Simulation-Based Equilibrium Assignment: Insights and Future Challenges Michael Mahut, Michael Florian and Nicolas Tremblay INRO Montreal, Canada 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Agenda Overview of DTA Bakersfield Project Calibration approach Advances in assignment methodology Conclusions 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Types of DTA models microsimulation microsimulation high fidelity car following gap acceptance lane changing high fidelity fluid / CTM low fidelity volume-delay & constraints one-pass iterative 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Equilibrium DTA 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Agenda Overview of DTA Bakersfield Project Calibration approach Advances in assignment methodology Conclusions 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Network 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Calibration Data Data provided Other potential data 2005 turning movement counts (16 major intersections) 2005 Route 99 car and truck counts 2006 AM & PM qualitative queuing observations Other potential data speed measurements travel time probes Counts from Kern COG – AM and PM 15-minute movement counts for cars only on arterials Caltrans District 6 collected car&truck link flows on ramps and 1 freeway count cars only when counts taken? single visual queuing observations AM and PM 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Network 1 mile 1 km 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Link Flows 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Relative Gaps This is a typical convergence plot (1 graph for each departure interval): Stabilizes naturally at a certain value of rel-gap Avg at 70 iterations is 5.0%: quite typical NOTE: good convergence does not necessarily mean good results! you would not say that a static model is superior to a dynamic model because it gets better convergence: lower convergence is a necessary result of the higher level of reality in the model; this also holds true also for the various types of DTA: the ones with more approximate representation of traffic would be expected to get better convergence! The real question is: how good are the results?? 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Calibration Results predicted flows counts interval slope R2 4:15-4:30 1.05 91% 4:30-4:45 1.01 89% 4:45-5:00 1.03 89% 5:00-5:15 0.94 88% 5:15-5:30 0.89 86% 5:30-5:45 1.04 86% interval slope R2 7:15-7:30 0.96 93% 7:30-7:45 0.91 89% 7:45-8:00 0.91 88% 8:00-8:15 1.07 91% 8:15-8:30 1.09 91% 8:30-8:45 1.17 89% predicted flows skip first & last intervals counts often show variability Dynameq results have little variability counts 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Queues 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Performance Demand Trips RAM CPU  Speed-up 4x30-minute matrices, 2 classes Trips 61000 (car) + 2900 (truck) RAM 80 MB CPU  Speed-up per iteration: 66 sec  110x full DTA: 77 min  1.6x Partitions and zone groups Zone groups Simplify the use of zonal data Used for zone subset specification Used for submatrix specification 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Agenda Overview of DTA Bakersfield Project Calibration approach Advances in assignment methodology Conclusions 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Link Flows 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Select Link 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Path Flows 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Agenda Overview of DTA Bakersfield Project Calibration approach Advances in assignment methodology Conclusions 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

MSA Improvements general observation (1) dynamic reset MSA can be slow in removing flow from unattractive paths (1) dynamic reset Step-size increases with increasing departure interval (2) quasi-gradient Path-flow adjustment by O-D based on quasi-gradient Step size applied to total displaced flow (O-D) MSA can be very slow in removing flow from paths – can be a problem is unattractive paths are identified in the early iterations. Two improvements: Dynameq step-size adjustment Hybrid quasi-gradient / MSA approach 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

MSA 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Gradient + Reset 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Agenda Overview of DTA Bakersfield Project Calibration methodology Advances in methodology Conclusions 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

Conclusions Micro-simulation based DTA (Dynameq) Calibration can be applied to medium-sized networks and calibrated with reasonable effort Calibration demand side (path and O-D) causes: quickly identified using Select Link and Path Analysis tools Consistency (“Reproduce-ability”) Changes to demand or supply lead to reasonable (commensurate) changes to model outputs Equilibrium property is critical! 11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida

11th TRB Planning Applications Conference May 6-9, 2007. Daytona Beach, Florida