To meaningfully predict what traffic might look like under different response scenarios, it is essential to have a representation of current traffic conditions in the corridor that can be used as a starting point for a simulation.
Freeway estimation
Real-time data exist at specific points along the freeway, but some gaps remain. Estimation fills in the blanks to provide a complete picture of traffic state:
The basic dimensions of freeway traffic estimation are:
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The estimation process looks like this:
The network description, fundamental diagrams, boundary flows, and turning movements are input into a CTM-based model and then assimilated with real-time detector data to generate the estimated freeway traffic state. (In AMS Phase 2, CTM is used for freeway estimation only, not for simulation.)
Arterial estimation
For arterial traffic estimation, the basic dimensions are:
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Further details on the estimation process and calibration of the freeway and arterial estimators can be found in the AMS Phase 2 presentation.