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Old February 11th, 2008, 10:25 PM   #1
Electrify
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MISC | Tramways vs. Railways

Besides allowing vehicles to drive over it, is there a performance difference between girder (tram/streetcar) rail and flanged T (railway) rail? I've watched a number of different light rail videos on YouTube, and it seems almost always these trains run better on the latter than the former, regardless of right of way priorities. I know stop spacing and street regulations play a part, but is it more to it than that? Do girder rails lack traction, so it is harder for them to stop (and thus means they cannot reach higher speeds in case they need to stop quickly), or are they made to a lower standard than flanged-T?
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Old February 12th, 2008, 11:39 AM   #2
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I was going to reply in the other thread!!!

I would have thought a flanged T shape allows a greater contact area for stability and/or traction but saving on weight, or do I misunderstand what girder type rail is?
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Old February 12th, 2008, 03:36 PM   #3
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I was going to reply in the other thread!!!

I would have thought a flanged T shape allows a greater contact area for stability and/or traction but saving on weight, or do I misunderstand what girder type rail is?
Would make sense. For clairification:

Girder/tram rail:



Flanged T-rail/railway rail:

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Old February 12th, 2008, 05:40 PM   #4
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Our trams use both. I think the railway tracks are used when the tracks are not inside concrete panels.
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Old February 12th, 2008, 07:11 PM   #5
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I also bet then that the girder rail is only used in low speed areas when used on roads, and proper rail is required for faster running being mounted on sleepers.
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Old February 12th, 2008, 07:22 PM   #6
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Our trams use both. I think the railway tracks are used when the tracks are not inside concrete panels.
But do you notice a difference between velocity depending on which rail is used? Try and keep in mind stop distance as well (ie: compare speeds between two close by stops on both rails and try and compare between two distance stops on both rails).
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Old February 12th, 2008, 07:26 PM   #7
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I thought they were both the same type of track. The tram rails are just embedded on concrete, brick or whatever the current street surface is am I right?
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Old February 12th, 2008, 07:32 PM   #8
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That would make the most sense actually.
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Old February 12th, 2008, 08:35 PM   #9
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Quote:
Originally Posted by elfabyanos View Post
I also bet then that the girder rail is only used in low speed areas when used on roads, and proper rail is required for faster running being mounted on sleepers.
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That would make the most sense actually.
The tram-track has different shape. It is a "S" on its side,while the railroad-track is a "T". I think the tram-track is placed on tight curves,because it has an edge that keeps the wheels on the track(or in the trench). Railroad-tracks dont allow tight curves(trams can do 30m radius curves...have you ever seen a train doing it?).Though it can be countered with double-tracks...
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Old February 12th, 2008, 08:44 PM   #10
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Quote:
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I thought they were both the same type of track. The tram rails are just embedded on concrete, brick or whatever the current street surface is am I right?
This is tram rail sans concrete:



Flanged T-rail

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Old February 13th, 2008, 01:27 AM   #11
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Interesting. The tram rail looks like it has the benefit of it being sunk and then having the road surface poured around it, whereas the t-rail would need temporary borders put in place while the concrete sets. It looks like it's designed to transfer some of the forces into the concrete - the down-section of the the rail doesn't look as aptly designed to transfer stresses cleanly downwards to the base as does the t-rail. Saying that the stresses trams put on the tracks at 40km/h is going to be a 10th of what it puts on the track at 100km/h so it might not be an issue at tram's road speeds. I would assume that the main weight of the vehicle on the tram-rail is designed to rest on the wide flat area - I would have thought having the rim bearing pressure would wear it out and cause fatigue fractures in the trough of the tram rail. If I'm right I would say breaking performance would be little changed between the two types.
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Old February 13th, 2008, 02:52 AM   #12
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when i worked as conductor for a summer on blackpool trams (best job in the world!) the tracks chopped and changed between T shape and S shaped and it had zero effect on speed or stopping times. The S is used where pedestrians cross the tracks or when the track is on a road, if the track is running on designated lines with no public access i think they use T shaped rails as it is cheaper and more accessible for repairs.

