beyond gee-whiz statistics: guiding transportation investments with transportation system...
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Beyond Gee-Whiz Statistics:Beyond Gee-Whiz Statistics:
Guiding Transportation Investments Guiding Transportation Investments with Transportation System with Transportation System Performance MeasuresPerformance Measures
presented bypresented by
Richard Margiotta, PrincipalRichard Margiotta, PrincipalCambridge Systematics, Inc.Cambridge Systematics, Inc.
November 6, 2003November 6, 2003
Presentation OverviewPresentation Overview
Why Bother With Performance Measures?Why Bother With Performance Measures?
Where We’ve BeenWhere We’ve Been
Advances in Metrics and DataAdvances in Metrics and Data
Opportunities for Performance Measures to Guide Opportunities for Performance Measures to Guide Investment -- Focus on Operations investmentsInvestment -- Focus on Operations investments
Congestion Performance: Why Bother?Congestion Performance: Why Bother?
Sound Business PracticeSound Business Practice
• Private sector has embraced performance measures as a Private sector has embraced performance measures as a way to:way to:
- Better serve customersBetter serve customers
- Assess return on investmentAssess return on investment
• ““Know where you are before you decide where to go”Know where you are before you decide where to go”
Use of Performance Measures Becoming More Widespread and Use of Performance Measures Becoming More Widespread and Accepted as Best PracticeAccepted as Best Practice
• Well established in pavement and bridge managementWell established in pavement and bridge management
• Service-oriented measures increasingly being used in State Service-oriented measures increasingly being used in State and MPO Long Range Plansand MPO Long Range Plans
Why Bother? (cont.)Why Bother? (cont.)
AccountabilityAccountability
• Broader customer base for performance measuresBroader customer base for performance measures
• Decision-makers and public becoming increasingly more Decision-makers and public becoming increasingly more interested in “how are we doing?”interested in “how are we doing?”
Becoming easier to do with new technologiesBecoming easier to do with new technologies
Challenges: Challenges:
• How to apply concepts worked out in private sector and How to apply concepts worked out in private sector and transportation planning to real-time Operationstransportation planning to real-time Operations
• Moving beyond simple reporting of trendsMoving beyond simple reporting of trends
Where We’ve BeenWhere We’ve Been
Performance measures have always been used to some degree Performance measures have always been used to some degree in transportation planning, but at a simplified scale…in transportation planning, but at a simplified scale…
• V/C, travel time/delay studiesV/C, travel time/delay studies
… … But suffer from data problemsBut suffer from data problems
• Indirect measurement (traffic volumes as a surrogate)Indirect measurement (traffic volumes as a surrogate)
• Travel demand forecasting modelsTravel demand forecasting models
• Small samples, infrequent surveysSmall samples, infrequent surveys
ADVANCES IN DATA AND METRICSADVANCES IN DATA AND METRICS
What Are We Measuring?What Are We Measuring?
Congestion Congestion
• What happens on facilitiesWhat happens on facilities
MobilityMobility
• What happens to users -- how they experience the What happens to users -- how they experience the transportation system (trips)transportation system (trips)
AccessibilityAccessibility
• Interaction of transportation system and activities Interaction of transportation system and activities (opportunities)(opportunities)
Congestion and Mobility can use similar metricsCongestion and Mobility can use similar metrics
Metrics for Performance MonitoringMetrics for Performance Monitoring
System performance tracked at the level of the user (trip) System performance tracked at the level of the user (trip) and facility (corridor)and facility (corridor)
Understandable to professionals and publicUnderstandable to professionals and public
Multiple metrics to capture full rangeMultiple metrics to capture full range
Existing data and methods, preferably through continuous Existing data and methods, preferably through continuous monitoring monitoring
Integration with other transportation functionsIntegration with other transportation functions
Travel Time(route segments or trips)
Performance Measures
average travelspeed (mph)
travel time(min)
travel rate(min/mile)
indices•travel rate index•traffic temperature•congestion severity
delay (min)• per vehicle• per person• per VMT• per driver
roadway characteristicsideal travel conditionsvolumes
probe vehicles instrumented cars ITS roadway equipment
Special Studies
short-termtraffic counts
forecastingmodels
transformation
ContinuousSpecial StudiesContinuous
spot speeds
models
volumes Post-processors(IDAS)
Indirect Measurement/ModelingDirect Measurement
absolute measures
relative measures
Performance Measures Should Encompass Performance Measures Should Encompass Multiple DimensionsMultiple Dimensions
DISTANCEDISTANCE
SOURCESOURCE
DailyDaily
Late NightLate Night
P.M. PeakP.M. Peak
Mid-DayMid-Day
A.M. PeakA.M. Peak
Early A.M.Early A.M.
