Optimizing the Check Gauge of Restraining Guard Rail
RESEARCH PROBLEM STATEMENT
Restraining guard rail (hereinafter RestRail) is commonly used in the track structure of North American rail transit systems.RestRail systems consist of a rail installed along the inside of the inner running rail (low rail) of horizontal curves, including the curved leads of turnouts.The flangeway opening between the low rail and RestRail is typically in the range of 1.50-in. (38mm) to 2.12-in. (54mm), depending on the wheel flange nominal width.The back of the wheel flange of the lead axle in a truckset bears against the gage face of the RestRail to provide some or all of the steering guidance to the wheelset, and thereby to the truckset and vehicle.RestRail is installed on many rail transit properties because it is either stipulated in the Agencys track standards or recommended by their consultants, in the expectation that the RestRail will provide the following benefits:
Increase the safety of operation by preventing flange-climb derailments, especially when the wheels have small and/or worn flanges
Prolong the service life of the outer, high rail by decreasing rail wear, especially on the gauge face
Reduce the noise associated with wheelsets negotiating curves
Assuming that the RestRail actually provides these benefits and therefore justifies its cost of installation and maintenance, the most important question is: what is the correct check gauge that should be used to obtain optimum performance?Check gauge is the dimension between the gauge face (point) of the high rail opposite the RestRail installation and the gauge face (point) of the RestRail itself, where the flange backside contacts the face of the RestRail.This dimension will determine whether the flange of the wheel on the high rail makes contact with the gauge face of the rail, or never makes contact.
This dimension is crucial in determining whether the RestRail performs its function in an optimum manner and delivers the anticipated benefits.In North America, almost uniformly among Agencies but with a few exceptions, track designers and Agency track standards call for shared contact, on the basis that the high rail and RestRail will share the curving forces and associated wear more or less equally, and the check gauge and track gauge is set to allow this sharing.It is hoped that the high rail and RestRail will wear out and be replaced during the same maintenance track outage.
Conversely, in Europe the normal practice is to increase the check gauge dimension and track gauge so that no flange contact with the high rail will occur under any combination of wear and tolerances, so that the RestRail resists all the curving forces and therefore experiences all the gauge-face wear; the high rail sees only top wear.This is accomplished by simply widening track gauge.Why do the Europeans do this?According to several operating transit Properties in both Germany and France, their reasoning is:
that because of the variations in the wheel mounting back-to-back dimensions, wheel flange wear, rail gauge face wear, and track gauge variations, it is impossible to have shared contact with both the high rail and RestRail in any reliable manner
that when contact is shared intermittently, adverse steering forces are introduced into the trucks, resulting in rapid oscillation and in significantly increased nosing forces possibly damaging the track, such as gouging wear of both the high rail and RestRail, and breaking the bolts holding the RestRail
that the sudden, adverse steering forces likely result in a lurching, uncomfortable ride in the vehicles, especially affecting standees
contacting the back of the flange on only the RestRail reduces curving noise, as only one rail and one wheel is involved, as opposed to two, which results in less bell-ringing and wheel squeal
that it significantly reduces wear on the high rail, so that it has a considerably extended life, roughly equal to the low rail
that by using a purpose-designed RestRail rolled section, such as UIC-33 in the U-69 support arrangement, adjustment for RestRail wear to maintain check gauge within specified tolerances is done fairly easily, and that provision fora raised guard RestRail is readily accommodated
that their lubrication or friction control can be concentrated on the RestRail, simplifying the installation of lube or friction control applicator appliances
The obvious question is: are the North Americans or Europeans doing it the right way?It is an important question, as if the Europeans are right, then we here in North America are perhaps using a practice that is not only less than optimal but may also lead to operating safety issues, premature wear or damage to the track that increases the maintenance requirements, makes for an uncomfortable ride, and may also result in additional noise and vibration generation.
The existing literature is not much help, here.The American Railway Engineering and Maintenance of Way Association (AREMA) Manual of Recommended Practice and other published design guidelines address none of the issues noted above.The AREMA Manual, for instance, does not list Restraining Rail as a topic in any chapter.TCRP Report # 57 states in Chapter 4 that the owning Agencies vary widely in their design criteria, but offers no guidance regarding proper installation criteria.Most of the track standards developed and used on various properties are based simply on prior practice without independent verification that the practice is appropriate or effective.Therefore, there is a significant lack of knowledge about this issue that has serious implications in operating safety, passenger comfort, and maintenance requirements.
From a transit planning perspective, knowing the optimum RestRail check gauge measurement may significantly reduce potential noise and vibration issues.This in-turn may result in lower capital costs due to the need for fewer sound walls, floating slabs and other remediation techniques.From a larger noise and vibration perspective, knowing the optimum check gauge could simplify design alignments for new construction, particularly in urban / suburban locations.
The objective of this RestRail check gauge research is to provide reliable data regarding the effect on safety of operation, passenger comfort, noise and vibration generation, and maintenance requirements resulting from the use of the shared contact philosophy generally used in North America versus the RestRail only contact used on many Properties in Europe and a few in North America.
The research objective can be accomplished through the following phases:
1. A literature search of prior research work or currently under way, especially private studies carried out in North America and in Europe, which could be pertinent, and can possibly be incorporated into this research.
