development and use-v-ti monitors for autonomous track inspection
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V/TI monitorTRANSCRIPT
Development and Use of V/TI Monitors for Autonomous Track Inspection
Authors: Larry Biess (CSX), Matthew Dick (ENSCO, Inc.)
ABSTRACT
The Vehicle/Track Interaction Monitor (V/TI) has long been a useful tool for determining locations of
excited vehicle/track interaction and aiding in track maintenance to remediate and prevent such locations.
V/TI systems typically use on-board single point thresholds to create track exceptions that are then
inspected by railroad personnel to identify and correct track conditions. This paper discusses a recent
study of mainline track caused derailment locations using repeated, low-level exceptions to look beyond
the single data point exception for opportunities to improve track safety, how the exceptions are
presented to inspectors to evaluate track conditions, including how V/TI exceptions are disseminated to
field personnel and how repair information is recorded. Additionally the paper discusses recent updates
to the system and how CSX has been able to utilize the capabilities. Included is discussion of track
profile measurement using a 10-ft mid-chord offset (MCO) and repeat analysis to evaluate clusters of V/TI
exceptions.
BACKGROUND
Vehicle/Track Interaction (V/TI) Monitors are autonomous systems that provide near real-time detection of
unsafe track conditions. The V/TI system is in the tenth year of operation in North America; currently,
there are over 235 of these systems operating on locomotives, passenger and freight cars in daily
revenue service. The system includes onboard measurement equipment as well as a central data-
management and reporting system.
The purpose of the V/TI Monitoring System is to continuously sample all sensor inputs which measure
vehicle response due to the interaction with the track. It detects inputs which exceed thresholds of
interest, and send a capture of all sensor waveforms back to a central data-management system. When
the sensor waveforms are received by the data-management system, they are cross-checked to eliminate
© 2011 AREMA ®
false-positive reports and stored in a database. The event that was just detected (called an “exception”)
can be searched as part of a database query based on location, vehicle number, date/time, and so forth.
In addition to being stored in the database, high-priority exceptions can also be forwarded to personnel in
the form of email and/or text messages. The standard V/TI product includes two axle sensors to measure
wheel/rail impacts, one truck sensor to measure lateral truck movement, and one car body sensor to
measure lateral & vertical car body movements.
APPLICATION OF TECHNOLOGY
IN 2008 CSX installed 10 V/TI systems on a variety of locomotives. Exception thresholds, prioritization,
definitions, and corrective actions were defined and internal documentation was written to explain to field
personnel the meaning of these exceptions and the required remedial actions. These systems are
currently providing the CSX Engineering Help Desk and Roadmasters with near-real time exceptions that
are created using the V/TI on-board system and single count events that exceed a threshold. Based on
the latitude and longitude and a CSX lookup table provided by CSX, exception notification is sent to the
owning Roadmaster via e-mail. The current thresholds are shown in Table 1 and an example V/TI email
notification is shown in Figure 1.
Table 1. Current CSX V/TI Single Event Exception Thresholds
Measurement Initial Department E-Mail High Medium
Wheel Impact AXV Engineering Yes >130 kips 130<x<115 kips
Car Body Vertical CBV Engineering Yes > 1.3 g 1.3<x<1.15 g
Car Body Lateral CBL Engineering Yes > 0.8 g 0.8<x<0.7 g
Truck Lateral TRL Mechanical Yes > 0.4 g > 0.4 g
© 2011 AREMA ®
Figure 1. Screen shot of V/TI E-Mail Notification
In 2011, the Integrated Track Inspection Team (ITIS) is working to integrate these exceptions directly into
the Track Inspector Laptop application as navigable exceptions, similar to how they respond to geometry
exceptions from the Track Geometry Car and Geometry Measurement System cars. This integration will
make it easier for the inspectors to find and manage exceptions, and for management to monitor
exception remedial actions taken, and whether or not exceptions recur following a repair. The V/TI
integration work will serve as a platform for future track-health alerts using measurement technologies.
Furthermore, in 2011 systems installed on foreign locomotives operating on CSX track report to CSX in
the same manner as CSX owned systems. Likewise, if the CSX locomotive operates on a participating
railroad, they receive the data in the same manner as their own systems. This Data Sharing Program
eliminates manual forwarding of exception information between CSX and the foreign road.
