Guide to Establishing Monitoring Programs for Travel Time Reliability (2014) / Chapter Skim
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From page 151... ...
149 OVERVIEW This appendix supports the discussion presented in Chapter 2 and provides more detailed examples of the fi ve general types of tables commonly used for storing and managing data in a travel time reliability monitoring system (TTRMS)
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From page 152... ...
150 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY facility (usually marked by postmiles) , so that the physical distance between sensors can be computed.
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From page 153... ...
151 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY monuments are defined that function the same as AVI tag readers. The raw AVL data are message packets containing the latitude, longitude, speed, and heading of the vehicle at some sampling rate, often every few seconds.
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From page 154... ...
152 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TRAVEL TIME INFORMATION The information in the raw data tables needs to be processed so that travel time information can be developed for each segment, route, and time period. For infrastructurebased sensors, estimating travel times requires imputing missing data values, computing speeds from volume and occupancy values, and extrapolating point speeds over spatial segments to derive travel time information.
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From page 155... ...
153 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TABLE A.6. 30-SECOND INFRASTRUCTURE-BASED DATA WITH IMPUTATION Column Field Description 1 Time ID Time stamp for the 30-s period.
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From page 156... ...
154 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Automated Vehicle Identification Data This section shows three sample database tables designed to store AVI information derived during the processing of trip time information. The database tables would contain travel times that have been extracted from raw trip times collected by AVI sensors.
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From page 157... ...
155 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TABLE A.12. 5-MINUTE AVI-BASED REPRESENTATIVE SEGMENT OR ROUTE TRAVEL TIMES Column Field Description 1 Time ID Time stamp of the 5-min period.
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From page 158... ...
156 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Data Fusion For routes monitored by more than one technology type, data fusion can be used to improve the accuracy of the travel time information derived from a single technology. Data fusion requires travel time data from the individual sensor types to be aggregated to the same temporal and spatial level.
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From page 159... ...
157 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TABLE A.16. FUSED HOURLY SEGMENT OR ROUTE TRAVEL TIME SUMMARIES Column Field Description 1 Time ID Time stamp of the hourly period.
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From page 160... ...
158 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY RELIABILITY SUMMARIES Some summary database tables are useful for storing highly aggregated reliability measures. In terms of temporally aggregated measures, these are tables that store, for a given route, reliability information for a single calendar month, a quarter, or a year.
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From page 161... ...
159 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TABLE A.19. QUARTERLY REGIONAL-LEVEL RELIABILITY SUMMARY TABLE Column Field Description 1 Time stamp Quarter and year.
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From page 162... ...
160 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY • A defined plan for collecting work zone information, including the data source, the types of data needed, how they will be obtained, and the frequency of data collection; • A defined plan for collecting special event information, including the data source, the types of data needed, how they will be obtained, and the frequency of data collection; • A defined plan for collecting traffic control information, including the data source, the types of data needed, how they will be obtained, and the frequency of data collection; • A defined plan for measuring or estimating demand and demand fluctuations; • A defined plan for measuring capacity and determining if it is inadequate; • A defined plan for collecting data on exogenous events (optional) ; • A defined plan for collecting transit-specific data from AVL-equipped vehicles (optional)
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From page 163... ...
161 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY • Clearly specified methods for tracking the imputation measure used on a data point; • Clearly specified methods for storing metadata on what percentage of data points have been imputed and how they have been imputed to evaluate the statistical validity of reliability estimates; and • Clearly specified methods for imputing reliability measures in locations that lack detection technologies (optional)
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From page 164... ...
162 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Systems Interactions • A list of applicable intelligent transportation system (ITS) standards to which the system must adhere, with clearly specified methods for adhering to these standards (optional)
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From page 165... ...
163 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Interoperability: Allows system components from different vendors to communicate with each other to provide system functions and work together as a whole system. Message: Groupings of data elements that include information about how the data elements are combined and used to convey information among ITS centers and systems.
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From page 166... ...
164 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TABLE A.21. ADDITIONAL ITS STANDARDS Standard Author Organization and Location Summarya Standard Specifications for Archiving ITSGenerated Traffic Monitoring Data ASTM Available for purchase from ASTM website Specifies a data dictionary for archiving traffic data, including conventional traffic monitoring data, data collected directly from ITS systems, and travel time data from probe vehicles.
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From page 167... ...
165 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Standard Author Organization and Location Summarya Standard for Message Sets for Vehicle/Roadside Communications IEEE Available for purchase from IEEE website Standard messages for commercial vehicle, electronic toll, and traffic management applications. ISP-Vehicle Location Referencing Standard SAE Available for purchase from SAE website For the communication of spatial data references between central sites and mobile vehicles on roads.
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From page 168... ...
166 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TABLE A.22. APPLICABLE ITS MARKET PACKAGES Market Package Description Applicability to Travel Time Reliability Network Surveillance Includes traffic detectors and other surveillance equipment that transmit data back to the traffic management subsystem through fixed-point to fixedpoint communications.
