Assessment and Refinement of Real-Time Travel Time Algorithms for Use in Practice May 9, 2007

Agenda

Detailed Corridor Study Results (60 min) Discussion on Remaining Tasks (30 min) ITS America Presentation (10 min) OTREC Proposal Status (10 min) Next Steps (10 min)

Study Results Outline

Data Collection Update Overall Error Analysis Algorithm Alternatives Summary Table – Statistics & conclusions Details & Recommendations I-5 and 217

Data Collection & Analysis Update Data collection complete for initial project

Collected on all freeways, spent approx $8K Approx 190 hours of driving, over 600 runs 311 runs analyzed (GIS, insert into db, calculate travel time) Data analysis has been time-consuming

High collection on I-5 corridor (N and S of downtown) 40 round-trips AM & PM

Intermediate collection on OR 217 and I-205 due to construction and disabled loops 20-30 round trips AM & PM

Low (baseline) collection on US 26 and I-405 10 round trips AM & PM

0

5

10

15

20

25

30

35

< -30 (-30, -20) (-20, 10) (-10, 0) (0, 10) (10, 20) (20, 30) > 30

% Error

% o

f R

un

s

Overall Error (all runs analyzed so far)

# runs: 331

Overall Average Absolute Error Percent: 10.8%

Algorithm Alternatives I-5 N SoD

0

10

20

30

40

50

60

70

80

0-10 10-20 20-30 >30

% Error

% o

f R

un

sMidpoint

San Antonio

WashDOT

Algorithm Alternatives 217 SB

0

10

20

30

40

50

60

0-10 10-20 20-30 >30

% Error

% o

f R

un

s

Midpoint

San Antonio

WashDOT

Error Percent – I-5 SoD and 217

0

5

10

15

20

25

30

35

40

45

50

<-30 -30-20 -20-10 -10-0 0-10 10-20 20-30 >30

% Error

% o

f R

un

s

I-5 N SoD

I-5 S SoD

OR-217N

OR-217S

Average Absolute Error Percent: 9.8%

Error Percents and ExpectationsSegment Avg Abs

Error-20% to +20%

-30% to +30%

I-5 N Carmen->Downtown 7.7% 93.2% 99.4%

I-5 S Terwilliger VMS -> Tualatin/Sherwood *

9.3% 84.7% 96.9%

I-5 S Terwil -> T/S Adj 7.1% 94.9% 99.7%

I-5 NB Downtown to River ** 8.7% 88.2% 98.7%

I-5 SB River to Downtown ** 15.7% 68% 94%

OR 217 NB 11.3% 85.9% 98.9%

OR 217 SB 12.6% 65% 98.9%

I-84 EB 11.6% 67.3% 85.9%

I-84 WB 17.1% 66.9% 85.6%

* Unadjusted lengths** Analysis of all runs not complete

Adjustments I-5 S Terwill – T/SStation

IdLocation Milepost Standard

Midpoint Len

Actual

ODOT Len

ODOT Adjust – Scale

1036 Hood Ave 299.25 0.2 (2.95) Not used 2.39

1108 Spring Garden 299.26 2.04 1 0.6

1107 Capital Hwy 295.18 1.45 1 0.6

1105 99W 293.36 1.04 1 0.6

1131 Haines St 293.2 1.06 1 0.6

1038 Upper Boones 291.25 1.35 1.5 0.9

1039 Lower Boones 290.4 0.94 2 1.2

1040 Nyberg 289.38 0.10 (2.23) 0.68 1.32

Total Len: 8.18 8.18 8.2

I-5 NB SoD Observations Problem areas

Capital – Terwilliger Sharp speed drop in this segment Possibly due to the curves

Terwilliger – Macadam Speed increases past Terwilliger Large spacing (2.37 miles)

Recommendation Add detection between Terwilliger and Macadam

Macadam

Terwilliger

Capital

Macadam

Terwilliger

Capital

capital

I-5 SB S of Downtown -Observations Problem Area

Haines – Upper Boones High errors runs all in PM peak Consistent speed drop Possibly caused due to merging/diverging

traffic from OR-217 Large detector spacing (1.85 miles)

Recommendation Add detector between Haines & Upper Boones

Also suggestion of problem between Haines & Capital

Upper Boones

Haines

22% (19% adj) under estimation of travel time

Speed drop between Haines & Upper Boones

Upper Boones

Haines

Capital

35% (23% adj) under estimation of travel time

OR 217 NB Accuracy problems worst in the afternoon Detector issues

Greenburg detector dropped out for several runs Runs missing Greenburg all have errors > 20%

Allen out for all runs Appears detectors have trouble in stop and go

conditions New detection not recommend Suggest considering historical data to address

changing conditions and detector dropouts

217 NB

Greenburg

Scholls

Denny

18% underestimation, 3:57 PM 4/19/97

Stop and go I-5 SB

Haines

OR 217 SB

Areas of concern Upstream of B-H Hwy, near Walker road (merge from 26

EB?) Scholls area – known bottleneck that activates between

Greenburg and Scholls Walker, Scholls detectors not functioning for all runs Need data when Walker & Scholls detectors are

functioning Accuracy may be fine if those detectors are functioinog Historical data can be used when detector drop out

217 SB

34% underestimation

BH Hwy

Walker

217 SB

16% underestimation

Hall

Greenburg

Scholls

Data Quality

How do the detectors fail? Communication errors Calibration errors Day-long failures?? Intermittent/sporadic failures?? Issues with stop and go? Overnight issues?

