Train / Tram Level Crossings

[Gwiwer]

The subject of train / tram level crossings has cropped up today in Early Risers and included a link which directed me to clips I was not previously aware of showing these uncommon locations in operation.

 

Aside from operational curiosity such things would make a fascinating model.

 

Railway / tram level crossings used to exist in some cities in rather larger numbers than they now do.  Melbourne, home to the World's largest tramway network, retains four though by the end of 2015 that figure will reduce by 25% to three as one is about to become grade-separated.  There were once more than a dozen such around the city.

 

Those which survive are at Kooyong, Gardiner, Riversdale and Glenhuntly.

 

The first link shows that at Riversdale where tram route 70 crosses the sleepy Alamein suburban branch line.  Amid the detail shown check the gradient the tram has to cope with at 2m 10s and the well-worn condition of all the infrastructure.  With trains and trams crossing every few minutes all day every day it takes a fair hammering.  Riversdale was rebuilt very recently; this clip is pre-rebuild 

 

 

Then we see the unique Glenhuntly crossing.  Unique because while the three others have two tram and two train tracks Glenhuntly has three train tracks and alone among such locations also sees freight trains crossing the tram lines.  Tram route 67 crosses the very busy Frankston passenger line which also sees double-headed freights to around 3000 tonnes to and from the Long Island steel works.  At this location the two outer rail tracks are the conventional up and down roads and there is a middle reversible road.  This is used in the morning peak by up expresses as an overtaking lane while down trains use the down track; at all other times it is used as the down track with evening peak stoppers using it while expresses use the down road to run through.  The clip has been shot during the morning peak as it shows a down stopper on the down road and an up express on the reversible.

 

 

Gardiner and Kooyong closely resemble the Riversdale crossing.  Both are on the suburban Glen Waverley line which is therefore unique in having two tram crossings with tram 72 crossing at Gardiner and 16 at Kooyong.  Gardiner is about to be grade-separated as the road is particularly busy here being adjacent to the major Monash Freeway interchange.

 

Operation is not straightforward.  Trams operate on 600V and trains on 1500V.  Trams run on standard gauge track and trains on the "Irish" broad gauge of 5' 3".  At each crossing, referred to as a "square" locally, there is control cabin.  Default voltage is the railway 1500V current; if that were fed to a tram it would fry the electrics and potentially cause a fire.  When trains are offered the booms close to road traffic automatically based upon electronic approach control.  Approaching trams which for the most part are driven on line of sight are obliged to obey a red / green signal on the approach to each square; this remains red by default.  The tram tracks have facing "derails" which are by default open and will divert a tram to derail towards the footpath.

 

When the booms are raised and a tram requires to cross it must first stop at the signal and sound its warning gong.  The controller will confirm there is time to allow it across and will then isolate the railway traction current over the square, switch in the lower tramway voltage, close the derail by electro-mechanical control and switch the signal to green.  The tram proceeds and unless another has already been admitted (either in the opposite direction or closely following) the controller then restores the signal to red, opens the derail and switches the overhead back to railway voltage.

 

Trains are restricted to 20kph when crossing (15kph at Kooyong and Gardiner owing to poor condition of the squares there) and trams must cross at "walking pace" though the precise definition of that seems to be stretched in both clips.

 

 

 

[Edwin_m]

A fascinating bit of engineering, but no doubt a nightmare for those who have to operate and maintain it.  If both systems use pantographs I would have thought there is a risk of one "hooking" the other wire - or are these parts of the tram network restricted to trolley poles? 

[SRman]

There are no trolley pole trams left in operation in Melbourne, now. All operational trams that used to have them have been fitted with pantographs.

 

There is some good footage in those two clips, Rick.

 

I work at a school just near the Riversdale Road crossing, literally within earshot of it! My office window overlooks Riversdale station itself, and the Prospect Hill Road level crossing, which does not have trams but does have equally awkward gradients on its approaches. The railway line itself has a quite fearsome downhill gradient coming off the flyover over the Lilydale/Belgrave line tracks coming out of Camberwell.

