Development and Use-V-TI Monitors for Autonomous Track Inspection

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.


• Vehicle Track Interaction Monitors (V/TI) are autonomoustrack inspection systems that utilizes acceleration measurements mounted on a vehicle with real-timereporting.

2


Over 14 years of operation with currently 239 V/TI units inspecting approximately 40,000 miles per day in North America and Australia.

3


AntennaMain UnitCarbody SensorTruck SensorAxle Sensors

4


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.

5


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.

6


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


Subdivision E showing V/TI activity leading up to a broken rail derailment.

8


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.

9


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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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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13


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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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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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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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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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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Union Pacific Dwight ClarkTom Toth

Canadian Pacific Ron GagneMike Rooney

BNSF Corey PastaDennis Morgart

FRA Office of Safety

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Development and Use-V-TI Monitors for Autonomous Track Inspection

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