Calibration Approach

Calibration objectives

In calibrating the model to accurately represent traffic conditions in the corridor, the AMS team's objectives are:

  • Simulation of representative traffic volumes on the freeway and arterials for the time period considered
  • Replication of bottlenecks on the freeway (location, speed, extent)
  • Replication of observed queuing at intersections (observed approach speeds, location of queues, queue extent)

Calibration tiers

The AMS team is taking a tiered approach to calibration:

Detailed calibration of freeways
  • Flows and speeds on mainline/HOV sections
  • Major bottlenecks
  • Ramp queues
Reasonable calibration of key network arterials
  • Flows and speeds on arterial segments
  • Turning proportions at key intersections
  • Queues at key intersections
Rough calibration of arterials at edge of network
  • Observed flows 
  • No unusual congestion at main intersections

Calibration steps

Overall steps in the calibration process are:

  1. Recreate congestion using constant average demand for the simulation period.
  2. Adjust OD matrices based on observed data.
  3. Recreate congestion using demand profile(s) for each simulation period.

The process is applied in this way:

Preliminary calibration using a small area
  • Saves time by allowing quicker simulation than full network
  • Global parameters
  • Template for freeway merge/diverge areas
  • Template for congested intersections
Full network calibration based on results of the small calibration effort
  • Minor adjustment of global parameters / templates
  • Calibration of local congestion hotspots

Further information on calibrating the model, including calibration guidelines, detailed steps, and examples, can be found in the AMS Phase 2 presentation.