the required input files for the corridor was prepared, QUEENSOD

    algorithm coded in MATLAB was used to come up with the corresponding OD tables.

    QUEENSOD is an iterative method that tries to balance the link volumes across the paths

    for the various OD pairs. The number of iterations used during the OD estimation process

    was 100.

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    2.3 Measures of Effectiveness Data Collection

    Field travel time data collected in January 9 through 11, 2007 and May 25

    through 30, 2007 were prepared for sections on I-66, I-95 and I-395 of the NOVA

    network and used for the calibration purpose. Detector counts and speeds for the

    corresponding days in January and May 2007 were retrieved from the STL database and

    used in an effort to look at multiple MOEs during the calibration process.

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    Chapter 3: Simulation Model Calibration

    3.1 IntroductionThis chapter explains the application and results of the experimental design

    approach using Latin Hypercube Sampling (LHS) method for calibration of a portion of

    I-66 Eastbound of the NOVA network modeled in VISSIM. Figure 5 depicts the steps

    that were performed in an effort to obtain most suitable combination of driving behavior

    parameters for the developed model using experimental design procedure.

    Figure 5. Flow Chart for Calibration Using Latin Hypercube Experimental Design

    Simulation Model Setup

    Initial Evaluation

    Experimental Design(LHD)

    Adjust Key ParameterRanges (such as SDRF)

    Evaluation of the CalibratedParameter Set

    (Carry out morereplications with selected

    parameter set)

    End

    Unsatisfied

    Satisfied

    Yes

    No

    Satisfied

    Parameter SelectionBased on Multiple MOEs(TT, Counts and Speeds)

    SatisfactoryMOEs?

    Unsatisfied

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    3.2 Latin Hypercube Sampling

    Latin Hypercube Sampling (LHS) [5] is a statistical method that is used to

    generate a distribution of plausible collections of parameter values from a

    multidimensional distribution. A simple method to generate n combination sets of k

    variables is to use random sampling. An alternate method to generate them would be to

    use stratified sampling, which can characterize the population of each variable equally

    well as random sampling with a smaller sample size.

    In stratified sampling of a single variable X1, the distribution of X1 is divided into

    m segments. The distribution of n samples over these segments is proportional to the

    probabilities of X1 falling in the segments. Each sample is drawn from its segment by

    simple random sampling and maximum stratification takes place when the number of

    segments m equals the number of samples n required.

    For a multi variable case (generating n combination sets of k variables X1,

    X2Xk), an efficient sample is the one that is maximally stratified for all the variables

    simultaneously. That is, the range of each variable is divided into n non-overlapping

    intervals on the basis of equal probability, and one value from each interval is randomly

    selected. The n values obtained for X1 are randomly paired with n values of X2. These n

    pairs are then combined in a random manner with n values of X3 to form n triplets and so

    on. Thus, nk-tuplets can be formed in this fashion (Latin Hypercube Samples). These

    samples can be thought of as forming an input matrix of order (n x k) where the

    combination set in the ith

    row containing values for k input variables can be used as input

    of ith run of a computer model.

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    A Two-Dimensional representation of One Possible Latin Hypercube Sample of

    Size 5 for X1 and X2 is shown in Figure 6.

    Figure 6.Two-dimensional representation of a LHS of size 5 for X1 and X2

    3.3 Experimental Design Results

    As a part of the project, the site and time period chosen for the initial calibration

    efforts for the NOVA network is I-66 Eastbound from Rte 15, Gainesville to I-495

    Beltway (just after Rte 243) from 5:00 AM to 8:00 AM. This is a 23.5 mile section of the

    freeway that is heavily congested in the morning. During the remainder of this chapter,

    this portion of I-66 Eastbound has been referred to as I-66 EB network. The network

    alignment for I-66EB network is shown in Figure 7.

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    Figure 7. I-66EB Network

    3.3.1 Simulation Model Setup

    The 23.5 mile section of I-66 EB freeway was coded in VISSIM (a part of the

    NOVA network coded in VISSIM), and the traffic data for the time period 5:00 AM

    8:00 AM (O-D estimates using QUEENSOD method) were input into the model.

    3.3.2 Initial Evaluation

    In order to test if the default values for the driver behavior parameters in VISSIM

    were sufficient to generate field conditions, 25 replications were conducted for the

    network. The travel time simulation outputs based on 5 replications have been shown in

    Figure 8, Figure 9 and Figure 10. Since the probe vehicles that were used to collect the

    travel time from the field traveled on General Purpose (GP) lanes of the I-66 EB network,

    the simulated travel times corresponding to GP vehicle type were used in the analysis.

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    The default parameters did not represent the field conditions, especially with the

    3rd time period TT. Moreover, volume counts were low through out the simulation period.