Analysis:
In the first three quarters of 2010, CSX experienced approximately 53 track-caused derailments for a total
estimated cost of $22 million. CSX provided ENSCO with the location information of these derailments
and asked for a full analysis on all V/TI related data looking back a year from the date/time of the
derailment occurrence. The new analysis was targeted to determine the effective coverage of the existing
10 V/TI locomotives in order to suggest an additional number of units for deployment and to perform cost
and economic analysis required for project approval. In additional, the analysis determined whether or not
© 2011 AREMA ®
using historical low-threshold exceptions might be useful for identifying high-risk track conditions not
diagnosed using current track inspection and testing methods.
The V/TI exceptions used by CSX identify locations using a “single hit” or on-board threshold that triggers
an on-board modem to call and deposit the alert occurrence in a database that is used to deliver e-mails
to Roadmasters for follow-up. Additionally the alert occurrence is recorded in TCIS and the TCIS incidents
are closed by the Roadmaster or Roadmaster designee. These exceptions are valuable and have allowed
CSX to identify crushed heads, low joints/joint batter, broken heal blocks, broken switch points, and other
track conditions that cause high lateral and vertical accelerations. The analysis that followed this request
showed that CSX’s track coverage using the existing 10 systems was limited primarily to five
subdivisions, with the remaining subdivisions having little coverage by the units.
While examining the subdivisions with adequate data for analysis, five derailment locations were
identified. An interesting discovery from the derailment data analysis was that “clusters” of low-level V/TI
exceptions occurred at the point-of-derailment prior to the derailment. A list of the investigated
derailments is shown in Table 2. Figure 2 depicts the cluster observed at Subdivision E.
Table 2. Investigated Track Cause Derailments Subdivision Cause
Subdivision A Broken rail - Head and web separation (outside joint bar limits)
Subdivision B Switch point gapped (between switch point and stock rail)
Subdivision C Defective spikes or missing spikes or other rail fasteners
Subdivision D Track alignment irregular (buckled/sun kink)
Subdivision E Broken rail - Transverse/compound fissure
© 2011 AREMA ®
Figure 2. Screen shot of Subdivision E showing V/TI activity leading up to a broken rail derailment.
The results of this study reveal that cluster exceptions can provide insight into conditions not identified by
the standard single threshold exceptions. Of particular interest, based on the cause codes, is the potential
to prevent derailments using V/TI cluster alerts that go beyond alignment and profile issues.
Indeed, in one instance CSX identified a V/TI location with an escalating measurement for carbody
vertical acceleration that we believe contributed or caused the failure of a truck bolster that resulted in a
derailment. In this instance, the Roadmaster responded by inspecting the track and identifying a profile
that is less than that prescribed by CFR 213.63 for the class of track. Since this measurement did not
exceed CSX or FRA values for profile, the track was determined to be safe for the passage or trains and
no action was taken. Unfortunately, 48 hours after this assessment a tank car derailed from a broken
bolster. A photograph of the bolster is shown in Figure 3.
© 2011 AREMA ®
Figure 3. Failed truck bolster.
Based on this insight, the types, counts, and severities of these events were then tabulated to create a
“rule” to develop an alert threshold that can automatically identify other locations that have similar
clusters.
Outcome of Analysis
As a result of the analysis 15 new units are in the process of being added to the fleet in 2011.
Additionally CSX entered into the data sharing agreement to increase V/TI coverage of the network.
Results of the derailment analysis aid in the development of “cluster exceptions” which is discussed
further below. Finally, additional work to integrate V/TI system health alerts in the CSX Locomotive
Power Management System is underway. Learning from the new data and occurrences, and based on
existing derailments, CSX believes that a 10% reduction in track-caused derailments on main and siding
tracks is achievable with V/TI.
TECHNOLOGY ADVANCEMENTS
V/TI Exceptions in ITIS
The Integrated Track Inspection System (ITIS) is a laptop application solution developed by CSX for
conducting paperless track inspections. A screen shot of the application is shown in Figure 4. It allows
the inspector to plan and conduct track and point asset inspections digitally. Additionally, it provides the
Bolster fractured from an overstress event; no evidence
of pre-existing fatigue.
© 2011 AREMA ®
inspector pertinent information about the asset during the inspection such as track geometry car
exceptions. These exceptions are posted in the application with their relevant information such that the
inspector can conduct an inspection of the exception location. This process is currently being developed
to include V/TI exceptions in the same manner. The unique aspect of integrating the V/TI exceptions is
that the exception data is automatically delivered to the ITIS application such that no manual loading or
processing is required. In this arrangement, exceptions are delivered into the ITIS application relatively
quickly (in a manner of minutes) after they have been detected. With the ease of use of ITIS and the up-
to-date V/TI exception data posted in the application, it is expected to achieve a higher utilization of risk
track conditions inspection and remediation.