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From page 169... ...
167 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY 2.3.5.2.1 Need to Share Node State 2.3.5.2.2 Need to Share Link State 2.3.5.2.3 Need to Share Route State 2.3.5.3 Need to Share Link Data 2.3.5.4 Need to Share Route Data Section 2.3.6: Need to Provide Control of Devices 2.3.6.1 Need to Share Detector Inventory 2.3.6.1.2 Need Updated Detector Inventory 2.3.6.1.3 Need to Share Detector Status 2.3.6.1.4 Need for Detector Metadata 2.3.6.1.5 Need for Detector Data Correlation 2.3.6.1.6 Need for Detector Data Sharing 2.3.6.1.7 Need for Detector History 2.3.6.5 Need to Share Environment Sensor Station (ESS) Data 2.3.6.5.1 Need to Share ESS Inventory 2.3.6.5.2 Need to Share Updated ESS Inventory 2.3.6.5.3 Need to Share ESS Device Status 2.3.6.5.4 Need to Share ESS Environmental Observations 2.3.6.5.5 Need to Share ESS Environmental Observation Metadata 2.3.6.5.6 Need to Receive a Qualified ESS Report 2.3.6.5.7 Need to Share ESS Organizational Metadata 2.3.6.6 Need to Share Lane Closure Gate Control 2.3.6.6.1 Need to Share Gate Inventory 2.3.6.6.2 Need to Share Updated Gate Inventory 2.3.6.6.3 Need to Share Gate Status 2.3.6.6.7 Need to Share Gate Control Schedule 2.3.6.8 Need to Share Lane Control and Status 2.3.6.8.1 Need to Share Controllable Lanes Inventory 2.3.6.8.7 Need to Share Controllable Lanes Schedule 2.3.6.9 Need to Share Ramp Meter Status and Control 2.3.6.9.1 Need to Share Ramp Meter Inventory 2.3.6.9.2 Need to Share Updated Ramp Meter Inventory 2.3.6.9.3 Need to Share Ramp Meter Status 2.3.6.9.8 Need to Share Ramp Metering Schedule 2.3.6.9.9 Need to Share Ramp Metering Plans 2.3.6.10 Need to Share Traffic Signal Control and Status 2.3.6.10.1 Need to Share Signal System Inventory 2.3.6.10.2 Need to Share Updated Signal System Inventory 2.3.6.10.3 Need to Share Intersection Status 2.3.6.10.8 Need to Share Controller Timing Patterns 2.3.6.10.9 Need to Filter Controller Timing Patterns 2.3.6.10.10 Need to Share Controller Schedule 2.3.6.10.11 Need to Share Turning Movement and Intersection Data
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From page 170... ...
168 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Section 2.3.7: Need to Share Data for Archiving 2.3.7.1 Need for Traffic Monitoring Data Volume 1: Requirements Section 3.3.4: Events Information Sharing 3.3.4.3 Subscribe to Event Information 3.3.4.4 Contents of Event Information Request 3.3.4.6 Required Event Information Content 3.3.4.7 Optional Event Information Content 3.3.4.8 Action Logs 3.3.4.9 Event Index Section 3.3.5: Provide Roadway Network Data 3.3.5.1 Share Traffic Network Information 3.3.5.2 Share Node Information 3.3.5.3 Share Link Information 3.3.5.4 Share Route Information Section 3.3.6: Provide Device Inventory, Status, and Control 3.3.6.1 Generic Devices 3.3.6.2 Traffic Detectors 3.3.6.6 Environment Sensors 3.3.6.7 Lane Closure Gates 3.3.6.9 Lane Control Signals 3.3.6.10 Ramp Meter 3.3.6.11 Traffic Signal Controllers Section 3.3.7: Share Archive Data 3.3.7.1 Share Traffic Monitoring Data for Data Archiving 3.3.7.2 Share Processing Documentation Metadata Volume 2: Design Content Section 3.0 TMDD ISO 14817 ASN.1 and XML Data Concept Definitions Section 3.1: Dialogs 3.1.1 Archived Data Class Dialogs 3.1.3 Connection Management Class Dialogs 3.1.4 Detector Class Dialogs 3.1.5 Device Class Dialogs 3.1.7 Environmental Sensor Station (ESS) Class Dialogs 3.1.8 Event Class Dialogs 3.1.9 Gate Class Dialogs 3.1.11 Intersection Signal Class Dialogs 3.1.12 Lane Control Status (LCS)
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From page 171... ...
