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When riding the CTA Blue Line, I have noticed that there are often 1 or 2 extra rails between the main running rails.  Someone once said these were safety guard rails in case a derailment occurred.  I always thought guard rails needed to be quite close to the main rail, approximately a flange width away or so.  The seem to be at least 6 inches away if not more.  The rails are noted by the red arrows in the attached picture.  They are not as hefty as the mail rails, but they do have some size to them.  The look similar to the electrificed 3rd rail in many ways.  Coluld they be a grround or electrical return?





Please help me understand the purpose of these rails.



Images (1)
  • SnipImage
Last edited by Gpritch
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Hello Gpritch---


Those generally are "guard rails" rather than what are usually called "FLANGE-RAILS OR FLANGE-CHECK-RAILS".  Flange check rails are spaced very close to the inside face of the running rail to actually slightly engage the back side of the flanges on wheelsets riding the inside rail of the curved track. 


They form a "slot" effect so as to guide the subway car trucks' inner wheelsets and their flanges around the inside rail of any moderate to sharp curves.  They also prevent the wheelsets and their flanges on the opposite side of the axel, operating on the (usually higher, super-elevated) outside rail of the curve, from riding up and over that rail.


The "guard rails" shown in your Chicago CTA trackage photo are unusually close to the center-line of the track than would normally be.  Likely because its a surface running track. 


Check the photos attached here from my 2-rail track O-Scale N.Y. City Model Transit System EL  layout trackwork.


This is typical of New York (and other applications) style track for many past decades to present.  On older systems, the straight express track usually did NOT have any inside guard rails.  ONLY both local tracks did because of their close proximninity to the edge of the El structure.


On modern day trackage, some express tracks do have inside guard rails, others do not.


On my CURVED tracks, see the GUARD rail moving inward away from the running rail as the FLANGE CHECK RAIL begins and is close to the running rail.  This is prototypical and standard on all EL's


Outisde of each track are wooden GUARD TIMBERS whcih serve to keep the ties in alignment with each other (from shifting) and also serve at outer auxiliary guard rails.


Regards - Joe F






Images (4)
  • 017_17: Running rails, guard rails and 3rd rails
  • 021_21: Running rails, guard rails and 3rd rails
  • IMG_3300: Curved track Guard Rails and Flange check rails
  • IMG_3306: Curved track Guard Rails and Flange check rails
Last edited by Joseph Frank

CTA says this:



Q: I wanted to know about the smaller gauge tracks that are inside the regular tracks on some portions of the "L" . Were they old wide gauge tracks, then at some point the trains changed to standard gauge, but the old ones never removed? Or were they both used at the same time?

A: There are two types of those old rusty tracks you see inside and along "L" tracks.

The first type, which are seen on the North Side and Evanston Divisions, were separate tracks for freight operations. They are the same gauge as the "L" tracks, but are a second set of tracks offset from the "L" tracks by several inches. One track is between the "L" tracks and the other is outside the "L" tracks. They allow wider freight trains to clear the "L" platforms by creating a second set of tracks within what is essentially a single-track right-of-way. This is called a "gauntlet". These are no longer in use.

The second type has both rusty tracks between the "L" tracks. These rusty, usually grime covered rails are called "Guard Rails." They are to prevent a disaster in the event a train derails.

On a straight-away, whether a derailed truck goes off the running rails to the left or right, it can only move six to eight inches before the inner side of the wheel flanges contact the guard rails. So even though the wheels are bouncing on the ties, the derailed truck would not be able to swing left or right, far enough, to allow the train to go over the edge into the street, or cross over into an oncoming train. (And, just as important, the derailed truck would not be able to swing to the 70-90 degree point where it would break off under the car forcing equipment, mounted under the car, up through the car floor. Ghastly thought, no?)

On sharp curves, crossovers (switches), crossings, and interlockings, other types of guard rail technologies are used.

For example, on crossings and switch frogs the guard rail is typically a fabricated component of the running rail. The wheels ride on the outer rails, and there is a gap of several inches for the wheel flanges, then the inner rail. This virtually eliminates the chance of a derailment, while the truck is passing over the assembly. The straight-away type of guard rail is often used as an entry device, just before the switch or crossing, to guide a derailed truck to a more stabile position before it hits the points, frogs or crossing-track.

On very sharp curves, as in a CTA yard or in the Loop, yet another technique is used. On these tight curves the leading wheel of each truck will try to climb over the outside rail, no matter what speed the train is moving. This effect is especially pronounced if both the wheel flange and the rail are dry. Part of the solution is a contraption which may be called a "flange greaser." Just before the train enters one of these areas the wheels contact a pedestal along side the running rail. The pedestal operates a pump connected to a grease reservoir and as each wheel goes over the pedestal, a very small amount of grease is pumped out where the wheel flanges can pick up a little. So, over time, the grease migrates throughout the curve or interlocking track. This reduces the rail-climbing tendency, and has the secondary effect of reducing the volume of that earsplitting squeal as the train rounds the corners in the loop. This accounts for the amount of heavy black grease on the ties and guard rails one usually sees when you pass an interlocking plant.

(Thanks to retired-CTA worker Peter A. Christy [Badge #23234] for providing the answer to the second part of this question!)


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