 

Train frequencies off-peak are every 15 minutes in each direction, while the trams are slightly more frequent at every 12 minutes. Peak hour frequencies are higher, and additionally trains are six cars long and run through to the city, where off peak they shuttle between Camberwell and Alamein. A class trams are the norm on route 70 along Riversdale Road, but the articulated B class do some peak hour or school time runs. One of the B class features in the clip shown.

[Edwin_m]

A post on a tram overrun at one of these crossings, plus some other technical stuff, has appeared on The Signal Box:

 

http://forum.signalbox.org/viewtopic.php?f=10&t=7038

[Gwiwer]

I know of no instance of pantograph entanglement.

 

All pans are gently curved and present the concave face to the contact wires.  More so in the second clip it is easy to see that the outer edges of both train and tram pans curve down away from the points of contact so there is no real risk of snagging the cross wire.

 

What can be seen on the second clip is that there is either some wear to the crossing pans (the large metal "frogs" in the overhead where contact wires meet at right-angles) or a very slight misalignment of some overhead which may be caused by wear and tear.  The second train shows it best once the first one clears - watch the pantograph heads closely at around 1m 50s and you can see that they rock as they negotiate the crossing pan.  That's not a problem so long as speed is maintained at the permitted limit.  Very occasionally a crossing pan will drop from one of the four points of attachment through metal fatigue or failure.  This is called a "tilted pan" and requires services to stop until it is repaired or replaced.  If struck by a passing rail or tramway vehicle that can cause terminal damage to the pantograph.  A tilted pan can be replaced by the overhead line crew in around 30 minutes; a lot less if it only requires reattaching at one point.

 

As Melbourne's tramways undergo progressive replacement of outworn infrastructure older style overhead components such as heavyweight cast metal crossing pans and frogs are being replaced on street-corner intersections.  They were needed for trolley-wheel pole-fitted tams but pantograph trams can traverse from wire to wire without them.  In theory they can also be replaced at the rail squares but have not been; that would not eliminate the need to switch voltages and manually signal trams across so the existing system is retained.   

[phil-b259]

 

Operation is not straightforward.  Trams operate on 600V and trains on 1500V.  Trams run on standard gauge track and trains on the "Irish" broad gauge of 5' 3".  At each crossing, referred to as a "square" locally, there is control cabin.  Default voltage is the railway 1500V current; if that were fed to a tram it would fry the electrics and potentially cause a fire.  

 

I assume both voltages are DC?

 

If they are then one obvious thing to do is borrow what happens at the French / Itallian border. The French network in this aerea is electrified at 1500V DC and the Italians normally use 3000V DC and it doesn't take a genius to realise that this means that so Italian locos can quite easily be used on the 'French' system - they are just a tad under powered.

 

Thus surely it would have been possible in the Australian case for the entire OHLE at the crossing to be energised at 600V - thus removing the need for complicated switch arangements.

 

[Gwiwer]

Both systems are DC.  There is a strong case to argue that the tramways should be upgraded to 750V in order to better cope with modern traction packages and the added demands of air conditioning.  All renewals are now done to accommodate a future upgrade but the power centre cannot be upgraded and an all-new one will be required at considerable expense.  This is only in the very longest term of future planning.

 

The railways could arguably be better managed if 25kVac were available but it isn't and is not likely to be.  There is no ac railway electrification anywhere in the State of Victoria.  1500Vdc is an old system and again new trains don't run as well as they might on that current.  However with a significant suburban network of 15 lines and a large fleet of rolling stock any major changes will cause enormous disruption.

 

It is electrically possible to have the voltage across the tram squares permanently at 600V without switching but this would probably bring the trains to a stand.  They require more potential than that to move.  Even at 20kph they may well stall and possibly be unable to re-start if only 600V were available.  

 

I am also not too sure of the electrical implications when one runs through a significant voltage change as opposed to stopping and flicking a switch in the cab (at the minimum) to change systems.  Would the surge create an unacceptable jerk in the motion or to much stress on the couplers?  Would it knock out the circuit breakers?

