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SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY
San Francisco DTA Model: Working Model Calibration
Part 1: Process
Greg ErhardtDan Tischler
Neema Nassir
DTA Peer Review Panel MeetingJuly 25th, 2012
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SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY
Agenda
• 9:00 Background• 9:30 Technical Overview – Part 1
• Development Process and Code Base/Network Development
• 10:15 Break• 10:30 Technical Overview – Part 2
• Calibration and Integration Strategies
• 12:00 Working Lunch / Discussion• 2:00 Panel Caucus (closed)• 3:30 Panel report• 5:30 Adjourn
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Outline
• Model Overview• Calibration Approach• Speed Flow Parameters
• Presented by Dan Tischler & Neema Nassir
• Model Calibration Runs• Current Model Parameters• Key Findings
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Model Overview
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Model Overview
• Natural breakpoint at San Bruno Mountain Park• 976 TAZs• 22 external stations• 1,115 signals• 3,726 stop controlled intersections
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Model Overview
• PM Peak Model from 4:30-6:30 pm• 1 hour warm-up time• 3 hour network clearing time• 270,000 internal trips• 180,000 IX , XI or XX trips Dynameq Software
Platform
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Calibration Approach
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Calibration Approach
1. Ensure quality inputs2. Measure anything that can be
measured3. Evaluate the results qualitatively4. Evaluate the results quantitatively5. Make defensible adjustments
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Ensure Quality Inputs• Identify and investigate failed signal imports• Spot check stop-control—some issues with direction of 2-way stops• Automate as much as possible
DESCRIPTION:
NOTES:
S M T W T F S
to -- X X X X X --to -- X X X X X --
X X X X X X X
PHASE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
2 G Y R
6 G Y R
8 R G Y R
2P W FRH RH
6P W FRH RH
4P RH W FRH RH
8P RH W FRH RH
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
12.0 12.0 3.5 0.5 18.0 10.0 3.5 0.512.0 12.0 3.5 0.5 18.0 10.0 3.5 0.512.0 12.0 3.5 0.5 18.0 10.0 3.5 0.5
X = YES -- = NO
Mission St EB
ALL OTHER TIMES
18:30
CYCLE
212313
(seconds)
STREET
Mission St WB
Peds Xing 09th St SS
Peds Xing 09th St NS
09th St and Mission St
CH
AN
GE
60.0
10:00
60.0
Peds Xing Mission WS
09th St NB
OFFSET(seconds)
Peds Xing Mission ES
60.0
CSO
111
--1
1
6:0015:00
FLASHOFFSET
----
23
1
SPLIT 11
2
CYCLE
3
Controller:CabinetOperation Date:System:Master:Cascade:
2070M-SF
2/29/19562,6
STREET NAMEMission09th St8
Soma (TBC)5th/How ard
FLASHRR
09th St and Mission St
32
New cycle lengths, made part of SOMA system
24313000
10:2003/01/2006
PHASE
PN/JD
32
CHANGEIntersection No.ENGINEER:
Electrician
SIGNAL INTERVALS (seconds)
R.Olea
202020
OPERATION TIMESPLAN ONE (1)
Time:Date:
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Measure Anything that can be Measured• Measure speed flow parameters• Change perceived cost instead of measured speed and capacity• Avoid arbitrary demand changes
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Evaluate Qualitatively
Example of extreme congestion
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Evaluate Quantitatively
• Relative gap, RMSE, GEH, R-Squared• Scatter plots, maps• Tables by: area type, facility type, speed, turn type, time period, etc. • Corridor plots• Speeds
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Make Defensible Adjustments
• Evaluate results and investigate worse offenders• Hypothesize problems and propose changes20 Worst Links with Volumes too Low
LinkID Label FacilityType FreeflowSpeed NumLanes StartTime EndTime CountVolume ModelVolume Diff15034 HARRISON ST 4 30 5 17:00:00 18:00:00 2093 368 -172513221 SUNSET BLVD 4 35 3 17:00:00 18:00:00 2514 884 -163013221 SUNSET BLVD 4 35 3 16:00:00 17:00:00 2248 961 -128713223 SUNSET BLVD 4 35 3 17:00:00 18:00:00 2204 926 -127832848 HARRISON ST 4 30 5 17:00:00 18:00:00 1443 186 -125728691 GEARY BLVD 6 30 1 17:00:00 18:00:00 1300 47 -1253
9010899 HARRISON ST 4 30 5 17:00:00 18:00:00 1946 722 -122415034 HARRISON ST 4 30 5 16:00:00 17:00:00 1664 461 -120328691 GEARY BLVD 6 30 1 16:00:00 17:00:00 1264 67 -119716027 HARRISON ST 4 30 5 17:00:00 18:00:00 1900 737 -1163
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Speed Flow Parameters
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Model Calibration Runs
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Base Case – July 6 Test
Change(s):
Results:
• RMSE: Links = 133 (58%), Movements = 64 (80%)
• GEH: Links = 7.17, Movements = 4.59
• Overall Vol/Count Ratio: Links = 0.6527, Movements = 0.7145
• This test includes intrazonal trips (assigned to the nearest centroid) and ambiguous two-way stop signs re-assigned as all-way stops
• At this stage, there were still network and signal issues that have since been dealt with
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Test 1 – Speed-Flow Curve Changes
Change(s): Free-flow speed, response time factor, effective length factor
Results:
• RMSE: Links = 132 (57%), Movements = 64 (80%)
• GEH: Links = 7.04, Movements = 4.56
• Overall Vol/Count Ratio: Links = 0.6467, Movements = 0.7051
• Increasing RTF and decreasing speeds caused gridlock in the CBD
• Without bus-only lanes, these changes have more impact
• With bus-only lanes included, capacities are too low and CBD is full of gridlock
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Test 2 – Removing Bus-only Lanes:Stockton Street Example
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Test 2 – Removing Bus-only Lanes
Change(s): Bus-only lanes no longer specified as bus-only
Results:
• RMSE: Links = 135 (59%), Movements = 64 (80%)
• GEH: Links = 7.32, Movements = 4.59
• Overall Vol/Count Ratio: Links = 0.6459, Movements = 0.7085
• Got rid of gridlock in CBD
• People are allowed to use these lanes for right turns – how can we model that?