IncidentsIncidents
Work ZoneWork Zone
BottleneckBottleneck
WeatherWeather
DemandDemand
Special EventsSpecial Events
TCD’sTCD’s
Segm
ent
Segm
ent
TripTrip
Corridor
Corridor
Areaw
ide
Areaw
ide
DailyDailyHistoriesHistories
DetectionDetection
TIMETIME
TrendsTrends
Recommended Measures: BasicRecommended Measures: Basic
Travel Rate Index (TRI)Travel Rate Index (TRI)
ratio of:ratio of: travel rate in peaktravel rate in peakideal travel rateideal travel rate
Delay per DriverDelay per Driver
Percent of Congested Travel Percent of Congested Travel
• %VMT where speeds < 45 mph (fwy)%VMT where speeds < 45 mph (fwy)
Travel Time Reliability: DefinitionTravel Time Reliability: Definition
Measured by how travel time of a trip varies from one time period Measured by how travel time of a trip varies from one time period to anotherto another
• In other words, reliability is measured as the variability of travel In other words, reliability is measured as the variability of travel timestimes
• ““How long will my trip take today compared to the same trip at How long will my trip take today compared to the same trip at the same time on any average day?”the same time on any average day?”
OROR
• Ability of travelers to predict travel time for a trip and to arrive Ability of travelers to predict travel time for a trip and to arrive at destination within an “on-time window”at destination within an “on-time window”
Variability caused by the “Seven Sources” of congestionVariability caused by the “Seven Sources” of congestion
Categories of Reliability MeasuresCategories of Reliability Measures
There are three categories of reliability There are three categories of reliability measuresmeasures
• StatisticalStatistical
• Buffer timeBuffer time
• ““Tardy arrival”Tardy arrival”
Travel Time Distribution and Travel Time Distribution and Reliability MeasuresReliability Measures
FrequencyFrequency
Buffer TimeBuffer Time Tardy TripsTardy Trips
Mean Travel TimeMean Travel Time
On-Time PerformanceOn-Time Performance
Statistical MeasuresStatistical Measures
Buffer IndexBuffer Index
Weighted average of . . .Weighted average of . . .
The extra time needed to arrive on timeThe extra time needed to arrive on time
Seems to resonate with practitionersSeems to resonate with practitioners
95th %Travel Rate
Average Travel Rate
Average Travel Rate
Measuring ReliabilityMeasuring Reliability
Field measurementField measurement
• Requires many samples or, ideally, continuous measurementRequires many samples or, ideally, continuous measurement
• Roadway performance versus trip performanceRoadway performance versus trip performance
- Different technologies and measurement scaleDifferent technologies and measurement scale
• Hard to separate out Hard to separate out ““root causesroot causes”” due to complex interactions due to complex interactions
- Requires combination of travel time and Requires combination of travel time and ““eventevent”” data data
Modeling methodsModeling methods
• Tend to regress to average conditionsTend to regress to average conditions
• May be useful in decomposing reliability into sourcesMay be useful in decomposing reliability into sources
Intermediate or Surrogate Performance MetricsIntermediate or Surrogate Performance Metrics
Examples:Examples:
• Incident duration and “timeline”Incident duration and “timeline”
• Clearance time for snowy roadsClearance time for snowy roads
Easier to developEasier to develop
More understandable to professionMore understandable to profession
BUTBUT
Don’t get to the bottom-line as effectively as travel time Don’t get to the bottom-line as effectively as travel time measuresmeasures
The “Family Tree” of Performance MeasuresThe “Family Tree” of Performance Measures
ClearanceClearanceClearanceClearance
Total Total DelayDelay
ReliabilityReliability(Variability)(Variability)
““Nonrecurring”Nonrecurring”DelayDelay
AgencyAgencyResponseResponse
ororEvent-Event-
RelatedRelated
ThroughputThroughput
IncidentIncident
Total DurationTotal Duration
DetectionDetection ResponseResponse
Work ZoneWork Zone
Total DurationTotal Duration
During PeakDuring Peak
Weather Weather
TotalTotalDurationDuration
ResponseResponse
““Recurring”Recurring”DelayDelay
(Bottleneck)(Bottleneck)
UserUserImpactsImpacts
Data Issues Associated With Detailed Data Issues Associated With Detailed Performance MeasuresPerformance Measures
Secondary Use of Operations a tremendous data source, BUT…Secondary Use of Operations a tremendous data source, BUT…
Limited primarily to freeways in major urban areasLimited primarily to freeways in major urban areas
Archiving and data quality are problematicArchiving and data quality are problematic
Measurement limited to facility performance or “corridor-trips”Measurement limited to facility performance or “corridor-trips”
Comparability of measures calculated from continuous Comparability of measures calculated from continuous Operations data vs. “traditional” or “synthetic” methodsOperations data vs. “traditional” or “synthetic” methods
OPPORTUNITIES TO GUIDE INVESTMENTOPPORTUNITIES TO GUIDE INVESTMENT
Performance Measures Can Be Applied At Performance Measures Can Be Applied At Several Levels of InterestSeveral Levels of Interest
Real-Time OperationsReal-Time Operations
• What is happening now; expected to happen shortlyWhat is happening now; expected to happen shortly
• How do we respond to travel/system conditions; what How do we respond to travel/system conditions; what strategies do we implement?strategies do we implement?