Figure 4. Screen shot of the Integrated Track Inspection System (ITIS).
Cluster Analysis
As discussed earlier, derailment investigations were performed to determine what V/TI exceptions (if any)
occurred at the point-of-derailment prior to the derailment. An example cluster is shown in Figure 5. A
© 2011 AREMA ®
pattern was observed in the results which was repeated low-level exceptions of multiple V/TI exception
types at a discrete location on the track which is deemed a “combo cluster”. During the analysis it was
quickly observed that due to relatively low V/TI traffic that the basic combo cluster characteristics were
observed, but not well defined. Additional derailment investigation work was performed on another
railroad with greater V/TI traffic (50+ units in the fleet), where the cluster definition was greater. An
example of this is shown in Figure 6. Additionally the other railroad had V/TI Monitors equipped with the
Mid-Chord Offset (MCO) functionality which is discussed in more detail later in this paper.
At first glance it was difficult to understand how low-level exceptions could be contributing to a track
caused derailment. With further examination and observation these locations shared a commonality of
repeated exceptions and multiple types of exceptions in the cluster (axle impact exceptions + car body
vertical exceptions or axle impact exceptions + MCO exceptions). Additionally the differences between
higher and lower severity exceptions were reviewed. When a V/TI Monitor detects an “Urgent” or “High”
severity exception, an inspector quickly reviews the location and typically finds a specific condition that
needs remediation (i.e. broken joint bar or fouled ballast). Typically these conditions are repaired soon so
that a derailment is prevented. In comparison, the V/TI detects “Priority” or “Low” severity exceptions that
typically don’t get individually inspected, but rather put into more macroscopic track maintenance
planning. These low level exceptions begin to repeat at a single location when wheel/rail impacting,
elevated rail stress from increased dynamic wheel load, and defection from fouled ballast are present.
This activity begins to accumulate such that it begins to create an environment for fatigue and longer term
deterioration, causing a catastrophic failure such as broken rail, broken joint, bolt hole breaks, sub grade
failure, etc…
© 2011 AREMA ®
Figure 5. Example combo cluster exception found during derailment investigation.
Figure 6. Example combo cluster exception with MCO exceptions Found at the point-of-derailment (POD).
Using the cluster patterns observed during the derailment investigations, an algorithm was created to
recognize locations that were deemed “combo clusters”. This was accomplished by implementing a
server-side algorithm that first identifies locations of clusters based on a maximum radius in feet that the
Car body Exception
Axle Exception
Axle Exception
Car body Exception
MCO Exception
© 2011 AREMA ®
cluster can occupy. Then the clusters are evaluated for their severity, which includes average train
speed, types of exceptions, and number of repeat exceptions. Each “combo cluster” is given a severity
level similar to single-exception thresholds, which are from highest to lowest, “Urgent”, “Near Urgent”,
“Priority”. A second layer of severity assignment is added for promotion and demotion of exceptions - the
purpose being to highlight suspect locations, while downplaying stable locations. This is accomplished
using the following three methods:
1. If a cluster has occurred where no cluster has occurred before, it is promoted to a higher severity.
2. If a cluster is deteriorating over time, it is promoted to a higher severity.
3. If a cluster has shown stable characteristics for a sufficient time, it is demoted to a lower severity.
After receiving its final severity level, the combo cluster is then treated like a regular V/TI exception where
Urgent and Near Urgent clusters are emailed, text message notified to field personnel for inspection.
It is anticipated that the algorithm that ranks the severity of the clusters will evolve as more information is
analyzed in order to sharpen the prediction of derailment. Until that time, it will continue to detect
noteworthy locations such as deteriorating insulated joints, field welds, and frogs.
Mid-Chord Offset
A new functionality developed is the use of the V/TI Monitor axle accelerometers to measure 10-ft mid-
chord offset of track profile irregularities. A 10 foot chord length was chosen to focus on short-chord track
profile irregularities which are typically associated with mud spots or pumping joints. Example MCO
signatures and corresponding track conditions is shown in Figure 7 and Figure 8. What is interesting with
short-chord irregularities is that they typically induce higher stress to the rail than long-chord irregularities
(62 ft chord length) because the rail is bent more aggressively. Additionally short-chord irregularities can
generate faster than long-chord because less material is affected. Because of the elevated rail/joint
failure risk and rapid deterioration associated with short-chord irregularities, the V/TI Monitor was a good
platform for measurement. The V/TI allowed for significant coverage and traffic to identify rapid changes
© 2011 AREMA ®
in short-chord conditions. Additionally, the V/Ties installed on locomotives are capable of measuring the
track “loaded”.