    Comparison of volume counts and speeds from simulations and detectors have been

    presented in Figure 11, Figure 12, Figure 13 and Figure 14 for two stations namely

    station 2 and station 10. Thus it was necessary to conduct the other steps proposed in the

    calibration procedure. It must be noted that the first 15 minutes of the simulation was

    considered as warm up time and MOEs were collected from 5:15 AM onwards, for every

    15 minutes.

    0

    100

    200

    300

    400

    500

    600

    700

    800

    550 600 650 700 750 800 850 900

    Travel Time (seconds)

    Frequenc

    y

    Figure 8. Simulated TT Vs Observed TT (6:00-6:30 AM)-Default Parameters

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    0

    50

    100

    150

    200

    250

    300

    550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250

    Travel Time (seconds)

    Frequency

    Figure 9. Simulated TT Vs Observed TT (6:30-7:00 AM)-Default Parameters

    0

    50

    100

    150

    200

    250

    550

    600

    650

    700

    750

    800

    850

    900

    950

    1000

    1050

    1100

    1150

    1200

    1250

    1300

    1350

    1400

    1450

    1500

    1550

    1600

    1650

    Travel Time (seconds)

    Frequency

    Figure 10. Simulated TT Vs Observed TT (7:30-8:00 AM)-Default Parameters

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    0

    200

    400

    600

    800

    1000

    1200

    1400

    1600

    1800

    2000

    2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Numberofvehicles Default_1

    Default_2

    Default_3

    Default_4

    Default_5

    May 25th Det data

    Jan 10th Det Data

    Figure 11. Simulated Counts Vs Detector Counts for Station 2-Default Parameters

    0

    10

    20

    30

    40

    50

    60

    70

    80

    900 1800 2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Speedinmph

    Default_1

    Default_2

    Default_3Default_4

    Default_5

    May 25th Det speed

    Jan 10th Det Data

    Figure 12. Simulated Speed Vs Detector Speed for Station 2-Default Parameters

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    0

    200

    400

    600

    800

    1000

    1200

    1400

    1600

    1800

    2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Numberofvehicles Default_1

    Default_2

    Default_3

    Default_4

    Default_5

    May 25thDet data

    Jan 10th Det Data

    Figure 13. Simulated Counts Vs Detector Counts for Station 10-Default Parameters

    0

    10

    20

    30

    40

    50

    60

    70

    900 1800 2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Speedinmph

    Default_1

    Default_2

    Default_3

    Default_4Default_5

    May 25th det speed

    Jan 10th Det Data

    Figure 14. Simulated Speed Vs Detector Speed for Station 10-Default Parameters

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    Relative errors (based on 25 replications from simulation for default parameters) for

    travel time speeds and counts have been summarized in Table 18.

    Table 18. Relative Error for Simulations using Default Parameters

    Relative Error Default

    TT Error (3rd Time period) 1.35

    Counts Error (Stn 2) 0.205

    Speed Error (Stn 2) 0.36

    Counts Error (Stn10) 0.156

    Speed Error (Stn 10) 0.188

    3.3.3 Initial Calibration Latin Hypercube Design (LHD) for Driving Behavior

    The initial set of parameters that were identified as relevant to the performance of

    the simulation model with their acceptable ranges are as follows:

    1) Waiting time before diffusion (seconds): 30-90

    2) Min. Headway (front/rear, meters): 0.1-0.9

    3) Max. Deceleration Own vehicle Freeway link (m/s2): -5.00 ~ -1.00

    4) Reduction Rate (meters per 1m/s2) Own vehicle Freeway link: 20-80

    5) Accepted Deceleration (m/s2) Own vehicle Freeway link: -3.0 ~ -0.2

    6) Max. Deceleration Trailing vehicle Freeway link (m/s2): -5.00 ~ -1.00

    7) Reduction Rate (meters per 1m/s2) Trailing vehicle Freeway link: 20-80

    8) Accepted Deceleration (m/s2) Trailing vehicle Freeway link: -3.0 ~ -0.2

    9) Number of observed preceding vehicles: 1 5

    10) Maximum look ahead distance (meters): 200 300

    11) CC0: average standstill distance (meters): 1.0 2.0

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    12) CC1: headway at a certain speed (seconds): 0.5 3.0

    13) CC2: longitudinal oscillation (meters): 0 ~ 15.0

    14) CC3: start of deceleration process (seconds): -30.0 0

    15) CC4: minimal closing v (m/s): -1.0 ~ 0

    16) CC5: minimal opening v (m/s): 0.0 ~ 1.0

    17) CC6: dv/dx (10-4

    rad/s): 0.0 ~ 20.0

    18) CC7: car following activities b (m/s2): 0.0 ~ 1.0

    19) CC8: acceleration behavior when starting (m/s2): 1.0 ~ 8.0

    20) CC9: acceleration behavior at v ~ 80 km/h (m/s2): 0.5 ~ 3.0

    21) Speed Index 1 (mph): 1 ~ 3 (55 ~ 65, 65 ~ 72.5, 65 ~ 75)