Also an interesting problem with the S track is that if the trenched part of the track gets blocked it can easily cause derailment, this happened alot in blackpool due to sand being blown onto the tracks.
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Old February 13th, 2008, 07:51 AM   #13
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Thanks for the first hand information

I've been watching a number of light rail videos recently, as well as comparing the performance on my bus routes and metros, and am thinking the speed difference between buses and trams is not as big as it seems. I think the problem is that buses and subways sound much louder at similar speeds as trams, so it seems that trams are moving slower than they really are.
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Old February 13th, 2008, 11:35 AM   #14
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one big difference in my books

T rails --> guided turns
S rails --> unguided turns, which is why TTC streetcar don't have switches.

speed determined mostly by quality of foundation, and space in between tracks
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Old February 13th, 2008, 06:14 PM   #15
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Yeah, HK is a good example. Their double decker trams run on shoddy tracks, and run so slowly that they are being passed by buses running in heavy mixed traffic - regardless of stop spacing.
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Old February 14th, 2008, 04:04 PM   #16
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Quote:
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(trams can do 30m radius curves...have you ever seen a train doing it?).
A a matter of fact, trams can go as far as 15m radius. This is quite common with 1000mm gauge. Source: http://www.rail-info.ch/trams/VBZ/daten.en.html
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Old February 14th, 2008, 08:11 PM   #17
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I didnt know that..ours use standard gauge,and can do this(Tatra).
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Old February 15th, 2008, 12:33 PM   #18
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In Melbourne the use is varied but often normal rail is still embedded in concrete with the concrete shaped around the rail to form a groove. I think the specialized rail is used mainly where traffic is heavier. I think, but not sure, that conventional rail would be cheaper and easier to source than the special tram rails.
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Old February 15th, 2008, 01:06 PM   #19
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Quote:
Originally Posted by WotaN View Post
A a matter of fact, trams can go as far as 15m radius. This is quite common with 1000mm gauge. Source: http://www.rail-info.ch/trams/VBZ/daten.en.html
Isn't Toronto's 11m radius? It's among the tightest curves anywhere, worldwide.

As far as I can tell, while the S type has a built in curve guide (which is added as a separate piece of steel at tighter curves only for T type, see this image: http://www.tobu.co.jp/rail/torikumi/...support_04.jpg). These curve guides are actually derailment guards. You will also find them at bridges and in parts where they can fit along switches. Why bridges? (Reference image)Wind tunnels over the valleys or other passageways they cross, and this, I would be inclined to suspect, is part of the reason the tram tracks have this derailment guard built into it - every intersection is a potential wind tunnel that can slam the vehicle (yes, it would take a lot of wind to do anything, but it has happened. A Christmas Day derailment along a JR East Line express derailed due to high winds). On curves, the danger is centripedal force, the guard works by keep the inner wheel against the inner edge of the inner rail, thus it is only needed on one side, which is different from bridges where it is on both sides - however, I have seen some train lines in Japan that are 80 years old where they have this guard on the wrong side of the curve. I think in third rail systems, the derailment guard is not needed because the third rail is always on the inner side of curves (bridges on surface sections are exception). As for switches, it is in place there since there are added vibrations at switches on the inner curve side. With trams running in mixed traffic, the threat of collision with a road vehicle acts as a potential derailment threat in the event of an accident. The S rail becomes a key feature in guarding against that ever present possibility, and since it is built into the rail shape itself, this becomes an extremely efficient choice of rail shape.

On top of all that, on in-road sections, there is a constuction advantage with S type that has already been pointed out by elfabyanos. Electrify, check the Queensway section, it should be T type.

Detail showing how it guards against derailment

Presence in switches

These derailment guards are simply built into S type.
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Last edited by TRZ; February 15th, 2008 at 01:17 PM.
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Old February 15th, 2008, 01:23 PM   #20
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Quote:
Originally Posted by elfabyanos View Post
Interesting. The tram rail looks like it has the benefit of it being sunk and then having the road surface poured around it, whereas the t-rail would need temporary borders put in place while the concrete sets.
One thing that makes me wonder on this, although I beleive you are right, why would they not simply use T rail and then in the middle anchor pre-cast concrete road panels?
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