Figure 7. Example 10-ft Mid-Chord Offset signature of a mud spot.
Figure 8. Corresponding mud spot to the signature shown in Figure 7.
An interesting outcome of utilizing the V/TI Monitor for a mid-chord measurement has been the threshold
determination. It was quickly realized that the MCO exceptions required a “class-of-track” system of
thresholds, similar to 62-ft track profile thresholds. However, with an autonomous system, it is more
challenging to determine the appropriate class of track as compared to a manned track geometry car. In
order to apply class-of-track thresholds to the V/TI MCO measurements duel system server-side
© 2011 AREMA ®
architecture was implemented which allows either vehicle speed based, or geo-fence based class-of-track
thresholds. The speed based system uses GPS measured speed of the vehicle at the time of the
exception, to determine the class of the track. This has obvious limitations when the vehicle is traveling
slower than the maximum posted speed. However, it is considered a simple approach that can be
implemented quickly to produce conservative results. The second method is to define the different track
class locations with geo-fences, which are GPS based fences that put bounds on the various different
class locations. When an exception’s GPS occur with the geo-fence, it uses the respective class’
thresholds. This method too has limitations as the standard GPS antenna and base map are not
currently accurate enough to determine the track in multiple track territory. Overall, with the two methods,
a workable and conservative class-based threshold system is employed. It is anticipated with the
upcoming release of PTC grade base map data, that the geo-fence approach will quickly become the
preferred approach.
Further work is now underway to investigate the differences of short-chord risk with wood and concrete tie
track. Additionally, a MCO cluster exception is currently being investigated such to identify short-chord
degradation.
CONCLUSIONS
In summary, the V/TI Monitor system has been found to be a useful track measurement system which
helps to prevent derailments by providing continuous autonomous monitoring of the track condition.
Utilizing a fleet of the monitors allows CSX to have greater assurance that the track condition is
understood in a near real-time fashion. Additionally, providing the information to ITIS allows for greater
efficiency of inspection and repair. Finally, new measurements and data analysis techniques are
expected to make further cuts in derailment risk.
© 2011 AREMA ®
ACKNOWLAGEMENTS
The authors would like to thank the other railroads and agencies which have participated in the V/TI Data
Sharing, Cluster Exceptions, and Mid-Chord Offset development. Those include Union Pacific, BNSF,
Norfolk Southern, Canadian Pacific, and the FRA Office of Safety.
LIST OF TABLES
Table 1. Current CSX V/TI Single Event Exception Thresholds
Table 2. Investigated Track Cause Derailments
LIST OF FIGURES
Figure 1. Screen shot of V/TI E-Mail Notification
Figure 2. Screen shot of Subdivision E showing V/TI activity leading up to a broken rail derailment.
Figure 3. Failed truck bolster
Figure 4. Screen shot of the Integrated Track Inspection System (ITIS).
Figure 5. Example combo cluster exception found during derailment investigation.
Figure 6. Example combo cluster exception with MCO exceptions
Figure 7. Example 10-ft Mid-Chord Offset signature of a mud spot.
Figure 8. Corresponding mud spot to the signature shown in Figure 7.
© 2011 AREMA ®
2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
Larry BiessDirector Advanced EngineeringCSX
Matthew Dick, PEStaff Technical ManagerENSCO, Inc.
2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
• Vehicle Track Interaction Monitors (V/TI) are autonomoustrack inspection systems that utilizes acceleration measurements mounted on a vehicle with real-timereporting.
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Over 14 years of operation with currently 239 V/TI units inspecting approximately 40,000 miles per day in North America and Australia.
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AntennaMain UnitCarbody SensorTruck SensorAxle Sensors
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
In 2008 CSX installed 10 V/TI systems.
CSX developed internal documentation to explain the V/TI data and the required remedial actions.
These systems are currently providing the CSX Engineering Help Desk and Roadmasters with near-real time exceptions.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
In the first three quarters of 2010, CSX experienced approximately 53 track-caused derailments for a total estimated cost of $22 million.