    22) Speed Index 2 (mph): 1 ~ 3 (60 ~ 70, 65 ~ 72.5, 65 ~ 75)

    23) Speed Index 1 (mph): 1 ~ 2 (65 ~ 75, 65 ~ 72.5)

    24) Max. Deceleration Own vehicle Ramp Merge Link (m/s2): -5.00 ~ -1.00

    25) Reduction Rate (meters per 1m/s2) Own vehicle Ramp Merge Link: 20-80

    26) Accepted Deceleration (m/s2) Own vehicle Ramp Merge Link: -3.0 ~ -0.2

    27) Max. Deceleration Trailing vehicle (m/s2) Ramp Merge Link: -5.00 ~ -1.00

    28) Reduction Rate (meters per 1m/s2) Trailing vehicle Ramp Merge Link: 20-80

    29) Accepted Deceleration (m/s2) Trailing vehicle Ramp Merge Link: -3.0 ~ -0.2

    Parameters 21, 22 and 23 set desired speed distributions along the I-66 EB

    network based on their locations where three different posted speed limits are present.

    These were indexed for the convenience of experimental design. Thus, speed index 1 and

    2 have 3 options to define the desired speed distribution on the freeway where the posted

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    speed limits are 55 mph and 60 mph respectively. Speed index 3 has two options to

    define the desired speed distribution where the posted speed limit is 65 mph.

    The initial ranges for the lane change and car following parameters were obtained

    from [6]. Definitions of these parameters and their functioning in VISSIM can be

    obtained from [7]. As mentioned earlier, the Safety Distance Reduction Factor (SDRF)

    defined for the links plays an important role in altering the aggressiveness of the drivers

    especially near the ramp merge areas. Based on the initial test runs for the I-66 EB

    network, the SDRF values for the freeway link and ramp merge link were fixed to 0.6 and

    0.2 respectively during the experimental design.

    3.3.3.1 Experimental Design Latin Hypercube Sampling

    300 combination sets/samples of the 29 parameters were generated using Latin

    Hypercube Sampling coded in MATLAB.

    3.3.3.2 Multiple Runs

    Five replications for each of the 300 cases were conducted in VISSIM, for a total

    of 1,500 runs. For these runs, the aggregated travel times for specific sections were

    collected. From the five replications for each case, the weighted average travel time

    (based on the number of vehicles) for each case was calculated for three different time

    periods: 6:00 AM 6:30 AM, 6:30 AM 7:00 AM, 7:30 AM 8:00 AM. Simulated

    counts and speeds for station 2 and station 10 were compared with those from the

    detector.

    3.3.3.3 Parameter Set Selection

    The weighted average travel time for GP vehicles (based on number of vehicles

    passing the section) over the 5 replications for each parameter set was calculated. The

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    absolute error of this weighted average against the field travel time for each of the 3 time

    periods was calculated. Similarly, for volume counts and speeds the average of absolute

    error (between 6:00-8:00) over the 5 replications was calculated. Normalization for the

    three measures was done by taking logarithm of these absolute errors. Thus, sum of the

    logarithms of the error in travel time for each time period; logarithm of the average

    absolute error in counts and for each station was determined for comparison.

    Based on looking at the errors for all the MOEs together, the sample case C98

    was selected from the LHD samples. An X-Y plot of the weighted average travel time of

    GP vehicles against the Sample case is shown in Figure 15.

    0

    500

    1000

    1500

    2000

    2500

    0 50 100 150 200 250 300

    Sample Case

    SimulatedTT(WeightedAveragefor5:00-8:00AM)

    Figure 15.Simulated TT Vs Sample Case

    C98

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    Figure 16 shows the variation of the simulated TT with the key parameter CC1

    which has a significant impact on the capacity and hence the performance of a network.

    0

    0.5

    1

    1.5

    2

    2.5

    3

    3.5

    0 500 1000 1500 2000 2500

    Simulated TT in seconds (Weighted Average for 3 hour time period)

    CC1

    (seconds)

    Figure 16. Simulated TT Vs CC1

    25 replications for sample case C98 were carried out and the relative errors

    between the simulated and field measures have been summarized in Table 19.