I-5 North of Downtown (NoD)

NB and SB segments between downtown and the Columbia River

NB – Initial Conclusions Data collected for this segment have encouraging error

rates Marine Drive detector malfunctioned during several runs. Additional data required for conclusions, this data has been

collected, needs to be analyzed SB – Initial Conclusions

Error rates are encouraging, but additional data required Area of concern around split between I-5 and I-205 Area of concern near lane drop north of Columbia

I-84 EB, I-84 WB

Conclusion – not enough detectors and detectors not stable enough to generate travel time estimates

Need additional detection before travel times can be provided

Project Results

Large amount of data collection and analysis Accuracy of current travel time predictions on all

corridors Evaluation of several algorithms (Coifman, WSDOT,

San Antonio, Midpoint) However, results generally inconclusive

Recommendations for corridors where travel time can be provided

Recommendations for infrastructure improvements Potential recommendation for influence area

adjustments

Project Phases

Initial Project (through June 07) OTREC – Phase 1 (July 2007 - Sept 2007)

$23,000 in funding Additional data analysis Some additional data collection (as needed) Real-time evaluation of travel time accuracy

FY02 (Oct 2007 – Sept 2008) Proposals due May 25 Have $34,000 in match left to use from original

project

OTREC FY02

Historical Data Apply historical data to

Detector Spacing Affect of detector spacing on travel time accuracy Initial work at PSU by Rob Bertini, also work by

Kwon Reviewers Interested In

Good set of metrics for accuracy Real-time quantification of accuracy

ITS America Presentation

Thoughts? Ideas? Comments?

Next Steps…

Continue analysis along lines of this presentation Comments?

OTREC FY02 Proposal Proposal Due May 25

Task 5: Detailed Comparative Study Proposed date: May 9 – next week? Draft Report: May 31

Final Report: June 30

EXTRAS

Macadam

Terwilliger

Capital

Extension – Phase I Promised

This project will produce the following three outcomes: Algorithm Recommendation The project will produce a

recommendation for an algorithm to be used for travel time estimation for the Portland area for display on DMS signs and availability on 511 and tripcheck.com.

Ground Truth Data Collection The project will produce a large collection of ground truth data which will be available to researchers in the OTREC consortium upon request. The project team is already aware of several projects including, PORTAL [8] and latte [13], which will be able to utilize the data collected.

Techniques for Evaluating Travel Time Accuracy The project will document a method for dynamically analyzing the accuracy of travel time estimates and evaluating when travel times are and are not accurate enough to be provided to travelers.

ITS America – Potential Outline Study Goals PORTAL Data Collection Analysis

What types of errors are we seeing Where are we seeing the errors What do we think is causing the errors

Algorithm Refinement Adjusting lengths of influence areas appears to make a

significant improvement

FOR KT’s reference

I-5 SB observations

See if can see where congestion clears – and adjust hood for that len

Around bertha/terw – bertha terw detector is 297.33

Hood is 299.25 spring is296.26 Segment starts at 298 So 298-297.33 – mile for hood?

Lower Boones

Haines

Pacific

Capital

I-5S

Run 215, 221 – looks as if detectors aren’t capturing stop and go

Two patterns when error – stop and go pattern and error hasn’t propagated to haines (i.e. 257) (416 also)

449 congestion past haines, 437 also, 451 also, 435

14 – uncaptured congestion between haines and upper boones, 28 ditto, 257, 259, 274, 416,

Hau says Galen wants

A. The accuracy of travel time estimation given the current instrumentation as well as using the current algorithm.

B. Adjustments and changes to the travel time estimation approach that will provide a greater amount of confidence to provide travel time to the public

C. Recommendations for where travel time should be provided and what needs to happen to make it happen across the entire metro area

D. Is the level of accuracy appropriate for dissemination via VMS, the web and phone.

Results of this Study

1. average error pct & std dev 2. based on those numbers & assumption of normal distribution, % errors expected to be < 20% and < 30% (like I put in task 4) 3. locations of potential bottlenecks 4. comments from reviewing the plots as to where errors occur most commonly 5. manually create a set of segment lengths based on two previous bullets and see if those lengths improve accuracy 6. results from different types of influence areas (wadot, etc.) 7. Recommendations for reducing error - Additional detectors etc. with location 8. Can travel times be displayed with current configuration?

What did we promise from this study? Investigate ITS data fidelity Ground Truth Data Collection Sensitivity Analysis of Algorithms Algorithm Refinement Detailed Comparative Study

accuracy of the algorithm to generate real-time travel times; reliability of the approach such as detailed information regarding

when the algorithm performs well, and understanding of factors that may contribute to unreliable travel times,

impact on hardware and / or software requirements; scalability of approach; and suitability for use in VMS, Web-based, and telephone traveler

information applications.

Kristins 217 NB Notes

503 – allen missing seems to be issue 505, 233, 235, 240 – detectors aren’t getting

stop and go 480 slowdown at certain detectors 231, 496 conditions changed 517 slowdown in between detectors 1001b no seq!!! Affects rtspeeds Error much worse when greenburg dropped

out

217 sb kt

Walker, scholls out for all runs 497, 473, 492, scholls would help 504, 232, 512, 518, 230 – walker would help 495 – unclear 520 – need walker and scholls

I-5 NB SoD KT

Overestimate when upper boones missing – why?

Most estimates are overestimates 3, 19 – capital-pacific 433, 254, 465, macadam, terwilliger 23 changing conditions 405, 273 stop and go