Development of a Flexible Zoning System Applied to National or State-wide Models
Dr. Henry Le, AECOM, Craig Somerville, Department of Transport, Planning and Local Infrastructure Victoria, Dr. Oliver Charlesworth, Citilabs
A methodology for a flexible zone system to allow a very large network model to be compressed easily so that a transport model can focus on a study area with detailed zones while the surrounding zones are aggregated for acceptable run times.
The state of Victoria, Australia, requires nearly 7,000 transport zones in their State-wide Victoria Integrated Transport Model (SVITM) to represent the detailed travel over approximately 227 thousand square kilometres. Local councils and other government planning authorities wish to study in detail the impact of growth on regional transport networks whilst maintaining consistency in the measurement of network performance and cost benefit analysis for proposed transport improvements. To have one model covering all regional areas ensures consistency and fairness for the investment of transport infrastructure across the state.
Such a large number of zones however would have adverse impacts on model run time. A full model run with a 7,000 zone network would take 7 days to complete which is not acceptable for calibration and application of the model. A flexible zone system derived by the Victorian Department of Transport, Planning and Local Infrastructure (DTPLI) and AECOM is presented and discussed here which allows a zone system and associated network to be compressed easily. A transport model can then focus on a study area with detailed zones while the surrounding zones are aggregated to a level that allows model run times to be within an acceptable range, i.e. within 24 hours.
In one example of this flexible zoning application, the model was compressed to 1,370 zones which included 700 zones for the study area, 500 zones for Melbourne area, and 170 zones for the remaining area. The model run time for this 1,370 zone system was reduced from 7 days to ½ a day.
It is this innovation, the flexible zone system in the SVITM, which won the authors of this work the AITPM Excellence Awards 2014 in the category of Transport and Land Use Modelling.
Association for European Transport