assessment and refinement of real-time travel time algorithms for use in practice

Assessment and Refinement of Real-Time Travel Time Algorithms for Use in Practice Nov 8, 2006

Outline

Ramp Meter Data Fidelity Assessment Inrix Data Update Data Collection Plan Travel Time Best Practices Results Schedule update

Ramp Meter Data Fidelity Assessment Impacts of Various Factors on Travel Time

Estimation Accuracy Algorithms Detector Spacing Data Quality

Algorithm Comparison: Uncongested Runs

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I-5 N(217-405)

I-5 S (Bridge-84)

I-5 S(405-217)

217 S I-205 S(84-O.City)

I-84 E(5-205)

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Algorithm Comparison: Congested Runs

I-5 SB (405-217)

217 N 217 S I-205 N(5-O.City)

I-5 NB (84-Bridge)

I-5 S (Bridge-84)

I-84 E(5-205)

Large detector spacingSome probe runs encountered an incidentSignificant recurring congestion

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8:11:00 8:13:00 8:15:00 8:17:00 8:19:00 8:21:00 8:23:00

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Algorithms: Trajectory Comparison

Conclusions - Algorithms

FHWA says 90% accuracy is ideal, accuracy must be no less than 80% (Agrees with what we discussed last time)

No algorithm is consistently better and consistently < 10%

Many runs have error > 10% Appears to be associated with large detector spacing and

incidents Need more data to verify impacts of algorithms, spacing, etc.

Moderate impact from algorithm, but probably not enough to overcome infrastructure issues (more when we examine other states practices)

Detector Spacing Impacts-Analytical More detector stations => more data samples Lower error due to more samples If one detector has issues, others will mitigate

that problem Shockwave Propagation

When an incident/bottleneck occurs far from a detector, it takes time for the congestion to reach the detector

Shockwave propagation 12-16 mph, 15 mph = 4 minutes/mile

2 miles

1.5 miles = approx. 6 minutes

Detector 1

Detector 2

Bottleneck

Detector Spacing Impacts: Congested Conditions

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I-205 NB – Stafford – MP 3.55 – Lane 2

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I-5 NB – Delta Park – MP 306.51 – Lane 2 speed

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Conclusions – Detector Spacing and Data Quality Detector Spacing

Expect and think we see association with detector spacing Need more data to verify Are also creating an analytical model for detector spacing

impacts

Data quality Suspect there is an impact Need more data to verify Would like to clarify speed calculation procedure

Inrix Data

Provide flow and travel time data XML data stream

Data Sources Current data is a processed version of the ODOT

Region 1 loop detector data As of mid-November, probe data will be included

(transponder detectors from instrumented fleets (taxis, etc.))

Data Validation

Inrix has validated accuracy of their data for three east-coast cities The networks in these cities use probe data only Validation not valid for Portland (different city,

probe + detector data) Potential good source of data, but do not

believe we can use it as ground truth without more validation

We are getting sample data (NDA in process) Meeting with Inrix Technical Staff?

Ground Truth Data Collection – Phase 1 Initial Study to confirm methodology and

process Issues:

Collection Process Corridor selection - focus on two corridors for this

phase Number of Runs Timing of Runs

Quality Counts

Recommended by ODOT personnel $45/hour + mileage (currently ~$0.49/mile) We provide list of highways, hours, and a list

of locations on the highways that we want timed

They use a stopwatch and record the time when they pass each specified location

Corridor Selection

Corridor Selection Criteria Moderate-severe recurrent congestion Variable loop detector spacing (some low some

high) to allow evaluation of spacing effects Some situations with high data quality Construction Schedule – avoid times/areas when

there is construction Propose:

OR 217 (‘good’ conditions) I-205 or I-5 (more variable detector spacing)

Credit to Sue Ahn for her ideas for corridor selection in SWARM

217 N, Weekdays - April, 2006

traffic flow

217 S, Weekdays - April, 2006

traffic flow

217 Notes

Congestion: moderate congestion both NB and SB Congestion NB and SB in both AM and PM Peaks PM congestion generally worse than AM SB congestion generally worse than NB

