So in order for rolling stock with different axle lengths to share tracks, they need to be dual-gauge tracks. Dual gauge track is possible with three rails only if the gauges differ by more than width of the railhead but I've heard that even this isn't possible in all locations, say on the Melbourne Suburban.

So in order for rolling stock with different axle lengths to share tracks, they need to be dual-gauge tracks. Dual gauge track is possible with three rails only if the gauges differ by more than width of the railhead but I've heard that even this isn't possible in all locations, say on the Melbourne Suburban.

With regard to Australia's 3 main gauges its possible most places except
- speed limits on BG when DG with SG on DG, not 4 rails.
- through station platforms, NG and other gauge no issue, just go gauntlet four rail track as they did in Qld, but doesn't work BG to SG and and even the NG mixed option is expensive.
- tunnels not designed for tolerances.
- any other structure in similar close distance to loading gauge not designed for.

So in order for rolling stock with different axle lengths to share tracks, they need to be dual-gauge tracks. Dual gauge track is possible with three rails only if the gauges differ by more than width of the railhead but I've heard that even this isn't possible in all locations, say on the Melbourne Suburban.

With regard to Australia's 3 main gauges its possible most places except
- speed limits on BG when DG with SG on DG, not 4 rails.
- through station platforms, NG and other gauge no issue, just go gauntlet four rail track as they did in Qld, but doesn't work BG to SG and and even the NG mixed option is expensive.
- tunnels not designed for tolerances.
- any other structure in similar close distance to loading gauge not designed for.

I'm not sure what you mean by Melbourne Suburban. Platforms 1 and 2 at Southern Cross are dual gauge.
These aren't electrified but there is no reason for them not to be.

There is a lot of dual gauge between Dynon and Sunshine which is in the Melbourne suburbs.

I understand that 3801's cylinders struck the platform in Spencer St in the 1990s but no damage was done to either the locomotive or the station. But diesel trains had used the dual gauge tracks, including sections where the third rail changed sides without problems since 1962.

I don't believe there has ever been a derailment caused by a brakeblock jamming between the two close rails although it is theoretically possible. Relatively few passenger trains use brakeblocks today (the older Comeng trains do) so if no freight trains use the line, it should be possible to remove the speed limits.

Peter

One retired boss told me he was involved with deciding speeds for dual gauge. At the time, the only dual gauge track in Victoria was the goods lines (Bunbury Street to West Footscray). The speed limit for that piece of track was 65, so that became the standard. Subsequent sections of track (North Geelong - Gheringhap) was only slow goods on broad gauge anyway, so no need or benefit to change things.

I suspect the “brake block in the gap” theory is an urban legend. Same situation would apply at any set of points or level crossing, whatever the gauge, and those trains don’t slow down.

When they re-signalled around Southern Cross a bit over ten years back, they found some ground mounted signals were being hit by sg locos; their “centre” was 3 1/4” different to BG locos. One then manager proposed reinforcing the signals to withstand the impact...I kid you not. They got around that by installing skinny signal heads.

At least on the Melbourne suburban, there are locations where dual gauge track is apparently not possible due to clearances. Consider the City Loop.

So in order for rolling stock with different axle lengths to share tracks, they need to be dual-gauge tracks. Dual gauge track is possible with three rails only if the gauges differ by more than width of the railhead but I've heard that even this isn't possible in all locations, say on the Melbourne Suburban.

With regard to Australia's 3 main gauges its possible most places except
- speed limits on BG when DG with SG on DG, not 4 rails.
- through station platforms, NG and other gauge no issue, just go gauntlet four rail track as they did in Qld, but doesn't work BG to SG and and even the NG mixed option is expensive.
- tunnels not designed for tolerances.
- any other structure in similar close distance to loading gauge not designed for.

I'm not sure what you mean by Melbourne Suburban. Platforms 1 and 2 at Southern Cross are dual gauge.
These aren't electrified but there is no reason for them not to be.

There is a lot of dual gauge between Dynon and Sunshine which is in the Melbourne suburbs.

I understand that 3801's cylinders struck the platform in Spencer St in the 1990s but no damage was done to either the locomotive or the station. But diesel trains had used the dual gauge tracks, including sections where the third rail changed sides without problems since 1962.

I don't believe there has ever been a derailment caused by a brakeblock jamming between the two close rails although it is theoretically possible. Relatively few passenger trains use brakeblocks today (the older Comeng trains do) so if no freight trains use the line, it should be possible to remove the speed limits.

Peter

Hi
Those platforms are designed for DG, others are not and some stations would be very costly to do so. Increased gap issues maybe a safety concern more so on curved platforms.

Thanks for the other info, interesting.

So I know dual gauge track is not possible on the City Loop due to clearances, but what about other locations where there also isn't room for dual-gauge track?

Presumably this is just an exercise about what is possible, but in practice, why would you want dual gauge on the Melbourne suburban network?  What SG trains would go there, and even if they could, would Metro permit them?

The new Inland Railway will have SG-NG dual gauge track, so that the old NG can benefit from the improved curves, gradients and tunnels on the new IR, This would presuamably replace the original NG line  up the range with its 1 in 50 gradients, 100m curves, and restricted tunnel (since improved) clearances of the 1860's  route.

The new Inland Railway will have SG-NG dual gauge track, so that the old NG can benefit from the improved curves, gradients and tunnels on the new IR, This would presuamably replace the original NG line  up the range with its 1 in 50 gradients, 100m curves, and restricted clearances of the 1860's  route.