CSX provided ENSCO with the location information of these derailments and asked for a full analysis on all V/TI related data.
The new analysis was targeted to determine the effective coverage of the existing 10 V/TI locomotives.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
While examining the subdivisions with adequate data for analysis, five derailment locations were identified.
interesting discovery from the derailment data analysis was that “clusters” of low-level V/TI exceptions occurred at the point-of-derailment prior to the derailment.
Subdivision Cause
Subdivision A Broken rail - Head and web separation (outside joint bar limits)
Subdivision B Switch point gapped (between switch point and stock rail)
Subdivision C Defective spikes or missing spikes or other rail fasteners
Subdivision D Track alignment irregular (buckled/sun kink)
Subdivision E Broken rail - Transverse/compound fissure7
2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
Subdivision E showing V/TI activity leading up to a broken rail derailment.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
As a result of the analysis 15 new units are in the process of being added to the fleet in 2011.
Additionally CSX entered into the data sharing agreement to increase V/TI coverage of the network.
Results of the derailment analysis aid in the development of “cluster exceptions” which is discussed further below.
Learning from the new data and occurrences, and based on existing derailments, CSX believes that a 10% reduction in track-caused derailments on main and siding tracks is achievable with V/TI.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
Data Sharing
ITIS Integration
Clusters Analysis
Mid-Chord Offset
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In 2011, CSX joined a V/TI data sharing program.
The sharing program works by automatically forwarding foreign locomotives V/TI data to CSX when they operate on CSX track.
Likewise, when CSX V/TI locomotives operate on a foreign railroad’s track, the CSX data automatically is sent to the foreign railroad.
This Data Sharing Program eliminates manual forwarding of exception information between CSX and the foreign road.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
CSX has previously developed the Integrated Track Inspection application (ITIS).
ITIS is a paperless track inspection record keeping system.
In 2011, the CSX ITIS group is working to integrate V/TI exceptions directly into the Track Inspector Laptop application.
Additionally, work is underway to automatically transfer near real-time V/TI exception data to the ITIS system.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
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Axle Exception
Car body Exception
MCO Exception
The derailment analysis indicated that there were repeated low-level V/TI exceptions of different types at the point of derailment, prior to the derailment.
These sites have been deemed “Combo Clusters”.
An automatic algorithm was developed to search for these “Combo Cluster” patterns and notify the railroad.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
The algorithm calculates severity based on number of exceptions, number of different exception types, speed, etc…
Combo cluster exceptions are then ranks and normalized within a specific territory.
This results in a few “outlier” locations which show more activity than the rest of the territory.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
The current theory to why combo clusters correspond to derailment risk is the following:
These low level exceptions begin to repeat at a single location when wheel/rail impacting, elevated rail stress from increased dynamic wheel load, and defection from fouled ballast are present.
This activity begins to accumulate such that it begins to create an environment for fatigue and longer term deterioration, causing a catastrophic failure such as broken rail, broken joint, bolt hole breaks, sub grade failure, etc…
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
Mid-Chord Offset is a measurement of track geometry that uses the mid-point measurement between two points a fixed length apart.
10-foot Mid-Chord Offset is useful to detectshort-chord track profile conditions consistent with:
fouled ballast, tie conditions, pumping joints.
2007 FRA Office of Research study to assess effectiveness of axle acceleration monitoring concluded:
Localized conditions lacking support structure (primarily at joints) and at risk of failure can go undetected with acceleration only.Axle Accelerations can be used to derive space curve and calculate MCO. 31’- 62’ MCO likely miss target conditions; 10’ chord recommended and detection added to VTI.
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Space Curve
Mid-Chord Offset
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The MCO waveforms were characteristic of a mud spot.
Slight carbodyVertical Movement accompanied the MCO exception.
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One discrete mud spot was found.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
In summary, the V/TI Monitor system has been found to be a useful track measurement system which helps to prevent derailments by providing continuous autonomous monitoring of the track condition.
Utilizing a fleet of the monitors allows CSX to have greater assurance that the track condition is understood in a near real-time fashion.
Additionally, providing the information to ITIS allows for greater efficiency of inspection and repair.
Finally, new measurements and data analysis techniques are expected to make further cuts in derailment risk.
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2011 ANNUAL CONFERENCESeptember 18-21, 2011 | Minneapolis, MN
Union Pacific Dwight ClarkTom Toth
Canadian Pacific Ron GagneMike Rooney
BNSF Corey PastaDennis Morgart
FRA Office of Safety
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