169 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY 3.1.14 Node Class Dialogs 3.1.16 Ramp Meter Class Dialogs 3.1.17 Route Class Dialogs 3.1.18 Section Class Dialogs 3.1.19 Transportation Network Class Dialogs Section 3.2: Messages 3.2.1 Archived Data Class Messages 3.2.3 Connection Management Class Messages 3.2.4 Detector Class Messages 3.2.5 Device Class Messages 3.2.7 ESS Class Messages 3.2.8 Event Class Messages 3.2.9 Gate Class Messages 3.2.11 Intersection Signal Class Messages 3.2.12 LCS Class Messages 3.2.13 Link Class Messages 3.2.14 Node Class Messages 3.2.16 Ramp Meter Class Messages 3.2.17 Route Class Messages 3.2.18 Section Class Messages 3.2.19 Transportation Network Class Messages Section 3.3: Data Frames 3.3.1 Archived Data Class Data Frames 3.3.3 Connection Management Class Data Frames 3.3.4 Detector Class Data Frames 3.3.5 Device Class Data Frames 3.3.7 ESS Class Data Frames 3.3.8 Event Class Data Frames 3.3.9 Gate Class Data Frames 3.3.11 Intersection Signal Class Data Frames 3.3.12 LCS Class Data Frames 3.3.13 Link Class Data Frames 3.3.14 Node Class Data Frames 3.3.16 Ramp Meter Class Data Frames 3.3.17 Route Class Data Frames 3.3.18 Section Class Data Frames 3.3.19 Transportation Network Class Data Frames Section 3.4: Data Elements 3.4.1 Archived Data Class Data Elements 3.4.3 Connection Management Class Data Elements 3.4.4 Detector Class Data Elements 3.4.5 Device Class Data Elements
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From page 172... ...
170 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY 3.4.7 ESS Class Data Elements 3.4.8 Event Class Data Elements 3.4.9 Gate Class Data Elements 3.4.11 Intersection Signal Class Data Elements 3.4.12 LCS Class Data Elements 3.4.13 Link Class Data Elements 3.4.14 Node Class Data Elements 3.4.16 Ramp Meter Class Data Elements 3.4.17 Route Class Data Elements 3.4.18 Section Class Data Elements 3.4.19 Transportation Network Class Data Elements Section 3.5: Object Classes 3.5.1 Archived Data 3.5.3 Connection Management 3.5.4 Detector 3.5.5 Device 3.5.7 ESS 3.5.8 Event 3.5.9 External Center 3.5.10 Gate 3.5.13 Intersection Signal 3.5.14 LCS 3.5.15 Link 3.5.16 Node 3.5.19 Ramp Meter 3.5.20 Route 3.5.21 Section 3.5.22 Transportation Network APPLICABLE SECTIONS OF DATA DICTIONARY FOR ADVANCED TRAVELER INFORMATION SYSTEMS 6.43 Information request, linkTravelTime 6.99 Estimate of travel time returned to the traveler based upon route 6.100 Estimate of travel time between way points or from–to origin–destination and way point DETECTOR DIAGNOSTIC ALGORITHM The most pervasive data quality problem inherent to infrastructure sensors is malfunctioning equipment. For example, on an average day in California, only about 70% of the freeway loop detectors statewide are transmitting good data; the remaining 30% are either transmitting bad data or no data.
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From page 173... ...
171 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY component must recognize when reported speed, occupancy, or flow values are inaccurate so that they can be imputed. In the wider academic literature, algorithms have been developed to determine when detectors are bad so that processing can remove the data that they report.
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From page 175... ...
173 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY The exact algorithms employed for monitoring detector health in a reliability monitoring system will depend on the location and facility type being monitored. For example, rural routes may have lower traffic volumes, and thus require a higher threshold of zero-flow samples for a detector to be considered bad.
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From page 176... ...
174 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY PEMS CALCULATIONS PeMS Speed Calculation PeMS uses a g-factor, which represents the effective length of a vehicle, to calculate speed from flow and occupancy detector outputs. The g-factor is a combination of the average length of the vehicles in the traffic stream and the tuning of the loop detector.
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From page 178... ...
176 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY 3. Compute delay due to bottlenecks, Dbn -- Take the recurrent bottleneck locations that are active more than 20% of the days in the quarter.
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From page 179... ...
177 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Travel Time Predictions PeMS graphically displays a prediction of the travel time for a selected route from the time selected through the rest of the day. The travel time prediction is done by examining the collection of historical travel times for the route and choosing the days with the three closest travel time profiles.
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From page 180... ...
178 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY TranStar: Houston, Texas Summary TranStar filters AVI travel time estimates by defining a set of valid recorded travel times during each 30-second evaluation period based on those that are within 20% of the estimated travel times between the same two points for the previous 30-second time period. Algorithm TranStar's algorithm was also developed by the Southwest Research Institute and is the same as that used by TransGuide, but travel times are updated each time new travel time information is obtained from a vehicle instead of being updated at fixed intervals.
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From page 181... ...
179 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Dion and Rakha Algorithm An AVI filtering algorithm was developed by Dion and Rakha to provide travel time estimates in areas where there is low market penetration of AVI sensors (2)
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