Interface - The Journal of Wheel/Rail Interaction

RAIL CANT

Rail Cant Measurement of Concrete Crossties (continued)

ATIP Rail Cant Exceptions
The RPMS onboard the FRA’s Automated Track Inspection Program (ATIP) geometry cars uses a laser- / camera-based imaging equipment to measure left and right rail profiles, and is capable of reporting exceptions (POS<>NEG) in locations where cant exceeds a user-defined threshold. Starting with the measured rail profile and reference templates, the RPMS determines several parameters including rail section, rail cant, rail headwear loss, and the amount of rail overflow (lip). The RPMS onboard the ATIP cars is fully integrated with the Track Geometry Measurement System, Ride Quality, and other onboard electronic measurement systems. Because of this, detected rail cant exceptions are tagged with GPS location information and are included in the Track Geometry Inspection Report and are consistent with other onboard measurements exception types.

On the FRA geometry cars, there are two tiers of thresholds, referred to as “alerts” and “alarms,” which are used to identify “excessive” cant values. These levels are illustrated in Figure 4, where the yellow regions represent alerts and the red regions represent alarms. The thresholds are easily changed onboard the geometry car to adapt to crossties that orient the rail with different cants, i.e., 1:30 or 1:20 ratios. Table 1 shows the threshold values characteristically used during testing on the FRA ATIP cars and reported as advisories. Proper remedial action of the advisories identified through automated inspection relies on re-inspection in the field.

Ongoing Work
The Railroad Safety Advisory Committee, Track Safety Standards under task number 07-01 (concrete crosstie task force) has held several meetings since November 2007 to consider improvements relating to fastening rail to concrete crosstie. The work is ongoing with the following mission statement: The Task Force will consider all available scientific and empirical data or direct new studies to evaluate the concrete crosstie rail seat deterioration phenomenon and through consensus propose best practice, inspection criteria, or standards to assure concrete crosstie safety. The Task Force will develop definitions and terminology as required and disseminate pertinent information to detect through visual or mechanical inspection any safety concerns. The task force intends to issue a specific report recommendation to the committee in the near future.

Existing Regulatory Requirements
Crosstie regulations are contained in 49 CFR Part 213, Subpart D §213.109, which states in part:

(a)

Crossties shall be made of a material to which rail can be securely fastened

(b)

Each 39-foot segment of track shall have:

(c)

A sufficient number of crossties which in combination provide effective support that will,

Hold gauge within the limits prescribed in §213.53(b)

ii.

Maintain surface within the limits prescribed in §213.63 and

iii.

Maintain alignment within the limits prescribed in §213.55

(2)

The minimum number and type of crossties specified in paragraphs (c) and (d) of this section effectively distributed to support the entire segment; and

(3)

At least one crosstie of the type specified in paragraphs (c) and (d) of this section that is located at a joint location as specified in paragraph (f) of this section.

(d)

Each 39-foot segment of: Class 1 track shall have five crossties; Classes 2 and 3 track shall have eight crossties; and Classes 4 and 5 track shall have 12 crossties, which are not:

(1)

Broken through,

(2)

Split or otherwise impaired to the extent the crossties will allow the ballast to work through, or will not hold spikes or rail fasteners,

(3)

So deteriorated that the tie plate or base of rail can move laterally more than 1/2 inch relative to the crossties; or

(4)

Cut by the tie plate through more than 40 percent of a ties’ thickness.

Crosstie regulations are also contained in the High-Speed track safety standards under 49 CFR Part 213 Subpart G §213.335 (d) 1-7, which state in part:

(a)

Crossties shall be made of a material to which rail can be securely fastened,

(b)

Each 39 foot segment of track shall have,

(1)

A sufficient number of crossties which in combination provide effective support that will,

hold gauge within the limits prescribed in §213.323(b)

ii.

Maintain surface within the limits prescribed in §213.331; and

iii.

Maintain alignment within the limits prescribed in §213.327

(c)

For non-concrete tie construction, each 39 foot segment of Class 6 track shall have fourteen crossties; Classes 7, 8 and 9 shall have 18 crossties which are not-

(1)

Broken through,

(2)

Split or otherwise impaired to the extent the crossties will allow the ballast to work through, or will not hold spikes or rail fasteners,

(3)

So deteriorated that the tie plate or base of rail can move laterally 3/8 inch relative to the crossties,

(4)

Cut by the tie plate through more than 40 percent of a crosstie’s thickness,

(5)

Configured with less than 2 rail holding spikes or fasteners per tie plate, or

(6)

So unable, due to insufficient fastener toeload, to maintain longitudinal restraint and maintain rail hold down and gauge.

(d)

For concrete tie construction, each 39 foot segment of Class 6 track shall have fourteen crossties, Classes 7, 8 and 9 shall have 16 crossties which are not-

(1)

So deteriorated that the prestress strands are ineffective or withdrawn into the tie at one end and the tie exhibits structural cracks in the rail seat or in the gauge of track,

(2)

Configured with less than 2 fasteners on the same rail,

(3)

So deteriorated in the vicinity of the rail fastener such that the fastener assembly may pull out or move laterally more than 3/8 inch relative to the crosstie,

(4)

So deteriorated that the fastener base plate or base of rail can move laterally more than 3/8 inch relative to the crossties,

(5)

So deteriorated that rail seat abrasion is sufficiently deep so as to cause loss of rail fastener toeload,

(6)

Completely broken through; or

(7)

So unable, due to insufficient fastener toeload, to maintain longitudinal restraint and maintain rail hold down and gauge.

Acknowledgements
Special thanks to Kevin Kesler, Susan Cook, Eric Sherrock, and Gary Martin of ENSCO, Inc., and to the men and women onboard the ATIP cars for their everyday contributions to rail safety. Further information about FRA automated track inspection technology is accessible at http://atip.fra.dot.gov/ or the FRA home page at http://www.fra.dot.gov/.

Arthur Clouse is Manager, Automated Track Inspection Program, Track and Structures Division, Federal Railroad Administration Office of Safety.

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