Detector Spacing: good NB: 9 stations SB: 11 stations Length: ~7 miles

Data Quality 217 N - ~1% disqualified data 217 S - ~2% disqualfied data

Timing & Cost Specifics – 217 PM Peak 217 S

Peak: 3:00-6:00 Min/Max/Avg TT: 14.3/25.0/20.5 min 217 N:

Peak: 4PM – 6PM Min/Max/Avg TT:10.2/14.2/12 min Average Round trip ~32 minutes Need ~50 runs for 5% error at 95% confidence

Start with 20 runs/corridor 2 runs/hr, 10 hrs = 20 runs = $450 ($45/hr) Gas cost: 20 runs * 7 miles * 0.5/mile = $70

Data from weekdays – April, 2006

Timing – 217 AM Peak AM Peak

217 N Peak: 7:30-8:15 Min/Max/Avg TT: 8.2/10.6/9.3 min

217 S: Peak: 7:00-9:00 Min/Max/Avg TT:12.5/20.7/16.1 min

Avg round trip time ~25 min Data from weekdays – April, 2006 Similar costs $500 for 20 runs

Detector Locations - 217

I-205 N, Weekdays – October, 2006

traffic flow

Detector spacing poor before mp 8

I-205 S, Weekdays – October, 2006

traffic flow

Detector spacing poor after mp 8

Detector Locations I-205

SB Stark/Washington mp 20.34

SBClackamas Hwy mp 12.67

SBJohnson Creek mp 16.24

I-205 Notes Detector spacing is poor for mileposts 0-8

Do not collect data on that portion of 205 – means can not capture the congestion that occurs there

Consider collecting mp 13 – mp 20 Congestion:

Some congestion on northern end of I-205 NB and SB, AM and PM peaks

NB AM congestion appears worst Detector Spacing:

See Map Data Quality

I-205 NB - ~1% disqualified data I-205 SB - ~2% disqualified data

I-5 N Weekdays – October, 2006

traffic flow

I-5 S, Weekdays – October, 2006

traffic flow

Detector Locations I-5 S of Downtown

NB, Nyberg, mp 289.4

NB, Macadam, mp 299.7

Detector Locations I-5 N of Downtown

NB, Macadam, mp 299.7

SB, Swift/Marine, mp 307.35

I-5 Notes Congestion:

N of Portland: SB congestion in AM and PM peaks, NB congestion PM peak

S of Portland: Minimal SB congestion, NB congestion through curves in AM peak

NB PM congestion (going over the bridge) appears worst More severe congestion than 205

Detector Spacing: Variable - See Map

Data Quality I-5 NB - ~2% disqualified data I-5 SB - ~4% disqualified data

Milwaukee, WI

Detector Spacing 0.25 miles in urban areas 2 miles in rural areas

Data from detectors transmitted to TOC Center Freeway Traffic Management System (FTMS) Server

Travel Time = Known Distance/Average Speed Website updated every 3 minutes DMS signs updated every 1 minute No probe vehicle data; all detector derived travel times

Other States – Best Practices…

San Antonio, TX

Travel Times calculated from/to major interchanges Detectors

Loop Detectors Video Detectors

Point travel speeds used to calculate travel times from detector to detector Segment travel speed is the lower of u/s and d/s speed Point to point travel times are summation of segment travel times

Travel times posted on TransGuide website use the same algorithm

Chicago, IL DMS Travel Times

From three sources (IPASS, RTMS, Loops) GCM Webpage

Only IPASS travel times IPASS Data

Travel times from toll plaza to toll plaza Based on toll transponder data collected by ETC system > 1.5 million users on tollways Significant number of probe vehicles provide time stamp and

location Travel times calculated using location and time stamp

information High quality of data

RTMS Data IDOT Loop detector data

Houston, TX

Vehicle Probes with transponder tags Readers collect data as vehicles pass

2-3 miles apart Time Location of probe

Software Average Speeds Average Travel Times Transtar website DMS

Updated every 10 minutes

Nashville, TN RTMS detectors

0.25 mile spacing Speeds Ensure data quality by regular calibration CCTV cameras

Travel Time verification

Data Collection & Processing Average speed from RTMS every 2 minutes Travel time calculation

average speed and distances between sensors Travel Times automatically posted to the DMS by TMC software Travel Times are only reported for segments < 5 miles

