1. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY DTA Anyway Peer Review Panel Traffic Flow Model Parameters Estimation July 25 th, 2012

2. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY2 Problem Statement Do … default traffic flow settings reflect local conditions? traffic flow parameter differences between facility and area classifications accurately reflect differences? the slopes of San Francisco’s famously hilly streets affect traffic flow conditions (in a meaningful way)? Source: SF Citizen - http://sfcitizen.com/blog/tag/cable-cars/

3. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY3 Dynameq Representation of Traffic Flow Triangular fundamental diagram Flow (q) Density (k) Critical Density (kc) Saturation Flow Rate 1 FFS 1

4. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY4 Dynameq Representation of Traffic Flow Parameters Free-flow speed (FFS) - mph Saturation flow rate (Q s ) - pcuplph Inverse of saturation flow headway (H) - sec Response time (RT) - sec Backwards wave speed (BWS) - mph Jam density (K j ) - pcuplpm Inverse of effective car length (EL) - ft

5. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY5 Challenges: Triangular simplification forces compromises Uninterrupted “flow-density”, “speed-flow”, or “speed-density” data is required (not available for all the network) Use FFS, H, EL, and RT instead Lack of data for RT and EL Relating “Real” Speed-Flow to Dynameq Parameters

6. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY6 Data Resources Existing resources Caltrans PeMS (for freeways) SFMTA speed surveys New resources Traffic flow observations

7. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY7 Caltrans Performance Measurement System (PeMS) Caltrans freeway sensors Real-time and time-series traffic flow data Counts, speeds, occupancy, etc. San Francisco coverage: 15 sensors US-101, I-280, and I-80 Resolution of 5-minute period, individual lanes Reference period - May 2012.

8. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY8 Caltrans Performance Measurement System (PeMS) San Francisco sensor locations

9. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY9 Caltrans Performance Measurement System (PeMS) Analysis Generated hourly flow-density scatter plot Piece-wise linear (triangular) curves were extracted from flow-density scatter plots for 59 freeway lanes in San Francisco Non- triangular trends were excluded 29 removed, 30 retained Used for estimation of: Free-flow speed Backwards wave speed Saturation flow rate

10. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY10 Caltrans Performance Measurement System (PeMS) Curve fitting for flow-density scatter plots Fixed points K j =220 Flow Density FFS BWS

11. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY11 Caltrans Performance Measurement System (PeMS) Curve fitting – triangular plot example 1 Flow vs. density scatter points, Highway 280, Lane 3 at Mission St.

12. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY12 Flow vs. density scatter points, Highway 280, Lane 3 at Alemany Blvd. Curve fitting – triangular plot example 2 Caltrans Performance Measurement System (PeMS)

13. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY13 Caltrans Performance Measurement System (PeMS) Flow vs. density scatter points, Highway 280, Lane 4 at Vermont St. Non-triangular density-flow plot example 1

14. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY14 Caltrans Performance Measurement System (PeMS) Flow vs. density scatter points, Highway 101, Lane 3 at 25 th St. Non-triangular density-flow plots example 2

15. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY15 San Francisco Municipal Transportation Agency (SFMTA) Speed Surveys Speed data collected for speed limit determination 500+ locations (~200 used for speed param. adjust) Observation facility types Arterial (most observations) Local/Collector (limited observations) Collection period from 2004 to 2012 Methodology 4 second headway requirement Off-peak hours during normal weather conditions 50 th and 85 th percentile speeds are used.

16. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY16 San Francisco Municipal Transportation Agency (SFMTA) Speed Surveys Speed survey locations Area Type AT=0 (reg’l core) 24 locs AT=1 (CBD)105 AT=2 (urban biz)164 AT=3 (urban)212 Facility Type Super arterial69 locs Major arterial187 Minor arterial134 Collector 56 Local57 Slope m < -8% 20 locs -8% < m < 8%467 m > 8%20

17. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY17 San Francisco Municipal Transportation Agency (SFMTA) Speed Surveys 50 th Percentile Speeds85 th Percentile Speeds AT \ FT (mph) Local / Collector Arterial Reg’l CoreNA26 CBD2526 Urban Biz2630 Urban2732 Suburban32NA AT \ FT (mph) Local / Collector Arterial Reg’l CoreNA30 CBD3031 Urban Biz3134 Urban3236 Suburban37NA

18. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY18 DTA Project Traffic Flow Survey Survey Design Objective Record saturation flow rate, backwards wave speed, and jam density on local, collector, and arterial streets of varying slope Methodology Observe jam density from queue spacing Observe backwards wave and saturation flow during queue release

19. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY19 DTA Project Traffic Flow Survey Time Saturation Flow RT EL Space Backward Shockwave H Red Light Queue Dissipation

20. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY20 DTA Project Traffic Flow Survey Collected data - vehicles Vehicle type (car, truck, bus, motorcycle) Queue positions Front bumper distance from stop bar Time when vehicle begins to move Time when vehicle passes stop bar Collected data - vehicles Approximate slope of street Lane width Movement permission by lane

21. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY21 DTA Project Traffic Flow Survey Ideal survey conditions Single vehicle type – passenger cars Consistently long queues (≥7 vehicles) Smooth queue dissipation – no downstream backup Absence of conflicts Turning movement pedestrian conflicts Lane changes

22. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY22 DTA Project Traffic Flow Survey Challenges Queue lengths Low facility type (local /collector) streets lack adequate volume Steep streets often lack heavy volumes Need flaw in signal progression for queue formation Congestion Promising locations suffer from congestion Conflicts Need multiple lanes in order to observe through- movement-only lanes

23. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY23 DTA Project Traffic Flow Survey Challenges (continued) Vehicles do not cooperate ! Tightening gaps after stopping What is the effective length? Inching forward at start of green phase before car in front accelerates What is the response time? Distracted drivers don’t notice the car in front is gone What is the headway?

24. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY24 DTA Project Traffic Flow Survey # Dir. Observ. Street Cross Street # of Lanes FT AT Measured Grade Network Grade # of Queues 1 NB Leavenworth O'Farrell3Minor ArtReg’l Core11.2%11.1%28 2 NB Leavenworth Geary3Minor ArtReg’l Core7.9%7.4%20 3 EB Golden Gate Franklin3Major ArtCBD Flat 42 4 EB O'Farrell Van Ness2Super ArtCBD-10%-10.3%42 5 NB Kearny Bush3Major ArtReg’l Core Flat 42 6 WB Fell Buchanan4Super ArtCBD5.2%9.7%42 7 SB Hyde Post3Minor ArtReg’l Core-7.9%-11.2%42 8 NB Taylor Post3CollectorReg’l Core8.5%8.3%20 9 NB Van Ness Golden Gate3Major ArtReg’l Core Flat 42 Survey Locations

25. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY25 DTA Project Traffic Flow Survey ParameterSlopeSample SizeMeanSt. Dev.Error (90%) Effective Length (Ft.) Down75624.545.410.32 Flat1,13424.055.140.25 Up99024.325.630.29 Headway (Sec.) Down7562.380.730.044 Flat1,1252.570.910.044 Up5582.720.780.054 Response Time (Sec.) Down7471.090.390.023 Flat3781.370.450.038 Up5581.380.900.062 Collected Data Summary Statistics

26. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY26 Parameter Data Sources Data sources for parameters by facility type Param. FT Free-flow SpeedSaturation FlowResponse TimeJam Density Freeway FTsPeMS Inferred from CBD arterials Arterial FTs SFMTA speed surveys CBD saturation headway observations CBD queue dissipation observations CBD arterial queue length observations Local & Collector FTs Limited SFMTA speed surveys & supplemental observations Mostly inferred from CBD arterials Red text = data limitations

27. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY27 Parameter Comparison Comparison of original / default parameters to updated parameters (no slope variation) Free-flow speeds increase in some ATs Response time is slower Jam density is lower Saturation flow rates are lower by 100-300 pcuplph Trade-off between saturation flow and response time Matching either param. to data throws other off Compromise is slightly high flow, slightly slow response

28. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY28 Parameter Comparison Freeway Area TypeSettings Free Flow Speed (mph) Saturation Flow (pcuphpl) Effective Length (ft, PCU) Response Time (seconds) Regional Core (AT=0) Original45230720.51.25 Updated60218524.01.37 CBD (AT=1) Original50235320.51.25 Updated65221324.01.37 Urban Business (AT=2) Original55239320.51.25 Updated65221324.01.37 Urban (AT=3) Original60242820.51.25 Updated65221324.01.37

29. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY29 Parameter Comparison Major Arterial Area TypeSettings Free Flow Speed (mph) Saturation Flow (pcuphpl) Effective Length (ft, PCU) Response Time (seconds) Regional Core (AT=0) Original25199020.51.25 Updated30176024.01.5 CBD (AT=1) Original30209820.51.25 Updated30176024.01.5 Urban Business (AT=2) Original35218320.51.25 Updated35183024.01.5 Urban (AT=3) Original35218320.51.25 Updated35183024.01.5

30. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY30 Parameter Comparison Local Street Area TypeSettings Free Flow Speed (mph) Saturation Flow (pcuphpl) Effective Length (ft, PCU) Response Time (seconds) Regional Core (AT=0) Original20184720.51.25 Updated25167124.01.5 CBD (AT=1) Original25199020.51.25 Updated25167124.01.5 Urban Business (AT=2) Original30209820.51.25 Updated30176024.01.5 Urban (AT=3) Original30209820.51.25 Updated30176024.01.5

31. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY31 Parameter Comparison Introduction of Slope Variation Slope-specific parameters not yet implemented in calibration model runs, but will be soon Modify response time and saturation flow Hold speed and effective length constant Do not modify parameters on freeway FTs Generally less steep Slope data does not reflect skyway and underpass elevation

32. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY32 Parameter Comparison Introduction of Slope Variation Example: Major arterial in CBD area type Uniform parameters: FFS = 30 mph, EL = 24 ft

33. SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY The End