- Incident response, traveler information (esp. advanced Incident response, traveler information (esp. advanced guidance)guidance)
Operations PlanningOperations Planning
• What we expect to happen next week/next monthWhat we expect to happen next week/next month
• How can we adjust our strategies to be more responsiveHow can we adjust our strategies to be more responsive
- New coordination plans, pre-deployment, routing plansNew coordination plans, pre-deployment, routing plans
Performance Measures Can Be Applied At Performance Measures Can Be Applied At Several Levels of InterestSeveral Levels of Interest
Short-Term Planning and Programming - 1-5 years (TIP, ITS Short-Term Planning and Programming - 1-5 years (TIP, ITS Deployment Plans and Architectures)Deployment Plans and Architectures)
Long-Term Planning - 5-20 years (Long-Range Plans)Long-Term Planning - 5-20 years (Long-Range Plans)
Expected impacts on the “family” of performance measures can Expected impacts on the “family” of performance measures can help in deciding priorities and trade-offshelp in deciding priorities and trade-offs
• Models need to be sensitive to performance measures, Models need to be sensitive to performance measures, especially reliability and the “Seven Sources” especially reliability and the “Seven Sources”
Measuring Reliability Measuring Reliability (continued)(continued) Atlanta, GeorgiaAtlanta, Georgia TrTI/Buffer Index by Time-of-DayTrTI/Buffer Index by Time-of-Day
0.000.00
0.200.20
0.400.40
0.600.60
0.800.80
1.001.00
1.201.20
1.401.40
0:000:00 2:002:00 4:004:00 6:006:00 8:008:00 10:0010:00 12:0012:00 14:0014:00 16:0016:00 18:0018:00 20:0020:00 22:0022:00 0:000:00
Time of Day (Average Weekdays Only)Time of Day (Average Weekdays Only)
Index Value or Index Value or Congested Travel (1.0=100%) Congested Travel (1.0=100%) Travel Time IndexTravel Time Index
Buffer IndexBuffer Index
Orlando Eastbound I-4, Evening Peak Period, Weekdays
0
1
2
3
4
5
6
1 11 21 31 41 51 61 71
Days
Tra
ve
l Ra
te (
Min
ute
s p
er
Mile
)
SUMMARYSUMMARY
MetricsMetrics
• Numerous travel-time based metrics are available Numerous travel-time based metrics are available
• Local conditions will indicate which ones are best, but Local conditions will indicate which ones are best, but multiple metrics should be used to meet a variety of needsmultiple metrics should be used to meet a variety of needs
• Summary metrics good for “report card”Summary metrics good for “report card”
• Decomposing metrics by at least 3 dimensions is very useful Decomposing metrics by at least 3 dimensions is very useful for investment decisionsfor investment decisions
- Time/Space/SourceTime/Space/Source
- Reliability becoming increasingly importantReliability becoming increasingly important
• ““Family Tree” of metrics, with output measures at the Family Tree” of metrics, with output measures at the bottom feeding into user-based measures should be bottom feeding into user-based measures should be developeddeveloped
SUMMARY (cont.)SUMMARY (cont.)
Data to Support MetricsData to Support Metrics
• Operations sources can provide the data to support this Operations sources can provide the data to support this level of detail, but barriers existlevel of detail, but barriers exist
- Data quality, coverage, consistencyData quality, coverage, consistency
• Models do not now provide emerging performance metrics, Models do not now provide emerging performance metrics, especially Reliabilityespecially Reliability
Investment Decisions Investment Decisions
• Currently, short-range decisions most easily supportedCurrently, short-range decisions most easily supported
• Profession needs to evolve toward a broader framework Profession needs to evolve toward a broader framework using the full range of performance measures for all levels using the full range of performance measures for all levels of investment, from the “here and now” to long-range of investment, from the “here and now” to long-range planningplanning
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