    Table 19.Relative Error for Simulations using C98 and Default Parameters

    Relative Error C98 Default t-test (p value)

    TT Error (3rd timeperiod)

    0.247 1.35 7.4 * 10 -27

    Counts Error (Stn 2 ) 0.119 0.205 1.4 * 10 -20

    Speed Error (Stn 2) 0.15 0.36 2 * 10 -15

    Counts Error (Stn 10) 0.09 0.156 8 * 10 -25

    Speed Error (Stn 10) 0.09 0.188 5 * 10 -7

    C98

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    It must be noted that the t-test (p value) only show that the distributions of the

    measures obtained for C98 and default parameters are significantly different. However,

    the t-test results do not prove that C98 is a better parameter set for the model. By

    comparing the distributions of the measures obtained from simulation (using sample case

    C98) with those obtained from the field, it was found that the sample case C98 was far

    better than the default parameters. Based on the 5 replications for sample case C98,

    Figure 17, Figure 18 and Figure 19 depict the travel time distribution from simulations

    and field observations. Figure 20, Figure 21, Figure 22 and Figure 23 depict the count

    and speed data from simulations and field.

    0

    100

    200

    300

    400

    500

    600

    700

    800

    550 600 650 700 750 800 850 900

    Travel Time (seconds)

    Frequency

    Figure 17. Simulated TT Vs Observed TT (6:00-6:30 AM)-C98 (LHD_1)

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    0

    50

    100

    150

    200

    250

    300

    350

    400

    550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250

    Travel Time (seconds)

    Frequency

    Figure 18. Simulated TT Vs Observed TT (6:30-7:00 AM)-C98 (LHD_1)

    0

    50

    100

    150

    200

    250

    300

    350

    400

    550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250

    Travel Time (seconds)

    Frequency

    Figure 19. Simulated TT Vs Observed TT (7:30-8:00 AM)-C98 (LHD_1)

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    0

    200

    400

    600

    800

    1000

    1200

    1400

    1600

    1800

    2000

    2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Numberofvehicles C98_1

    C98_2

    C98_3

    C98_4

    C98_5

    May 25th Det data

    Jan 10th Det Data

    Figure 20. Simulated Counts Vs Detector Counts for Station 2 C98 (LHD_1)

    0

    10

    20

    30

    40

    50

    60

    70

    80

    900 1800 2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Speedinmph

    C98_1

    C98_2

    C98_3C98_4

    C98_5

    May 25th Det speed

    Jan 10th Det Data

    Figure 21. Simulated Speed Vs Detector Speed for Station 2 C98 (LHD_1)

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    0

    200

    400

    600

    800

    1000

    1200

    1400

    1600

    1800

    2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Numberofvehicles C98_1

    C98_2

    C98_3

    C98_4

    C98_5

    May 25thDet data

    Jan 10th Det Data

    Figure 22. Simulated Counts Vs Detector Counts for Station 10 C98 (LHD_1)

    0

    10

    20

    30

    40

    50

    60

    70

    900 1800 2700 3600 4500 5400 6300 7200 8100 9000 9900 10800

    Simulation time in seconds (5:30-8:00 AM)

    Speedinmph

    C98_1

    C98_2

    C98_3

    C98_4C98_5

    May 25th det speed

    Jan 10th Det Data

    Figure 23. Simulated Speed Vs Detector Speed for Station 10 C98 (LHD_1)

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    Table 20 draws a comparison of the parameter set selected in the LHD with those

    of the default values.

    Table 20. C98 and Default Parameters

    LHS C98 DefaultDiffusion 56.9 60

    Min Headway 0.355 0.5

    Max Decel -Own (F) -2.38 -4

    Reduction Rate-Own(F) 46.7 200

    Accepted Decel-Own

    (F) -0.275 -1

    Max Decel-T (F) -4.62 -3

    Reduction Rate-T (F) 74.5 200

    Accepted Decel-T (F) -1.194 -0.5

    #obs veh 4 2

    Max Lookahead 253.5 250

    CC0 1.768 1.5

    CC1 0.729 0.9

    CC2 5.225 4CC3 -16.25 -8

    CC4 -0.01167 -0.35

    CC5 0.01167 0.35

    CC6 4.9 11.44

    CC7 0.948 0.25

    CC8 3.718 3.5

    CC9 2.3375 1.5DS1 3 -

    DS2 2 -

    DS3 1 -

    SDRF (F) 0.6 0.6

    Max Decel-Own (M) -1.5 -4

    Reduction Rate-Own

    (M) 30.5 200

    Accepted Decel-Own

    (M) -0.7579 -1

    Max Decel-T (M) -2.2733 -3

    Reduction Rate-T (M) 56.3 200

    Accepted Decel-T (M) -0.6433 -0.5

    SDRF (M) 0.2 0.6

    F Freeway Section, M Ramp Merge Section

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    It was found that the driving behavior parameters from sample C98 generated

    field conditions with respect to travel times for I-66WB, I-95 and I-395 as well. Since no

    field measures were available for I-495 and SH267, animations of the simulations using

    C98 as driving behavior parameter set were watched. Thus, this particular combination

    set was chosen as calibrated set for the NOVA network.

