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Modelling Experience - Coggle Diagram
Modelling Experience
Experience
Thesis - Modelling the South East Busway in Traffic
Microsimulation Software AIMSUN”
- Goal: Test infrastructure improvements and operational changes to improve capacity of the busway. Test the capability of Aimsun and Legion for this task, an unknown to the study team. Roughly 20000 pax per hr demand/capacity.
- Initially wanted to see how changing station layout affected station capacity, bus dwell times, bus route travel times e.g. KGS vs Cultrual centre layout, where peds know where to lineup vs where buses pull in where available space
- Testing changed pedestrian boarding/alighting points, moving go-card payments to station rather than tap on the bus
- test bus route operations e.g. express, SEB extensions, bus station geometric changes e.g. extensions at bottle necks
- Network constructed - initial import from openstreetmap, develoing busway station based on layout map from TransLink website, PT line input, intersections,
- Bus routes manually input
- Go card data used to model peak-hour volume - collaboration with Masters student
- Functioning model built
- At the time, Aimsun did not have capability to dynamically model pedestrian-bus interaction as a function of the bus station layout, affected scope of project. Found out late in project about out Legion licensing limit of maximum 1000 peds, end of project.
- Skills learned:
- building the network in Aimsun/Legion - cleaning/updating OSM network export layers, road infrastructure, PT /stop station layouts, veh/pax ODs, defining vehicles, defining OD paths at stations (multi exits, entries for big stations), busway intersections + signal phasing + actuators
- learning to input demand data
- creating visualisations in Aimsun/Legion - view styles of DOS, delay, avg speed, queue etc
- testing and modifying pedestrian parameters and infrastructure - visuals, size, O/Ds, decision nodes and walk paths to steer between O/Ds, obstacles, level change objects, grade seperation crossings, interaction with PT - PT stops, lines, OD matrices,d well time defined as time distribution and time per passenger, setting up model simulations - scenarios, Demand matrices, PT plans, control plans, output collection, route choice type
Sidra
- Big corridors
- Phasing testing
- Ped protection phases, shared phases
- networking
- Bus priority/ vehicle definition
- Network sidra models for complicated intersections e.g. the Ramp metered RA
Meso
- Intersection phasing updates based on ICA data - get average cycle times, averaging over many days
- Model network updating
- Extracting network IDs for use in database output manipulation - spreadsheet analysis
- Grouping roads / intersections / roundabouts
- Update LOS paramters in models
Micro
- Model Network building - current and future project updates network codiing, calbrated using real network data
- Different types of traffic assignment - STA, DTA, Dynamic User Equilibrium
- Model convergence - checking traffic assignment reuslts are acceptable using multiple Stochastic Route Choice SRC assignment then using average to evaluate model calibration
- OD data usually gotten from strategic or meso model depending on study area isze
- Traffic survey gathering - to set up calibration/validation traffic data - vehicle classification, get to match model data format e.g. 15m intervals in Real Data Set file format, queuing data
- PT fleet and schedules - TEARC, Busway, using detectors on raillines to actuate signals
- Scenario management / processing - settings, seed#
- Interval length adjustment and calculations
- Calibration - reviewing simulated flows against survey/ OD count data - creating route objects etc to count movements - querying database output
- Calibration measures include GEH (<5 for 95% links) statistics (actual difference), scatter plot (R2 value>0.9 for all observations) and root mean square error (RMSE <30% all observations)) (relative difference and goodness of fit).
- Calibrate strategic model OD data against coutn data using the ‘Static OD Adjustment’ tool of Aimsun
- Validation usually done with screen lines or travel times (e.g. define a sub-path and observe model time)
- Calibrate by changing model parameters - section acceleration, sat flow, gap acceptance etc, forced lane utilization etc - apply splits
- Averaging simulation runs in spreadsheets
- Applying network simulations view modese.g. LOS, flow, queue lengths and producing outputs for reporting - defining the attributes to be presented
- Reporting future case results - comparing options using network statistics such as average speed and density on network, total delay and travel time
Spreadsheet analysis
- Volume network diagrams for background + future options (growth + changed network)
- Model calibration/validation - VLOOKUP for network id + volumes to match survey volumes - double check this
- Model output statistics - VLOOKUP on database outputs for networks statistics for different options for reporting
- Extracting data outputs via mySQL - obtain section IDs, extract section table from SQL database, get network statistics
- Used to obtain peak hr only results etc
- Travel time and flow comparisons
- Demand adjustment (OD matrix) - black box to me e.g. delta matrix