• Need to add them back in some way while still allowing for limited use – next test.
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Test 3 – Increasing Demand
Change(s): Increasing internal demand by 30%
Results:
• RMSE: Links = 155 (68%), Movements = 72 (90%)
• GEH: Links = 8.18, Movements = 4.86
• Overall Vol/Count Ratio: Links = 0.6316, Movements = 0.7526
• Significant gridlock all over the network
• Previously about 30% low on counts, but more demand overloads the network
• Need to fix flow patterns and speeds, not demand
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Test 4 – Penalizing Locals & Collectors
DTA Volumes Static Volumes
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Test 4 – Penalizing Locals & Collectors
DTA Volumes Static Volumes
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Test 4 – Penalizing Locals & Collectors
Change(s): Local and collector links had penalty of 1*FFTime added to generalized cost
Results:
• RMSE: Links = 122 (53%), Movements = 61 (76%)
• GEH: Links = 6.85, Movements = 4.47
• Overall Vol/Count Ratio: Links = 0.8074, Movements = 0.855
• Arterial Plus flows are still much lower than expected – looking at speed-flow curves
• Important to test this again with transit-only lanes added back in some way
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Current Model Parameters
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Free Flow Speeds
Free Flow Speed (mph)
Regional Core CBD Urban Biz Urban
Local 25 25 30 30Collector 25 25 30 30Minor Arterial 30 30 35 35Major Arterial 30 30 35 35Super Arterial 30 30 35 35Fwy-Fwy Connect 35 40 45 45Expressway 60 65 65 65Freeway 60 65 65 65
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Response Time Factors
Response Time Factor*
Regional Core CBD Urban Biz Urban
Local 1.2 1.2 1.2 1.2Collector 1.2 1.2 1.2 1.2Minor Arterial 1.2 1.2 1.2 1.2Major Arterial 1.2 1.2 1.2 1.2Super Arterial 1.2 1.2 1.2 1.2Fwy-Fwy Connect 1.2 1.2 1.2 1.2Expressway 1.2 1.2 1.2 1.2Freeway 1.1 1.1 1.1 1.1
* Response times corresponding to RTF equal to 1.1 and 1.2 are respectively 1.375 and 1.5 seconds
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Saturation Flow Rates
Saturation Flow (vphpl)
Regional Core CBD Urban Biz Urban
Local 1671 1671 1760 1760Collector 1671 1671 1760 1760Minor Arterial 1760 1760 1830 1830Major Arterial 1760 1760 1830 1830Super Arterial 1760 1760 1830 1830Fwy-Fwy Connect 1830 1886 1932 1932Expressway 2031 2055 2055 2055Freeway 2185 2213 2213 2213
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Other Traffic Flow Parameters
Effective Length (Ft.) 24Effective Length Factor 1.17Jam density (vpmpl) 220
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Assignment Specification
These values define the period of the simulation: • Start of demand: 15:30 • End of demand: 18:30 • End of simulation period: 21:30 • Transit lines simulation: Yes • Re-optimization: No • Re-optimization iteration(s): 0
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Demand Specification
Demand and generalized cost for cars: • class: Car_NoToll • matrix: car_notoll • paths: 20 • intervals: 12 • types (%): Car=100, • generalized cost: movement expression + link expression• movement expression: ptime+(left_turn_pc*left_turn)+
(right_turn_pc*right_turn) • link expression: fac_type_pen*(3600*length/fspeed)
Demand and generalized cost for trucks: • class: Truck_NoToll • matrix: truck_notoll • paths: 20 • intervals: 12 • types (%): Truck=100, • generalized cost: movement expression + link expression movement
expression: ptime+(left_turn_pc*left_turn)+(right_turn_pc*right_turn) • link expression: fac_type_pen*(3600*length/fspeed)
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Control Plans and Results Specifications
Signals are applied during this period: • excelSignalsToDynameq: 15:30 - 18:30
These settings specify the time steps used by Dynameq. The purpose of these settings is just for analysis of the DTA results and doesn’t have any bearing on the results themselves.
• Simulation results: 15:30:00 - 21:30:00 -- 00:05:00
• Lane queue animation: 15:30:00 - 21:30:00 -- 00:05:00
• Transit results: 15:30:00 - 21:30:00 -- 00:05:00
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Advanced Specifications
These values are settings for the DTA method used by Dynameq.
• Traffic generator: Conditional • Random seed: 1 • Travel times averaged over: 450 s • Path pruning: 0.001 • MSA reset: 3 • Dynamic path search: No • MSA method: Flow Balancing • Effective length factor: 1.00 • Response time factor: 1.00
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Key Findings
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Key Findings
• Model is sensitive to changes, and can easily regress into gridlock.
• Bus-only lanes matter.• Penalizing locals and collectors helps. • Increasing internal demand 10% helps.
Increasing demand 30% causes gridlock. • Most runs show less congestion than we
would anticipate.
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Questions?