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    Chapter 5: Measures of Effectiveness from the Calibrated Model

    In order to obtain base measures of effectiveness for each corridor of the NOVA

    network, 25 replications with the calibrated driving behavior parameter set were made.

    The following lists the measures that were obtained from the simulation runs.

    5.1 Counts and Speeds

    For each corridor, simulated counts and speeds were obtained for every 15

    minutes and for certain stations that were defined in the VISSIM station. These stations

    have been listed in Table 1. The speed values obtained from the simulations are measured

    in mph.

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    Table 21. Stations defined for Simulated Counts and Speeds

    Station Number Route/Direction Location

    1 I-66 EB Rte 234

    2 I-66 EB Rte 50

    3 I-66 EB Beltway (I-495)

    4 I-66 EB TR Bridge

    5 I-66 WB TR Bridge

    6 I-66 WB Beltway (I-495)

    7 I-66 WB Rte 50

    8 I-66 WB Rte 234

    9 I-95/I-395 NB Rte 619/Triangle

    10 I-95/I-395 NB Dale City

    11 I-95/I-395 NB I-495 Interchange12 I-95/I-395 NB Rte 27

    13 I-95/I-395 SB Rte 27

    14 I-95/I-395 SB I-495 Interchange

    15 I-95/I-395 SB Dale City

    16 I-95/I-395 SB Rte 619/Triangle

    17 I-495 EB/SB Rte 191

    18 I-495 EB/SB I-66 (Beltway)

    19 I-495 EB/SB I-95/I-395

    20 I-495 EB/SB Rte 1

    21 I-495 WB/NB Rte 1

    22 I-495 WB/NB I-95/I-39523 I-495 WB/NB I-66 (Beltway)

    24 I-495 WB/NB Rte 191

    25 SH 267 EB Rte 7

    26 SH 267 EB Dulles Airport Access Rd (DAAR)

    27 SH 267 EB I-66

    28 SH 267 WB I-66

    29 SH 267 WB Dulles Airport Access Rd (DAAR)

    30 SH 267 WB Rte 7

    5.2 Travel Time and Delays

    Based on the travel time sections defined, VISSIM calculates the time taken (in

    seconds) by vehicles to cross the particular section for the time interval specified. The

    travel time sections defined for each corridor are listed in Table 22. Based on the travel

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    time sections defined in VISSIM, the delays (in seconds) for every chosen time interval is

    calculated.

    Table 22. Travel Time Sections Defined in the Network

    Travel Time Section Number Route/Direction Location

    1 I-66 EB Rte 234 to Rte 50

    2 I-66 EB Rte 50 to Beltway

    3 I-66 EB Beltway to TR Bridge

    4 I-66 WB TR Bridge to Beltway

    5 I-66 WB Beltway to Rte 50

    6 I-66 WB Rte 50 to Rte 234

    7 I-95/I-395 NB Rte 619 to Dale City

    8 I-95/I-395 NB Dale City to I-495

    9 I-95/I-395 NB I-495 to Rte 27

    10 I-95/I-395 SB Rte 27 to I-495

    11 I-95/I-395 SB I-495 to Dale City

    12 I-95/I-395 SB Dale City to Rte 619

    13 I-495 EB/SB Rte 191 to I-66

    14 I-495 EB/SB I-66 to I-95/I-395

    15 I-495 EB/SB I-95/I-395 to Rte 1

    16 I-495 WB/NB Rte 1 to I-95/I-395

    17 I-495 WB/NB I-95/I-395 to I-6618 I-495 WB/NB I-66 to Rte 191

    19 SH 267 EB Rte 7 to DAAR

    20 SH 267 EB DAAR to I-66

    21 SH 267 WB I-66 to DAAR

    22 SH 267 WB DAAR to Rte 7

    5.3 Density

    Density for certain links were obtained on each corridor. The location and

    corresponding link IDs for which densities were collected have been shown in

    Table 23.