This thread is about BG-SG dual gauge track. Dual gauge between standard and cape gauges may well be possible in a lot more locations, with standard rails and no special speed restriction, even for standard gauge rolling stock.
Dual gauge track between standard and Irish gauges is a different matter because of the narrow-footed rails on the dual gauge side and only being permitted where the speed limit is no more than a certain amount.
Regarding Lad's comment, any location where dual gauge track is not possible would have to be closed, probably for an extended period, if Victoria's railways were to be regauged, so knowing about those locations is an insight into why it's not going to happen.
Some other railway networks elsewhere in the world have been converted between gauges, a little at a time with dual gauge track.

Dual gauge between standard and cape gauges may well be possible in a lot more locations …

Actually not, because the difference in the track centres would be over twice as great as on broad/standard dual gauge track.

Parts of the network with just enough clearance for BG/SG mixed gauge tracks would need to have the envelope widened to clear the loading gauges for SG/NG mixed gauge track.

Some other railway networks elsewhere in the world have been converted between gauges, a little at a time with dual gauge track.

Which ones?

I'm not aware of any having been done that way since the GWR standardisations back in the mid-late 19th century.

Regarding Lad's comment, any location where dual gauge track is not possible would have to be closed, probably for an extended period, if Victoria's railways were to be regauged, so knowing about those locations is an insight into why it's not going to happen.

The policy in Victoria for gauge conversion projects has always been the opposite to your suggestion.

Rather than making dual gauge track the general policy and worrying about what to do for locations where it can't be used, the policy in Victoria is to convert a route in one go (closing it once instead of twice) and make minimal use of dual gauge track only at the specific locations where it would be beneficial.

Anyway, is it actually proven that converting from broad gauge to dual gauge would need a shorter closure than converting from broad gauge to standard gauge? I would think that the additional complexity of mixed gauge track would make it a much bigger job, and once reopened would also result in more downtime for routine maintenance.

Parts of the network with just enough clearance for BG/SG mixed gauge tracks would need to have the envelope widened to clear the loading gauges for SG/NG mixed gauge track.

Except, that narrow gauge trains in this country, and most in other countries, are narrower than our broad and standard gauge trains. Also, dual standard and narrow is allowed with higher speed limits than dual broad and standard. As noted before, but this time with more detail, three-rail dual gauge track between standard and cape gauges is possible with standard rails, but three-rail dual-gauge track between the Irish and standard gauges means narrow-footed rails on the dual gauge side.
There is a way for dual gauge track between standard and Irish gauges to be possible with four rails, that is interlaced track, and this may well need more clearance than dual gauge track between standard and cape gauges.

I'm not aware of any having been done that way since the GWR standardisations back in the mid-late 19th century.

Well, the Great Western Railway conversion was an example of the sort I mean, conversion a little at a time.

Rather than making dual gauge track the general policy and worrying about what to do for locations where it can't be used, the policy in Victoria is to convert a route in one go (closing it once instead of twice) and make minimal use of dual gauge track only at the specific locations where it would be beneficial.

That's the policy for rural railways or at least freight ones, the trains on these lines never share tracks with any suburban trains. A large, interconnected network like the Melbourne suburban or the TransAdelaide network cannot be converted in one go, it would be too disruptive, and surely neither Metro trains nor TransAdelaide has enough equipment for replacement service.
Interconnectivity within both networks also precludes line-by-line conversion. Track sharing between different routes in each City Loop tunnel is an example of interconnectivity, other examples are a depot serving more than one line.
The South Morang and Hurstbridge lines share the Clifton Hill loop and the section of double track to Clifton Hill, dual gauge track is not possible in these tunnels, so it is not possible to regauge one line while the other continues to operate.

Anyway, is it actually proven that converting from broad gauge to dual gauge would need a shorter closure than converting from broad gauge to standard gauge? I would think that the additional complexity of mixed gauge track would make it a much bigger job, and once reopened would also result in more downtime for routine maintenance.

To convert a large network a little at a time, there has to be dual gauge track during the transition. Even if done line-by-line, there may need to be dual gauge track where trains on different routes share tracks, dual gauge track is also needed during this period even just to store and maintain rolling stock and take it into and out of service.

Presumably this is just an exercise about what is possible, but in practice, why would you want dual gauge on the Melbourne suburban network?  What SG trains would go there, and even if they could, would Metro permit them?

Well, if a network is built to some uncommon gauge and dual-gauge track between it and a common gauge is possible, dual gauge track on that network could allow new rolling stock built for that network to be more standardised.

"Except, that narrow gauge trains in this country, and most in other countries, are narrower than our broad and standard gauge trains. Also, dual standard and narrow is allowed with higher speed limits than dual broad and standard. As noted before, but this time with more detail, three-rail dual gauge track between standard and cape gauges is possible with standard rails, but three-rail dual-gauge track between the Irish and standard gauges means narrow-footed rails on the dual gauge side.
There is a way for dual gauge track between standard and Irish gauges to be possible with four rails, that is interlaced track, and this may well need more clearance than dual gauge track between standard and cape gauges."

Modern narrow gauge equipment in Australia is not as narrow as you're making out. The GT42CU-AC series has a width of 2850mm and the 2800 class is 2870mm, this compares to PN's 81 class with 2968mm and the United States Domestic EMD SD70 series with a width of 3048mm. The Queensland 2800 class is 98mm narrower than the standard gauge 81 class (that's less than 5cm either side of the cab). Meanwhile the track centre of the narrow gauge line in a three rail dual gauge configuration is 184mm to the left or right of the standard gauge centre line. This means a 2800 class running on a dual gauge line will extend 138mm more to the left or right than a standard gauge 81 class running down the same line, and would actually be 94mm wider to one side than a SD70 on the same line.