 

I'm no electrician but I am reasonably sure that after almost 100 years if there were abetter way of doing things it would by now have been done.

[phil-b259]

Both systems are DC.  There is a strong case to argue that the tramways should be upgraded to 750V in order to better cope with modern traction packages and the added demands of air conditioning.  All renewals are now done to accommodate a future upgrade but the power centre cannot be upgraded and an all-new one will be required at considerable expense.  This is only in the very longest term of future planning.

 

The railways could arguably be better managed if 25kVac were available but it isn't and is not likely to be.  There is no ac railway electrification anywhere in the State of Victoria.  1500Vdc is an old system and again new trains don't run as well as they might on that current.  However with a significant suburban network of 15 lines and a large fleet of rolling stock any major changes will cause enormous disruption.

 

It is electrically possible to have the voltage across the tram squares permanently at 600V without switching but this would probably bring the trains to a stand.  They require more potential than that to move.  Even at 20kph they may well stall and possibly be unable to re-start if only 600V were available.  

 

I am also not too sure of the electrical implications when one runs through a significant voltage change as opposed to stopping and flicking a switch in the cab (at the minimum) to change systems.  Would the surge create an unacceptable jerk in the motion or to much stress on the couplers?  Would it knock out the circuit breakers?

 

I'm no electrician but I am reasonably sure that after almost 100 years if there were abetter way of doing things it would by now have been done.

 

Could the trains not simply 'coast' through the section (much as they do with isolating sections on ordinary track)?

 

My thinking is that while they may not be enough power for a 1500V train to acelerate etc at 600V, generally speaking feeding electric components rated at 1500V with 600V is unlikely to do permenant harm. Doing it the other way round on the other hand - would, as you say, deffinately result in some severly flambéd kit.

 

Of course it may be that at the time the origional installation was constructed electrics / electronics were not advancded enough to cope with the situation and it simply hasn't been cost effective to change what is already installed.

[Gwiwer]

I suspect your final sentence is closest to the truth.

 

Trains can coast but over the distance required - and given that many have barely moved away fro a station stop and are drawing high current to get moving at all - it's not ideal.

[Gwiwer]

Here are Kooyong (first up) and Gardiner to complete the set

 

At 0m 35s you can clearly see on the road surface what happens when a tram derails and five seconds later you see a typical example of Melbourne driving - notice the tram is the one facing a green traffic light.

 

At these older style squares the train wheels actually ride up as the bogies traverse the crossing meaning that for a short distance the train is travelling on the wheel rims only.  As this reduces friction it increases the chance of sudden wheel spin and is one reason the speed must be kept so low.  To spin just a few wheels while under power could be catastrophic.  This was necessary due to the design of the crossing rails since railway wheels are larger than tram wheels and have deeper rims.  Recently rebuilt crossings at Riversdale and Glenhuntly have a new design which permits the flanges to remain in contact with the rail head at all times.  Playing the Glenhuntly clip and then any of the others (the Riversdale clip is pre-rebuild) the difference in sound can be detected as trains cross.

 

Other things to spot here are at 3m 15s (Kooyong) where the train bogies can clearly be seen riding up as the train crosses the square, at 4m 20s the miniature boom gate for trams required by the road layout at Gardiner, and at 6m 58s (Gardiner) when a person has walked onto the railway right next to the departing train - something else which occurs many times daily and is too easy thanks to the absence of any physical protection remembering this is the "departure" side for road traffic.

 

[kevinlms]

Here are Kooyong (first up) and Gardiner to complete the set

 

At 0m 35s you can clearly see on the road surface what happens when a tram derails and five seconds later you see a typical example of Melbourne driving - notice the tram is the one facing a green traffic light.