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    Table 23. Link IDs/Locations for Density

    Link ID Route/Direction Location

    2005 I-66 EB Rte 234

    1601 I-66 EB Rte 50

    1517 I-66 EB Beltway (I-495)

    1326 I-66 EB TR Bridge

    1325 I-66 WB TR Bridge

    1513 I-66 WB Beltway (I-495)

    1605 I-66 WB Rte 50

    1687 I-66 WB Rte 234

    1504 I-95/I-395 NB Rte 619/Triangle1383 I-95/I-395 NB Dale City

    944 I-95/I-395 NB I-495 Interchange

    1948 I-95/I-395 NB Rte 27

    1959 I-95/I-395 SB Rte 27

    945 I-95/I-395 SB I-495 Interchange

    1390 I-95/I-395 SB Dale City

    1501 I-95/I-395 SB Rte 619/Triangle

    732 I-495 EB/SB Rte 191

    84 I-495 EB/SB I-66 (Beltway)

    900 I-495 EB/SB I-95/I-395

    1871 I-495 EB/SB Rte 11851 I-495 WB/NB Rte 1

    905 I-495 WB/NB I-95/I-395

    61 I-495 WB/NB I-66 (Beltway)

    742 I-495 WB/NB Rte 191

    714 SH 267 EB Rte 7

    477 SH 267 EB Dulles Airport Access Rd (DAAR)

    133 SH 267 EB I-66

    134 SH 267 WB I-66

    446 SH 267 WB Dulles Airport Access Rd (DAAR)

    713 SH 267 WB Rte 7

    25 replications for each corridor were made with the calibrated parameter set for

    the 15 hour time period (5AM to 8PM) and the measures (counts, speeds, travel times,

    delays and densities) were obtained for every 15 minutes. The average over these

    replications for each corridor was calculated and has been presented as base measures of

    effectiveness in Appendix A.

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    Chapter 6: Conclusions and Recommendations

    The development of microscopic based traffic simulation model for the NOVA

    Freeway system using VISSIM involved three main tasks: network coding, data

    collection and O-D estimation and calibration. During the development of the model a lot

    of time was spent on data collection and calibration efforts. Based on project study, the

    following conclusions were made

    (1) Default parameters in VISSIM did not simulate realistic behavior for the network

    considered.

    (2) Use of travel time alone as a measure for evaluating parameter sets from the

    experimental design led to the selection of model parameters that did not generate

    realistic outputs for other measures such as counts and speeds.

    (3) The Safety distance reduction Factor (SDRF) that influenced the aggressiveness of the

    drivers on the acceleration links near the on-ramps played a crucial role in generating

    realistic ramp merge behavior. Since the network considered in this study consisted of

    several on-ramps with high volumes, this parameter became crucial for the networks

    performance.

    Based on this study, the application of experimental design approach using Latin

    Hypercube Sampling is recommended for the calibration of microscopic simulation

    models. Use of multiple measures for evaluating the parameter sets from the

    experimental design is also recommended.

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    References

    [1] Real-time screening tests recommended for the NOVA detector data, STL DatabaseDocuments

    [2] Turner, S., Margiotta, R., and Lomax, T.Monitoring Urban Freeways in 2003:

    Current Conditions and Trends from Archived Operations Data. December 2004.

    [3] Van Aerde, M., B. Hellinga and G. MacKinnon. QUEENSOD: A Method for

    Estimating Time Varying Origin-Destination Demands For Freeway

    Corridores/Networks. Presented at Annual TRB Meeting, Washington D.C., January

    1993.

    [4] Park, B. B. and I,Yun. Development of ITS Evaluation Test-Bed Using Microscopic

    Simulation City of Hampton Case Study. Research Report No. UVACTS-15-0-45,

    2003.

    [5] Wyss, D. G. and K. H. Jorgensen.,A Users Guide to LHS: Sandias Latin hypercubeSampling Software. Sandia National Laboratories, Albuquerque, 1998.

    [6] VISSIM User Manualversion 4.30. PTV Planung Transport Verkehr AG,

    Karlsruhe, Germany, 2007.

    [7] Park, B. and J. Won,Microscopic Simulation Model Calibration and Validation

    Handbook, Virginia Transportation Research Council, June 2006.

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    Appendix A

    MOEs for I-66 EB Table 24.Simulated Counts for I-66 EB

    1 2 3 4Time Period/

    Station Number Mean StDev Mean StDev Mean StDev Mean StDev

    5:15 1205.14 9.5 1119.86 11.21 962 18.33 311.79 5.43

    5:30 1326.86 70.57 1237.43 44.55 1057.07 49.75 578.36 10.55

    5:45 1196.36 93.38 1059.79 38.34 1014.21 50.77 592.07 12.82

    6:00 1177.21 91.11 1087.36 79.32 1028.86 43.75 584.64 13.9

    6:15 1277.93 79.77 1199 71.34 1220.5 63.08 674.79 26.79

    6:30 1237.21 88.18 1409.29 59.9 1426.36 69.03 649.29 31.76

    6:45 1217.57 88.46 1460.79 96.38 1336.79 90.69 648.57 30.28

    7:00 1202.71 69.93 1532.5 73.89 1346.86 94.64 633 26.69

    7:15 1279.29 77.73 1422.79 80.91 1416.29 97.17 635 19.28

    7:30 1256.36 99.62 1381.71 59.09 1359.79 90.79 589.07 20.687:45 1230 91.52 1331.57 49.21 1363.43 95.15 551.14 20.69