Atlanta, GA

VDS Cameras Monitoring and Video Detection Cameras Fixed black and white cameras Placed along all major freeways Provide volumes and speeds

Travel Times between 6 a.m. – 9 p.m. Average speeds from Video Detection Cameras

Software Automatic message generation for DMS

San Francisco, CA

Existing Caltrans System Dual Loop Detectors

Speeds

New MTC System Antennas to read FasTrak Toll Tags Average Travel Times and speeds of all vehicles

511 System Combination of data from both sources to calculate travel times

Other Cities

www.smartroute.com Real Time Traveler Information

Boston Miami St. Louis North Carolina New Jersey

Summary

Two main approaches for generating travel times In house

Loop Detectors High Density (0.25 mile spacing)

Video Detectors RTMS Toll Tags

Private providers Smartroute Systems Inrix

Schedule Update…

217 N/S Peak Pictures

217 N, AM Peak Weekdays - April, 2006

traffic flow

217 N, PM Peak Weekdays - April, 2006

traffic flow

217 S, Weekdays, AM Peak - April, 2006

traffic flow

217 S, Weekdays, PM Peak - April, 2006

traffic flow

I-84 (East and Westbound) Limited number of loop detectors and poor data quality

I-405 (North) Relatively short (≈ 3.5 miles) and limited loop detectors

I-405 (South) This freeway corridor is relatively short (≈ 3.5 miles), lightly congested during peaks

US-26 (East and Westbound) Was under construction – what is data quality like on 26?

OR217 Northbound Sue had problems with the queue location – when are we getting detectors again?

OR217 Southbound Looks pretty good – when are detectors going to be turned on?

I-205 Northbound Looks pretty good. When are new loop detectors going in?

I-205 Southbound This corridor is lightly congested during the peak periods. The speed remains above 40 mph throughout the entire corridor.

I-5 Upper-section Northbound Poor data quality

I-5 Upper-section Southbound Poor data quality??

I-5 Lower-section Southbound A recurrent bottleneck is located near the Wheeler Ave. on-ramp. The resulting queue, however, usually propagates only 2 – 3 miles

upstream. A queue that forms near Wheeler Ave. often overrides the upstream bottleneck near Columbia Blvd (in the upper-section of I-5). In

this case, the entire queue propagates upstream of the Interstate bridge, where loop detector data are not available to PSU. I-5 Lower-section Northbound

There are several of sections along this corridor where the spacing of adjacent loop detectors is very large. 2.5 miles between Terwilliger Blvd. and Macadam Ave., 3 miles between Nyberg Rd. and Stafford Rd.

Data Quality Flags

Data is flagged as invalid if it meets any of the following criteria (adapted from TTI criteria) 20 second count > 17 Occupancy > 95% Speed > 100 MPH Speed < 5 MPH (probably being removed) Speed = 0 and Volume > 0 Speed > 0 and Volume = 0 Occupancy > 0 and Volume = 0

Data quality is determined (in part) by percentage of 20-second readings for which a detector fails one of the above tests

I-5 Lower Northbound 217 Southbound I-205 Northbound I-205 Southbound

Implemented February, 2006 November, 2005 December, 2005 December, 2005

Length of study section 17 miles 7 miles 19 miles 19 miles

Number of loops 51 24 46 46

Number of on-ramps (with loops) 16 12 9 18

Level of congestion: pre SWARM (duration, queue length, low speed)

(2-3 hrs, 6 miles, 25-35mph) (2-4 hrs, 4-6 miles, ~25mph) (2-3 hrs, 5 miles, ~30mph) (2 hrs, 4-6 miles, ~35mph)

Level of congestion: post SWARM (duration, queue length, low speed)