 

At these older style squares the train wheels actually ride up as the bogies traverse the crossing meaning that for a short distance the train is travelling on the wheel rims only.  As this reduces friction it increases the chance of sudden wheel spin and is one reason the speed must be kept so low.  To spin just a few wheels while under power could be catastrophic.  This was necessary due to the design of the crossing rails since railway wheels are larger than tram wheels and have deeper rims.  Recently rebuilt crossings at Riversdale and Glenhuntly have a new design which permits the flanges to remain in contact with the rail head at all times.  Playing the Glenhuntly clip and then any of the others (the Riversdale clip is pre-rebuild) the difference in sound can be detected as trains cross.

 

Other things to spot here are at 3m 15s (Kooyong) where the train bogies can clearly be seen riding up as the train crosses the square, at 4m 20s the miniature boom gate for trams required by the road layout at Gardiner, and at 6m 58s (Gardiner) when a person has walked onto the railway right next to the departing train - something else which occurs many times daily and is too easy thanks to the absence of any physical protection remembering this is the "departure" side for road traffic.

 

Great videos Gwiwer.

 

A couple of other comments.

 

1/ Notice the gouge in the roadway, where a tram has derailed at the catchpoints just before the crossing.

2/ Is not clear in these shots, but some of these crossing have (or perhaps did until recently) rotating disc signals (standard McKenzie & Holland items) for the trams.

http://www.signalbox.org/overseas/australia/kooyong.htm

Just as well only applicable for trams, as the average driver, wouldn't have a clue, regarding a disc signal!

 

3/ Although an interesting piece of history, where else but Melbourne would you have such a piece of infrastructure so close to an important freeway exit?

https://www.vicroads.vic.gov.au/planning-and-projects/melbourne-road-projects/burke-road-glen-iris-level-crossing-removal

[Gwiwer]

 

 

Great videos Gwiwer.

 

They illustrate the operation very well though they are not my work.  

 

The rotating disc signals have gone from the tram squares.  A very few still exist on the suburban railways controlling entry / exit at yards and sidings.  Frankston is one such location where one post has two and another has no less than four on a post.

[Grovenor]

Perhaps just to clarifyb for those of us used to English Railway terminology.

At these older style squares the train wheels actually ride up as the bogies traverse the crossing meaning that for a short distance the train is travelling on the wheel rims flanges only.  As this reduces friction it increases the chance of sudden wheel spin and is one reason the speed must be kept so low.  To spin just a few wheels while under power could be catastrophic.  This was necessary due to the design of the crossing rails since railway wheels are larger than tram wheels and have deeper rims flanges.  Recently rebuilt crossings at Riversdale and Glenhuntly have a new design which permits the flanges  treads to remain in contact with the rail head at all times.  Playing the Glenhuntly clip and then any of the others (the Riversdale clip is pre-rebuild) the difference in sound can be detected as trains cross.

Usually described as 'flange running' and common on tramway track design to keep noise down.

Regards

Keith

[Edwin_m]

Why does flange running reduce friction?  Friction doesn't depend on the area of contact - is it something to do with the flanges being less clean than the treads? 

[phil-b259]

Why does flange running reduce friction?  Friction doesn't depend on the area of contact - is it something to do with the flanges being less clean than the treads?

 

What is key here is to understand the behaviour of the rail and wheel interface. When examined under the microscope the wheel actually depresses the railhead ever so slightly and sort of stick together briefly thus providing good traction. When wheelslip occurs this relationship has broken down due to contamination altering the friction coefficents. In general train wheel flanges (as opposed to tram profile wheels) have thin flanges so while the applied force is grater, because of the reduced surface area the weight is applied over the tendency to slip will be grater.

 

Incidentally one of the big problems with the tram-train project in the UK is trying to design a suitable wheel profile that can be used on NR and tramway track given the big differences in tolerances and the ideal wheel profiles required for each.

[Edwin_m]

Not sure I agree with that Phil.  Railway flanges are indeed thinner at the base (but thicker higher up) but a train doesn't ever run on its flanges.  Flange-running trams have a flange which is thinner but less deep with a flat area underneath, as with a sharp point the forces would probably be enough to cause plastic (permanent) deformation in the flange or the rail. I still can't see how this affects the coefficient of friction. 

