Calculation models
The calculation models form the predictive engine of Urban Strategy. They provide quantifiable insights into the impacts and trade-offs of policy interventions, enabling data-driven decisions to improve liveability, accessibility, and sustainability.
How the models work
Each model calculates on a Graphic Processing Unit (GPU). Unlike a Central Processing Unit (CPU) that handles tasks sequentially using a few cores, a GPU uses thousands of smaller cores to perform many calculations in parallel. By implementing the algorithms to run on GPU's, the calculation times of the models are maximally reduced without compromising on quality or detail. This enables to interactively run the large and complex calculatios on a city scale.
Each calculation model runs independently. Therefore multiple models can run in parallel even if the output from one model forms the input for anotherone. Models only (re)calculates upon a datachange in the data collection the model is subscribed to. As data flows asynchronously, the source of the datachange is irellevant. It can be a manual change by the user, an overwrite by a control in the Webinterface, sensor data or output from one of the other calculation models.
Quickstart guide
This quickstart guide assumes you have access to a configured Urban Strategy project with an approved account and knowledge of how to operate the Portal, the Webinterface and how to create scenarios.
Start using a calculation model in your scenario by:
- Login to the portal and open your project .
- Verify the active scenario, the model reads from and writes to the active scenario only.
- Open the modules panel in the top right corner of the Webinterface.
- Start the model by selecting the icon. After a few seconds the model state will change from busy to ready, indicating results of scenario are published.
- You can now create, activate or change controls in the active scenario, the model will respond automatically.
- To stop the model, click on the icon.
Model overview
Four-step transportation model
| Calculation model | Description |
|---|---|
| Trip generation | Generates the number of trips produced by and attracted to each zone based on features such as housing, stores and offices in that zone, and feature-specific demand generation factors per purpose and population group. |
| Mode & destination choice | Calculates mode and destination choice by modelling traveller preferences based on trip productions, attractions, accessibility, and population characteristics using multinomial logit utility functions. |
| Traffic assignment | Calculates the route choice for all road-bound trips through the road network, using Dijkstra algorithm to find each trip's shortest path and iterating toward an equilibrium through deterministic multi-user-class assignment. |
| Public transit | Calculates the route choice for all transit-bound trips through the public transit network, combining Dijkstra and Eppstein algorithms to spread demand realistically across multiple paths. |
Demand matrix tools
| Calculation model | Description |
|---|---|
| Matrix Estimator | Fine-tunes the travel demand matrix to match real traffic counts based on an iterative traffic assignment runs. |
| Matrix Manipulator | Allows for operations on the travel demand matrix based on controls, such as rerouting trips through a hub and shifting/scaling trips between matrices. |
Environmental impact
| Calculation model | Description |
|---|---|
| Air | Calculates the air pollutants, such as NO2, PM10, and CO2, from traffic emissions, urban form and meterology, using the SRM1 and SRM2 calculation methods. |
| Noise Traffic | Calculates noise levels (Lden) from traffic sources using the SRM2 calculation method |
| Noise Industry | Calculates noise levels (Lden) from industrial sources using the SRM2 calculation method |
| Receptors | Generates grid, road, building and screen receptors. |
| Indicator buildings | Turns the air quality and noise levels reaching a building's facade into an exposure map, making it easy to identify buildings above a chosen thresholds. |
Visualization & publishing
| Calculation model | Description |
|---|---|
| Publisher | Provides the interaction between a frontend service and the IMB Hub by publishing 2D map layers. |
| Publisher3D | Provides the interaction between a frontend service and the IMB Hub by publishing 3D map layers. |
| PublishedTilers | Provides the interaction between a frontend service and the IMB Hub by publishing XYZ tiles. |
| Tiler | Renders the map layers provided by the Publisher. |
| Indicators | Turns indicator definitions into graphs and charts in the Webinterface results panel. |
| TransitLines | Generates a visual offset between transitlines to easily select a single transit line in the Webinterface. |