Guardrail Study: Reducing Wear, Reducing Replacements.

By Xinggao Shu
Created: June 1, 2012

A detailed study of restraining rail designs and maintenance practices offers guidance for transit agencies to follow in the design, construction, wheel/rail maintenance and operation of rail systems.

Illustration courtesy of TTCI.

Fig. 11: Wheel L/V Ratio, Transit Railcar 1, Level 3 Perturbations 15 mph, No Guardrail.
Fig. 11: Wheel L/V Ratio, Transit Railcar 1, Level 3 Perturbations 15 mph, No Guardrail.
Illustration courtesy of TTCI.

Fig. 10: Wheel L/V Ratio, Transit Railcar 1, Level 2 Perturbations 15 mph, No Guardrail.
Fig. 10: Wheel L/V Ratio, Transit Railcar 1, Level 2 Perturbations 15 mph, No Guardrail.
Illustration courtesy of TTCI.

Fig. 9: Wheel L/V Ratio, Transit Railcar 1, Steady-state Curving. 15 mph, No Guardrail.
Fig. 9: Wheel L/V Ratio, Transit Railcar 1, Steady-state Curving. 15 mph, No Guardrail.
Illustration courtesy of TTCI.

Fig. 8: Both philosophies resulted in a larger wear index on leading axle wheels than the case with no guardrail, with a lower wear index from Philosophy I than that from Philosophy II.
Fig. 8: Both philosophies resulted in a larger wear index on leading axle wheels than the case with no guardrail, with a lower wear index from Philosophy I than that from Philosophy II.
Illustration courtesy of TTCI.

Fig. 7: More than twice the lateral force acts on just the guardrail using Philosophy II than the lateral force acts almost equally on both rails using Philosophy I.
Fig. 7: More than twice the lateral force acts on just the guardrail using Philosophy II than the lateral force acts almost equally on both rails using Philosophy I.
Illustration courtesy of TTCI.

Fig. 6: Guardrail W/R wear, wheel flange angle 75 degrees, AOA = 20 mrad.
Fig. 6: Guardrail W/R wear, wheel flange angle 75 degrees, AOA = 20 mrad.
Illustration courtesy of TTCI.

Fig. 5: Guardrail W/R lateral forces, wheel flange angle 75 degrees, AOA = 20 mrad.
Fig. 5: Guardrail W/R lateral forces, wheel flange angle 75 degrees, AOA = 20 mrad.
Illustration courtesy of TTCI.

Fig. 4: Wheel and horizontal restraining rail geometry.
Fig. 4: Wheel and horizontal restraining rail geometry.
Illustration courtesy of TTCI.

Fig. 3: Wheel/rail contact with guardrail (Point A is the contact point on the high rail gage corner; Point B is the contact point on the high rail wheel flange root; Point C is the contact point on...
Fig. 3: Wheel/rail contact with guardrail (Point A is the contact point on the high rail gage corner; Point B is the contact point on the high rail wheel flange root; Point C is the contact point on the guardrail; Point D is the contact point on the low rail wheel flange back.)
Illustration courtesy of TTCI.

Fig. 2: The practice of Philosophy II is to increase the check gage dimension and track gage so that no flange contact with the high rail will occur under any combination of wear and tolerances.
Fig. 2: The practice of Philosophy II is to increase the check gage dimension and track gage so that no flange contact with the high rail will occur under any combination of wear and tolerances.
Illustration courtesy of TTCI.

Fig. 1: With equal rates of wear, it is expected that the high rail and the guard/girder/restraining rail will wear out at the same time and be replaced during the same track maintenance period...
Fig. 1: With equal rates of wear, it is expected that the high rail and the guard/girder/restraining rail will wear out at the same time and be replaced during the same track maintenance period, minimizing service interruptions.

For yard curves (15 mph speed limit) with the most severe track perturbations:

No guardrails are needed for Types 1 and 2 transit railcars and Type 2 light rail vehicles.
Guardrails should be installed on curves with radii less than or equal to 755 feet for the Type 1 light rail vehicle

For mainline curves:

No guardrails are needed for Types 1 and 2 transit rail cars running at 7.5 inch cant deficiency speed with Level 2 track perturbations.
No guardrails are needed for Type 1 light rail vehicles running at 7.5 inch cant deficiency speed with Level 1 track perturbations.
No guardrails are needed for Type 2 light rail vehicles running at 4.0 inch cant deficiency speed with Level 1 track perturbations.
Guardrails should be installed on curves with radii less than or equal to 500 feet for Type 1 light rail vehicles running at 4-inch cant deficiency speed with Level 2 track perturbations.
Guardrails should be installed on curves with radii greater than or equal to 955 feet for Type 2 light rail vehicles running at 4-inch cant deficiency speed with Level 2 track perturbations.

The guidelines offer guidance that transit agencies can follow in the design, construction, wheel/rail maintenance and operation of rail transit systems. Further study on guardrail for special trackwork, such as switches and frogs, is recommended to take advantage of findings from this study.

Xinggao Shu is a principal investigator with the Transportation Technology Center Inc. (TTCI).

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Guardrail Study: Reducing Wear, Reducing Replacements.

A detailed study of restraining rail designs and maintenance practices offers guidance for transit agencies to follow in the design, construction, wheel/rail maintenance and operation of rail systems.

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