    8:00 1263.93 84.92 1314.57 94.48 1335.43 90.87 538.57 26.4

    8:15 1123.21 87.74 1372.36 79.91 1328.71 77.16 561.71 21.59

    8:30 1214.21 124.67 1329.21 74.42 1220.07 63.75 684.79 33.02

    8:45 1260.57 86.25 1338.07 29.02 1300.29 72.09 718.71 16.87

    9:00 1269.5 79.33 1302.86 32.07 1251.93 51.34 724.57 20.71

    9:15 1149.21 63.22 1331.57 29.58 1250.79 45.31 723.29 37.97

    9:30 1182.43 82.35 1308.64 48.17 1259.36 45.06 706.64 26.52

    9:45 1218.64 99.04 1292.86 58.53 1200.71 39.11 703.71 35.1

    10:00 1261.29 94.02 1152.29 40.78 968.43 47.95 734.71 26.21

    10:15 999.2 9.5 1073.4 9.5 1211.12 18.33 414.84 5.43

    10:30 1028.3 70.57 1168.4 70.57 1427.43 49.75 689.94 10.55

    10:45 1069.2 93.38 1184.65 93.38 869.46 50.77 682.63 12.82

    11:00 963.4 91.11 1074.33 91.11 846.88 43.75 709.8 13.9

    11:15 1037.5 79.77 1179.5 79.77 969.98 63.08 647.4 26.79

    11:30 925.6 88.18 1225.65 88.18 717.54 69.03 677.43 31.76

    11:45 915.4 88.46 1092.6 88.46 869.98 90.69 703.2 30.28

    12:00 886.6 69.93 1160.3 69.93 966.5 94.64 674.25 26.69

    12:15 920.33 77.73 1100.6 77.73 727.43 97.17 692.74 19.28

    12:30 872.6 99.62 1067.2 99.62 970.65 90.79 643.93 20.68

    12:45 876.6 91.52 1003.1 91.52 821.54 95.15 695.94 20.69

    13:00 804.7 84.92 1093.2 84.92 808.21 90.87 605.62 26.4

    13:15 871.7 87.74 1067.5 87.74 1053.76 77.16 659.54 21.59

    13:30 806.4 124.67 1039.6 124.67 1276.53 63.75 619.8 33.02

    13:45 830.7 86.25 1041.1 86.25 1177.02 72.09 600.5 16.8714:00 899.6 79.33 1057.65 79.33 895.81 51.34 602.4 20.71

    14:15 848.3 63.22 1076.7 63.22 1097.3 45.31 657.2 37.97

    14:30 825.5 82.35 1079.9 82.35 1117.6 45.06 665.8 26.52

    14:45 956.3 99.04 1066.4 99.04 1267.5 39.11 579.23 35.1

    15:00 863.6 94.02 1157.6 94.02 1320.9 47.95 609.76 26.21

    15:15 912.2 9.5 1106.22 9.5 1255.3 18.33 626.45 5.43

    15:30 881.6 70.57 1039.67 70.57 1241.2 49.75 593.92 10.55

    15:45 799.2 93.38 1048.6 93.38 1335.4 50.77 596.64 12.82

    16:00 902.24 91.11 1052.21 91.11 1211.33 43.75 639.56 13.9

    16:15 859.5 79.77 1078.65 79.77 1299.44 63.08 644.76 26.79

    16:30 892.6 88.18 1096.32 88.18 1387.32 69.03 698.93 31.76

    16:45 865.6 88.46 1116.6 88.46 1435.71 90.69 587.53 30.28

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    17:00 865.2 69.93 1042.3 69.93 1283.51 94.64 597.92

    17:15 914.5 88.46 1107.6 70.57 1281.42 90.69 617.64 9.5

    17:30 870.5 69.93 1062.77 93.38 1450.64 94.64 609.83 70.57

    17:45 965.1 77.73 1121.8 91.11 1413.32 97.17 623.84 93.3818:00 837.6 99.62 1071.23 79.77 1277.84 90.79 662.55 91.11