(2-3 hrs, 6 miles, 25-35mph) (2-4 hrs, 4 miles, ~25mph) (2-3 hrs, 5 miles, ~30mph) (2 hrs, 3-5 miles, ~40mph)

Queue contained within corridor? (pre SWARM, post SWARM)

AM: (Yes, Yes) PM: (Yes, Yes)

AM: (Yes, Yes) PM: (Not clear, Not clear)

AM: (Not clear, Not clear) PM: (Not clear, Not clear)

AM: (Yes, Yes) PM: (Yes, Yes)

Coverage of loop detectors (miles/loop station)

1.14 (max: 3.1) 0.74 (max: 1.2) 1.1 (max: 1.9) 1.46 (max:4.3)

Data quality (Avg % good readings, Min %)

(94.2, 21.8) (99.2, 98.9) (98.0, 94.8) (98.3, 85)

No. of Loops < 90% 3-7 0 0 1-2

Construction schedule Late summer of 2006

Uncongested Conditions

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OTHER STATES

Milwaukee, WI

Introduction

DMS Usage Travel Times Incidents Amber Alerts Special Events Construction and Weather Information Congestion Information

36 DMS signs present on Arterials and Freeways

Source: Kelly Langer: Keeping Wisconsin Moving – An Overview of WisDOT’s DMS Travel TimesNTOC Presentation, September 28th, 2005

Technology & Data Processing Detector Spacing

0.25 miles in urban areas 2 miles in rural areas

Data from detectors transmitted to Traffic Operations Center

Freeway Traffic Management System (FTMS) Server Travel Time = Known Distance/Average Speed

Website updated every 3 minutes DMS signs updated every 1 minute No probe vehicle data; all detector derived travel times

Travel Times - Report

San Antonio, TX

Introduction

Travel Times calculated from/to major interchanges Detectors

Loop Detectors Video Detectors

Point travel speeds used to calculate times from detector to detector based on distance between detectors

Travel times displayed on mainlane DMS from 6:00 a.m. to 10:00 p.m., seven days of the week

Travel times posted on TransGuide website use the same algorithm

Data Calculation

Segment Segment Speed Travel Time

(MPH) (Minutes)1 55 0.552 47 0.643 47 0.644 45 0.675 30 1.006 30 1.007 30 1.008 25 1.209 20 1.5010 15 2.0011 15 2.00

TOTAL 12.19

Travel Time Calculation-

- Segment travel speed is chosen as lower of upstream and downstream sensor speed

- Point to point travel speed is summation of segment travel times

Source: San Antonio TransGuide Travel Time Algorithm

DMS Display & Accuracy

Time of Day Non Peak

Travel time messages appear alone Peak Periods

Travel times in combination with congestion warnings Incidents

Travel times messages automatically overridden

Accuracy Tests indicate 85% accuracy within predicted travel time range Predictive algorithm tests showed low benefit for additional cost

Chicago, IL

Introduction

~33 DMS on tollways and DOT roads DMS messages

Incident alerts Amber alerts Travel time messages

Travel Times provided on tollways by ISTHA I-294 Tri-State Tollway (Indiana to Wisconsin) I-90 Northwest Tollway (Chicago to Wisconsin) I-88 East-West Tollway (Tri-State Tollway to Rock Falls, Illinois) I-355 North-South Tollway, extending north seventeen miles from

I-55 Stevenson Expressway

Technology

IPASS Data Travel times from toll plaza to toll plaza Based on toll transponder data collected by ETC system > 1.5 million users on tollways Significant number of probe vehicles provide time stamp and

location Travel times calculated using location and time stamp

information High quality of data

RTMS Data IDOT Loop detector data

Travel Time Estimation

Toll network Roadway segments Bounded by ramps and plazas

IPASS & RTMS data Provide redundancy on certain segments Travel time software allows choice of data

DMS Travel Times From all three sources (I-PASS, RTMS, Loops)

GCM Webpage Only I-PASS travel times

Real Time Speed Map

Travel Times - Report

Houston, TX

Introduction

DMS Signs Message Hierarchy Incidents Construction/Pre Construction Amber Alerts Travel Times Special Events Safety Campaigns

81 DMS locations

Source: www.ops.fhwa.gov/publications/travel_time_study/houston/houston_ttm.htm

Technology

AVI Toll Transponders Approximately 2 million transponders Data collected at 232 reader stations and transmitted to Transtar

TMC Reader stations 2-3 miles apart

Automated Travel Time Processor Posts travel times to 81 DMS signs every 10 minutes (5:30 a.m.

