Traffic Simulation L3b – Steps in designing a model Ing. Ondřej Přibyl, Ph.D.

L3: Steps in designing a model Course: Traffic Simulation 2 Major steps in simulation 2. Data collection 1. Conceptual model 3. Base model development 4. Error checking Compare model to field data Acceptable match? 6. Alternatiní analyses 7. Final report 5. Adjust model’s parameters NoNo Working Model before calibration Calibrated Model Yes Work prior to actual modeling Initial modeling Calibration Model Application

L3: Steps in designing a model Course: Traffic Simulation 3 1. Conceptual model   Determine Goals and Objectives  What do you what to do with the model  It may be an end in itself  More often, it is a means to an end  Goals may not be known when you start the project!  One often learns things along the way  Prepare conceptual model  An abstract representation of the system  What should be included in model? What can be left out?  What abstractions should be used? What is the level of details?  Which type of model will be used (micro/macro simulation, …)

L3: Steps in designing a model Course: Traffic Simulation 4 1. Define Project Milestones 1. Study Scope 2. Data Collection Report 3. Model 50% coded files 4. Model 100% coded files. 5. Calibration Report 6. Alternatives Analysis report. 7. Final Report

L3: Steps in designing a model Course: Traffic Simulation 5 2. Data Collection and Preparation   Geometry (lanes, lengths, intersects)   Control (signal timing)   Demand (turn moves or OD)   Calibration Data  Volumes, capacities, travel times

L3: Steps in designing a model Course: Traffic Simulation 6 Major steps in simulation 2. Data collection 1. Conceptual model 3. Base model development 4. Error checking Compare model to field data Acceptable match? 6. Alternatiní analyses 7. Final report 5. Adjust model’s parameters NoNo Working Model before calibration Calibrated Model Yes Work prior to actual modeling Initial modeling Calibration Model Aplication

L3: Steps in designing a model Course: Traffic Simulation 7 3. Code base model 1. Link-Node Diagram 2. Code links 3. Code control data 4. Code demand data 5. Code simulation control data

L3: Steps in designing a model Course: Traffic Simulation 8 4. Error Checking To detect the major errors (not connected links, traffic clearly out of normal, …) 1. Check web for known software errors 2. Review inputs 3. Review animation Single vehicle, low volumes, full volume

L3: Steps in designing a model Course: Traffic Simulation 9 Major steps in simulation 2. Data collection 1. Conceptual model 3. Base model development 4. Error checking Compare model to field data Acceptable match? 6. Alternatiní analyses 7. Final report 5. Adjust model’s parameters NoNo Working Model before calibration Calibrated Model Yes Work prior to actual modeling Initial modeling Calibration Model Aplication

L3: Steps in designing a model Course: Traffic Simulation Calibration Calibration to capacity Identify calibration parameters and sites Global calibration Fine tune link capacities Route choice calibration Identify calibration parameters and sites Global calibration Fine tune link

L3: Steps in designing a model Course: Traffic Simulation Calibration (2) System Performance Calibration Identify calibration parameters and sites Global calibration Fine tune link TRB Paper (Session 262) Guidelines for Calibration of Microsimulation Models: Framework and Applications

L3: Steps in designing a model Course: Traffic Simulation 12 Major steps in simulation 2. Data collection 1. Conceptual model 3. Base model development 4. Error checking Compare model to field data Acceptable match? 6. Alternatiní analyses 7. Final report 5. Adjust model’s parameters NoNo Working Model before calibration Calibrated Model Yes Work prior to actual modeling Initial modeling Calibration Model Aplication

L3: Steps in designing a model Course: Traffic Simulation Alternatives Analysis Our objective is not just to see how the situation is, however how it will/would be It should answer questions such as: How will the situation look like in future? - Annual increase in traffic - Building of new infrastructure (roads, shopping centers, …) Which of proposed alternatives is the best? - one lane or two lanes? - roundabout or signalized intersection? Determination of LOS Comparison to other engineering methods (capacity analysis)

L3: Steps in designing a model Course: Traffic Simulation 14 Task 7. Documentation Study Objectives and Scope Study Approach (tools, rationale) Data Collection Calibration Tests and Results Baseline Forecast Assumptions Description of Alternatives Results

Additional issues

L3: Steps in designing a model Course: Traffic Simulation 16 Run of the model 1. Initialisation of the system (warming up) - to fill in the network with vehicles - to get stabilized run 2. Simulation run The simulation must be repeated several times with different random number seeds (depends on the random number generator)

L3: Steps in designing a model Course: Traffic Simulation 17 Discussion How many runs do we need?

L3: Steps in designing a model Course: Traffic Simulation 18 Normální rozdělení – doba jízdy

L3: Steps in designing a model Course: Traffic Simulation 19 How many runs do we need? It is a random process std - standard deviation from the collected sample d – requested precision α – significance level - critical value for a normal distribution Example: α = 0.05 (5%) d = 0.01 (1%) std = 0.15 = 1.96 n = 5.46 ~ 6

Thank you for your attention Questions?