    18:15 918.4 91.52 1116.6 88.18 1134.64 95.15 639.74 79.77

    18:30 818.6 84.92 1008.7 88.46 1142.84 90.87 629.84 88.18

    18:45 792.55 87.74 1011.8 69.93 1218.99 77.16 561.64 88.46

    19:00 811.78 124.67 1030.2 77.73 1086.94 63.75 590.34 69.93

    19:15 765.65 86.25 908.8 99.62 1214.94 72.09 593.77 77.73

    19:30 625.65 79.33 854.9 91.52 1149.64 51.34 609.83 99.62

    19:45 664.67 63.22 844.2 84.92 1282.83 45.31 632.53 91.52

    20:00 642.76 82.35 843.65 70.57 1304.92 45.06 588.66 84.92

    Table 25.Simulated Speeds for I-66 EB

    1 2 3 4Time Period/

    Station Number Mean StDev Mean StDev Mean StDev Mean StDev

    5:15 65.94 1.08 62.47 1.65 57.99 1.09 47.30 0.06

    5:30 60.94 2.81 43.98 6.28 56.79 1.45 46.16 1.03

    5:45 62.38 3.22 14.18 1.01 57.56 1.35 46.56 1.33

    6:00 62.11 3.85 13.99 1.36 57.29 1.48 46.24 2.59

    6:15 60.53 3.81 15.65 1.26 44.01 1.41 46.66 1.18

    6:30 61.44 3.22 19.44 1.36 36.84 3.45 45.51 3.03

    6:45 60.76 3.56 21.69 1.94 29.19 9.82 45.89 2.44

    7:00 60.96 3.04 26.53 4.31 25.46 9.13 46.11 1.51

    7:15 57.26 8.71 32.22 10.74 24.69 7.14 45.09 2.84

    7:30 58.62 9.81 38.66 6.34 21.86 6.87 23.81 23.827:45 60.54 3.49 36.63 8.63 19.56 4.29 46.41 2.12

    8:00 59.34 3.01 26.31 8.62 18.47 2.09 46.65 1.35

    8:15 62.36 3.52 24.1 5.05 17.53 1.54 45.80 2.74

    8:30 62.29 2.34 35.32 8.25 15.88 1.01 44.97 2.21

    8:45 61.24 2.48 47.66 6.87 18.07 2.02 42.94 3.20

    9:00 61.13 2.6 45.39 5.54 16.72 1.23 42.26 2.80

    9:15 62.78 1.25 41.17 7.56 16.59 1.22 43.23 2.11

    9:30 63.16 1.87 41.85 8.6 16.86 1.19 41.24 3.37

    9:45 62.56 1.87 42.36 10.58 15.59 1.08 41.14 3.73

    10:00 62.93 1.69 30.49 15.81 12.05 0.89 42.98 3.04

    10:15 68.1 1.48 63.1 1.36 45.6 4.29 47.2 2.44

    10:30 67 1.41 37.1 1.26 37.5 2.09 46.9 1.51

    10:45 67.2 3.45 17.3 1.36 10.2 1.54 47.1 2.8411:00 68 9.82 16.4 1.94 10.9 1.01 47 23.82

    11:15 67.1 9.13 18.8 4.31 11.3 2.02 47 2.12

    11:30 67.6 7.14 18.5 10.74 8.4 1.23 47 1.35

    11:45 67.8 6.87 43.7 6.34 10.8 1.22 46.9 2.74

    12:00 67.9 4.29 61 8.63 12.4 1.19 47.1 2.21

    12:15 67.5 2.09 59.5 8.62 8.9 1.08 47.1 3.20

    12:30 68.1 1.54 64.6 5.05 11.6 0.89 47 2.80

    12:45 68 1.01 64.9 8.25 9.9 4.29 47 2.11

    13:00 68.3 2.02 61.1 6.87 10.8 2.09 47.1 3.37

    13:15 68.2 1.23 60.5 5.54 13.5 1.54 47.1 3.73

    13:30 67.9 1.22 65.3 7.56 17.2 1.01 47 3.04

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    13:45 67.4 1.19 63.8 8.6 14.4 2.02 47 2.44

    14:00 67.6 1.08 64.4 4.29 10.5 4.29 47.1 1.08

    14:15 67.5 0.89 60.4 2.09 13.1 2.09 47 2.81

    14:30 67.7 1.48 65.2 1.54 13.8 1.54 47.1 3.2214:45 67.9 1.41 65 1.01 17.9 1.01 47.2 3.85

    15:00 68.3 3.45 46.6 2.02 18.5 2.02 47.1 3.81

    15:15 67.8 9.82 62.2 1.23 17.6 1.23 47.1 3.22

    15:30 68.2 9.13 65 1.22 16.9 1.22 47.1 3.56

    15:45 68.3 7.14 63.6 1.19 17.7 1.19 46.9 3.04

    16:00 67.9 6.87 65.8 1.08 16 1.08 46.9 8.71

    16:15 68.1 4.29 65.2 0.89 18.5 0.89 46.9 9.81

    16:30 68 2.09 64 4.29 18.2 4.29 47.1 3.49

    16:45 68 4.29 63.6 2.09 19.7 2.09 47 3.01

    17:00 68.3 2.09 61.6 3.22 17 1.54 47.2 3.52

    17:15 68.1 1.54 65 3.8