– 7:30 p.m.) Some signs updated more frequently than others

Data Collection and Processing Vehicle Probes with transponder tags

Readers collect data as vehicles pass Time Location of probe

Software Average Speeds Average Travel Times Transtar website DMS

Source: www.ops.fhwa.gov/publications/travel_time_study/houston/houston_ttm.htm

Real Time Speed Map

Real Time-Travel Times

Nashville, TN

Introduction

20 DMS Signs 2 signs display travel time Travel times displayed through the day unless incidents occur

Source:http://www.ops.fhwa.dot.gov/publications/travel_time_study/nashville/nashville_ttm.htm

Technology, Data Collection & Processing Technology

RTMS detectors at 0.25 mile spacing Speeds Ensure data quality by regular calibration

CCTV cameras Travel Time verification

Data Collection & Processing Average speed from RTMS every 2 minutes Travel time calculation

average speed and distances between sensors Travel Times automatically posted to the DMS by TMC software

Travel Time Facts

Travel Times provided in 2-3 minute ranges Allows for +/- 1-1.5 minutes variation in travel times

Incident messages override travel times\ Travel Times are reported only for segments < 5 miles

Real Time Travel Times

Atlanta, GA

Introduction

Changeable Message Signs (CMS) All major freeways HOV CMS

Information for express lane commuters Automatic message generation Travel Times between 6 a.m. – 9 p.m.

Average speeds from Video Detection Cameras Incident Messages

Incident location Number of lanes affected

Technology

VDS Cameras Monitoring and Video Detection Cameras Fixed black and white cameras Placed along all major freeways Provide volumes and speeds

Source: http://www.georgia-navigator.com/about.shtml

Real Time Speed & Travel Times

Travel Times - Web

San Francisco - Bay Area, CA

Introduction

Real Time Information (traffic.511.org) Traffic Conditions Travel Times Incident Reports

Technology

Existing Caltrans System Dual Loop Detectors

Speeds

New MTC System Antennas to read FasTrak Toll Tags Average Travel Times and speeds of all vehicles

511 System Combination of data from both sources to calculate travel times

Travel Times Coverage

-80: SF (US-101) to Suisun City (Hwy 12) including the Carquinez & Bay Bridges

I-880: Oakland (I-80) to San Jose (I-280) I-680: San Jose (US-101) to I-80 including the Benicia

Bridge I-580: San Rafael (US-101) to the Alameda County line

(I-205) including the Richmond Bridge I-280: SF (6th St.) to San Jose (I-680) I-780: Vallejo (I-80) to Benicia (I-680) I-980: I-880 to I-580 I-238: I-880 to I-580 US-101: SF (GG toll plaza) to Santa Rosa (Hwy 12)

including the Golden Gate Br. US-101: SF (I-80) to San Benito County line Hwy 92: Hayward (I-880) to Half Moon Bay (Hwy 1)

including the San Mateo Bridge Hwy 85: Mountain View (US-101) to San Jose (US-101) Hwy 84: East Palo Alto (US-101) to Newark (I-880) Hwy 24: Oakland (I-580) to Walnut Creek (I-680) Hwy 4: Hercules (I-80) to Antioch (Hwy 160) Hwy 17: San Jose (I-280) to Santa Cruz County line Hwy 13: I-580 to Hwy 24 Hwy 37: Novato (US-101) to Vallejo (I-80) Hwy 87: US-101 to Hwy 85 Hwy 242: I-680 to Hwy 4 Hwy 1: Half Moon Bay (Hwy 92) to Montara (coming

soon)

Travel Times -Web