 

I agree the wheel profile is a challenge for tram-trains because a flange thick enough not to derail on railway pointwork is too big to fit in the groove on street track (a bit like trying to run a finescale model on coarse scale track).  The normal solution, as applied to Manchester Metrolink, is to make the wheel thicker above rail level and to fit a raised checkrail on the railway S&C used by the tram-trains, which engages with the thicker part of the wheel. 

[Gwiwer]

Railway wheels are of different profile to tram wheels.  On the old style crossings in Melbourne they also ride up and clear of the tram rails by running briefly on the rims (or flanges if you prefer) hence as each wheel passes across the tram track contact is briefly lost with its own running rail altogether.  That has been addressed in the recent rebuilds of Glenhuntly and Riversdale to allow a deeper groove for the railway wheels to travel through meaning they remain in contact with the rail but exert less downward force than is normally the case.  I believe these rebuilds also included rubber footings to accommodate some of the hammer blow.  Despite that the Glenhuntly crossing is already showing significant signs of wear.

[Grovenor]

 

On the old style crossings in Melbourne they also ride up and clear of the tram rails by running briefly on the rims hence as each wheel passes across the tram track contact is briefly lost with its own running rail altogether.

Do you really call flanges 'rims' in Victoria? Wasn't the case in SA or NSW when I worked on the railways there, granted that was 25 years ago.

Keith

[Gwiwer]

I guess it depends if you learned your jargon on the tramways or the railways.  On a similar theme the crossings are "tram squares" to railway staff but "rail squares" to tramway staff.

[phil-b259]

Not sure I agree with that Phil. Railway flanges are indeed thinner at the base (but thicker higher up) but a train doesn't ever run on its flanges.

If you carefully read what Gwiwer has written it would appear that while transiting the crossing shown trains do run on their flanges for a short distance. He also comments that carefull handeling is required to prevent wheelslip as a result.

 

I fully accept that the situation doesn't arise in the UK though.

[Edwin_m]

@Dutch_Master

 

I've spent some years on and off doing feasibility studies for tram-train for the UK.  One of the issues is that check rails on the Continent are normally raised, but those on Network Rail are mostly level with the top of the running rail so would need modification to work with tram-trains. 

 

@phil_b259

 

Yes Gwiwer does say this, but I would be grateful if someone could explain how flange running leads to poorer adhesion, since it seems to me to contradict the rules of physics. 

[PhilJ W]

The Glasgow trams used a gauge almost an inch less than standard to allow railway goods wagons to be moved over their tracks between the various industry's on Clydeside, the wagons ran on their flanges in the tramway groove. When loaded there could be two tons or more on each flange.

EDIT. I have just read Edwin_m's post above, it would be interesting to know if the locomotives used in Glasgow were 'tramway' gauge or standard gauge. Some of the locomotives were electric running off of the tram overhead but some were steam and could venture onto normal track.

[EddieB]

Standard references (e.g. "History of the Steam Tram", Whitcombe) quote a track gauge of four feet seven and three-quarter inches.  Unfortunately the locomotive listers may have adapted their compilations to reflect this unusual gauge and it isn't clear how the locomotives were specified in the builders' records.  For example, I have seen both 4'7 3/4" and "standard" given for the Hughes tram locomotives and 4'7 3/4" and 4'7 5/8" for those built by Kitson.

[dullsteamer]

I guess it depends if you learned your jargon on the tramways or the railways.

I dunno, the blokes I talked to Preston who operate the wheel lathe certainly call them flanges...

 

Cheers,

 

Mark.

[dullsteamer]

Of course it may be that at the time the origional installation was constructed electrics / electronics were not advancded enough to cope with the situation and it simply hasn't been cost effective to change what is already installed.

That was probably a factor, but I also wonder how much co-operation there was in those days between VR, who ran the railway, and the M&MTB who ran the trams?

 

Cheers,

 

Mark.