San Francisco DTA Model:
Working Model Calibration
Part 1: Process
Greg Erhardt
Dan Tischler
Neema Nassir
SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY
DTA Peer Review Panel Meeting
July 25th, 2012
Agenda
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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
SAN FRANCISCO COUNTY TRANSPORTATION
Outline
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Model Overview
Calibration Approach
Speed Flow Parameters
• Presented by Dan Tischler & Neema Nassir
Model Calibration Runs
Current Model Parameters
Key Findings
3
Model Overview
Model Overview
• Natural
breakpoint at San
Bruno Mountain
Park
• 976 TAZs
• 22 external
stations
• 1,115 signals
• 3,726 stop
controlled
intersections
5
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
6
Calibration Approach
Calibration Approach
1.
2.
3.
4.
5.
Ensure quality inputs
Measure anything that can be measured
Evaluate the results qualitatively
Evaluate the results quantitatively
Make defensible adjustments
8
• Identify and investigate
failed signal imports
• Spot check stopcontrol—some issues
with direction of 2-way
stops
• Automate as much as
possible
DESCRIPTION: New cycle lengths, made part of SOMA system
CHANGE
Intersection No.
ENGINEER:
NOTES:
32
24313000
R.Olea
PHASE STREET NAME FLASH Controller:
2070
2,6
Mission
R
Cabinet
M-SF
8
09th St
R
Operation Date: 2/29/1956
Soma (TBC)
System:
5th/How ard
Master:
Cascade:
PN/JD
10:20
Electrician
Time:
Date:
03/01/2006
X = YES
6:00
15:00
OPERATION TIMES
PLAN ONE (1)
M T W T F S CYCLE
-- = NO S
to
to
10:00
18:30
ALL OTHER TIMES
STREET
PHASE
X
X
X
X
X
X
X
X
---
2
3
1
1
2
3
---
X
X
X
X
X
X
X
1
1
1
--
1
2
3
4
5
6
7
8
Y
R
G
Y
R
Mission St WB
6
G
Y
R
09th St NB
8
R
G
Peds Xing 09th St SS
2P
W FRH
RH
Peds Xing 09th St NS
6P
W FRH
RH
Peds Xing Mission WS
4P
RH
W FRH
RH
Peds Xing Mission ES
8P
RH
W FRH
RH
60.0
60.0
60.0
20
20
20
1
2
3
4
9
10 11 12 13 14 15
SIGNAL INTERVALS (seconds)
5
6
7
8
9
10 11
12
13
14
15
CHANGE
111
212
313
FLASH
X
X
2
CYCLE OFFSET
(seconds) (seconds)
OFFSET
---
Mission St EB
CSO
SPLIT
09th St and Mission St
Ensure Quality
Inputs
09th St and Mission St
12.0 12.0 3.5 0.5 18.0 10.0 3.5 0.5
12.0 12.0 3.5 0.5 18.0 10.0 3.5 0.5
12.0 12.0 3.5 0.5 18.0 10.0 3.5 0.5
32
9
Measure Anything that can be
Measured
• Measure speed
flow parameters
• Change perceived
cost instead of
measured speed
and capacity
• Avoid arbitrary
demand changes
10
Evaluate Qualitatively
Example of extreme congestion
11
Evaluate Quantitatively
• Relative gap,
RMSE, GEH, RSquared
• Scatter plots,
maps
• Tables by: area
type, facility type,
speed, turn type,
time period, etc.
• Corridor plots
• Speeds
12
Make Defensible Adjustments
• Evaluate results and investigate worse offenders
• Hypothesize problems and propose changes
20 Worst Links with Volumes too Low
LinkID Label
15034 HARRISON ST
13221 SUNSET BLVD
13221 SUNSET BLVD
13223 SUNSET BLVD
32848 HARRISON ST
28691 GEARY BLVD
9010899 HARRISON ST
15034 HARRISON ST
28691 GEARY BLVD
16027 HARRISON ST
FacilityType FreeflowSpeed NumLanes StartTime EndTime CountVolume ModelVolume Diff
4
30
5 17:00:00 18:00:00
2093
368
4
35
3 17:00:00 18:00:00
2514
884
4
35
3 16:00:00 17:00:00
2248
961
4
35
3 17:00:00 18:00:00
2204
926
4
30
5 17:00:00 18:00:00
1443
186
6
30
1 17:00:00 18:00:00
1300
47
4
30
5 17:00:00 18:00:00
1946
722
4
30
5 16:00:00 17:00:00
1664
461
6
30
1 16:00:00 17:00:00
1264
67
4
30
5 17:00:00 18:00:00
1900
737
-1725
-1630
-1287
-1278
-1257
-1253
-1224
-1203
-1197
-1163
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Speed Flow Parameters
Model Calibration Runs
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
16
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
Free Flow Speeds
Free Flow Speed
(mph)
Local
Collector
Minor Arterial
Major Arterial
Super Arterial
Fwy-Fwy Connect
Expressway
Freeway
Regional
Core
25
25
30
30
30
35
60
CBD
25
25
30
30
30
40
65
Urban Biz
30
30
35
35
35
45
65
Urban
30
30
35
35
35
45
65
60
65
65
65
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Response Time Factors
Response Time
Factor*
Local
Collector
Minor Arterial
Major Arterial
Super Arterial
Fwy-Fwy Connect
Expressway
Freeway
Regional
Core
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.1
CBD
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.1
Urban Biz
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.1
Urban
1.2
1.2
1.2
1.2
1.2
1.2
1.2
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)
Local
Collector
Minor Arterial
Major Arterial
Super Arterial
Fwy-Fwy Connect
Expressway
Freeway
Regional
Core
1671
1671
1760
1760
1760
1830
2031
2185
CBD
1671
1671
1760
1760
1760
1886
2055
2213
Urban Biz
1760
1760
1830
1830
1830
1932
2055
2213
Urban
1760
1760
1830
1830
1830
1932
2055
2213
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Other Traffic Flow Parameters
Effective Length (Ft.)
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Effective Length Factor
1.17
Jam 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:
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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:
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•
•
•
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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
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?