2. A study of present practices on a significant number of operating properties, both North American and European, stressing those that operate similar vehicles on similar tracks, comparing their check gauge practices, and evaluating derailments, rail wear, wheel wear and wheel truing practices,costs of maintenance, and curving noise.
3. Computer modeling to determine if there are substantive theoretical differences in the performance of the two different check gauge philosophies and practices.
4. Publication of Phase 1 Report.
Phase 2 - If the results in Phase 1 indicate that there are potential operating benefits in the European practice vs current North American practice, then Phase 2 will be implemented
5. Develop optimum recommended plans for check & track gauge, and lubrication/friction control for typical applications on both heavy rail, light rail, and streetcar.
6. Perform vehicle and track verification under controlled conditions, with specific vehicles, wheel forms and trucks/suspensions.This will probably best be performed using the facilities and equipment of at least two (2), preferably three (3), cooperating transit Agencies: one heavy rail, one light rail, and, optionally, one streetcar, if funding permits.A test curve or curves modified to prevent high rail flange contact would be paired with a matching curve(s) using current practice.Both would be instrumented and measured, and the vehicle dynamic responses, noise and vibration measured periodically, and track reaction forces and wear measured over a significant length of time, probably at least six (6) months, possibly up to a one (1) year, to allow a useful comparison.
7. Publish the Phase 2 Report, comparing the track reaction results and rail wear, noise and vibration generation, and vehicle dynamic responses from the test curves in a comprehensive document.
Phase 3 - If the verification test results in Phase 2 are positive, then Phase 3 will be implemented, predicated on additional transit Agencies volunteering to do the testing primarily at their expense
8. If the benefits are substantial on an improved performance and cost/benefit basis, then have other Agencies volunteer to perform similar tests, but perhaps without full-depth instrumentation needed; mainly to assure compatibility compare ride comfort, rail wear, and noise.
9. Publish the Phase 3 Report, and provide all the research results to an organization empowered to draft the information into a form suitable for inclusion in a Manual of best & recommended practices used universally by the rail transit industry,
ESTIMATE OF THE PROBLEM FUNDING AND RESEARCH PERIOD
Recommended Funding:The research is envisioned as being in three (3) Phases so that positive results in a Phase will result in activating further research in the next Phase; negative results will result in research termination at the end of the Phase in question.The Phases, as listed above, are estimated to require the time and funding as listed below:
Phase 1 is estimated to require funding in the $35,000 to $45,000 range.It is anticipated that the literature search, Agency practices profiling and computer modeling can be done simultaneously.
Phase 2 will require funding in the $115,000 to $140, 000 range, based on the facilities and vehicles being Agency furnished, operated and maintained at no cost to TCRP.The research effort will require the installation and monitoring of the instrumentation required, but will not require a full-time presence at the test sites.
Phase 3 is estimated to require funding in the $45,000 to $75,000 range, depending on how many Agencies volunteer for the test program, and how closely the researchers monitor their progress.
Total Funding Required:
Based on the premise that the research is promising and that all three Phases are implemented, the total funding requirement will be in the $195,000 to $260,000 range.
Research Period:In each Phase listed, time is allowed for drafting the Final Report.
We estimate that the Phase 1 literature search, profiling of current practices and computer modeling will take four (4) to six (6) months.The Phase 2 field testing and verification will take from eight (8) months to 15 (15) months; however, a full-time researchers presence is not required.The researcher(s) will make periodic visits to monitor the instrumentation and make wear and noise/vibration measurements, probably at about two (2) month intervals after installation of the test.Phase 3 will probably extend over at least one (1) year, perhaps more, depending on the number of volunteer Agencies, and how extensive research support is required for their testing.The most feasible arrangement would be for the research team to instruct Agency maintenance personnel in the proper way to monitor wear, noise and vehicle responses, with instrumentation belonging to the Agency.The researchers would help the Agency personnel to draft their Final Report, which would be published by the Agency, not TCRP.
The total Research Period is estimated to extend over approximately 2 years.
URGENCY AND PAYOFF POTENTIAL
The urgency of the proposed RestRail research program is driven by four (4) considerations:
1. the potential safety issues involved; as we dont presently know the effectiveness of RestRail as it is presently applied
2. the ride quality and possible passenger injury associated with sudden lateral accelerations caused by extraordinary steering forces applied during curving
3. the possible reduction in noise and vibration generation
4. the possible reduction in rail wear, especially caused by nosing, and track damage, such as broken RestRail bolts, leading to reduced life-cycle costs and maintenance requirements
No impediments to applying the results of this research are foreseen, except as it may make obsolete the materials and practices currently in use on many Agencies.On installations on concrete ties and Direct Fixation, it may not be feasible to adjust the track and check gauge.To change these type installations would have to be analyzed on a cost/benefit basis to see if it makes sense.New installations should not present any real problems to implementation.
The Transportation Test Center, Inc. at Pueblo, Colorado, is currently conducting research on frog guard rails, and under the TCRP D-7 Project, has researched some of the RestRail issues; that work is now completed and published.Also, TTCI recently completed research and prepared a report on Wheel Flange Climb Derailment Criteria which is directly applicable to this proposed research.
UMTA (now FTA) published a 2-volume report in 1981 titled, U.S. Transit Track Restraining Rail Volume 1:Study of Requirements and Practices; and Volume II: Guidelines.These documents, UMTA-MA-06-0100-81-6 and 7 are now quite dated due to advent of many newer systems, especially LRTs.