Last year KiwiRail made the decision to replace the 16 current 30-year-old EF class electric freight trains currently in use on the North Island Main Trunk with the procurement of more DL Class Diesel Trains. These EF Class trains use the 25kvAC electrification between Te Rapa and Palmerston North that was built during the Think Big years. Their decision was based on the Better Business Case NIMT Performance Improvement Report which was heavily criticised at the time especially after leaked documents possibly showed major errors with the business case, all which was covered by GA here.

This post is not going discuss the merits of the different options of the business case, but instead, address the feasibility of a highly suggested solution to this problem which is to use dual-mode locomotives. Many people including myself asked well if KiwiRail wanted to:

  • Standardise the fleet;
  • Be environmentally friendly as possible;
  • Make sure of existing infrastructure;
  • Not have the expense of closing the electrification gap;

Then why not buy dual-mode locomotives which can use both 25kvAC traction as well as have a diesel engine. It made sense, it seemed like a real win-win option so why didn’t KiwiRail consider it? Instead of endlessly speculating I did some research which led me to believe it had something to do with the current axle load limits so I just plain asked them.

This is what they had to say to my OIA on the issue:

There are very few of these full dual mode diesel-electric locomotives in service worldwide as they require a large diesel engine, and a large electric transformer, in the same locomotive body to meet the power output requirements. This is considered an impractical proposition because of limitations on the space and weight able to be used on the New Zealand network. One example of a full dual mode diesel and electric locomotive is the Bombardier ALP-45DP.

We have compared it to a DL locomotive. The DL has been used as the point of comparison because it has been designed to the maximum dimensions and weight allowable for New Zealand’s National Rail System.

  • Bombardier ALP-45DP 21.8 metres long vs. DL 18.5m
  • Bombardier ALP-45DP 2.95 metres wide vs. DL is 2.7m
  • Bombardier ALP-45DP 4.4 metres high vs. DL 3.8m
  • Bombardier ALP-45DP 130.6 tonnes weight vs. DL 108t
  • Bombardier ALP-45DP Axle load 32.65 tonnes – Bo-Bo configuration vs. DL 18t – Co‑Co configuration

Note the large difference in the axle loads with the dual mode they referenced 32.65t with the DL at 18t. This is important because the current axle load limit on the national network is 18t which means dual mode locomotives are much too heavy to be used on the network.

Of course, you may ask what if they just put a really higher spec’d locomotive as a cover. Firstly it looks like they used the locomotive pictured in this stuff opinion article on the matter which is fair enough and secondly I managed to find a dual-mode locomotive that actually runs on 1067m gauge network like ours from South Africa to compare. However, it is still slightly over our axle load limit but not much 18.7t and it is too high at 4.1m. It also has less power than the DL’s, however, they were built in 1992-1993 so maybe an unfair comparison. If someone knows a dual-mode freight locomotive that can meet NZ Rail Specs please post in comments.

South African Class 38-000

So maybe KiwiRail is correct dual-mode locomotives may not be the easy win-win solution after all.

However, I think the bigger issue here is with KiwiRail is communication. If they were a little bit more open with how they make decisions then they would face less criticism as people would understand. For example when questioned on the matter of dual-modes on RNZ’s Insight: Keeping NZ Rail on the Tracks instead of explaining the real fully understandable reason why; CEO Peter Reidy rubbished the idea by comparing it to wind powered trains. Of course, because people knew dual-modes have been around for awhile instead of addressing critics it just made it seem like KiwiRail hadn’t considered it.

But in my research on the matter, I think the really concerning thing is how poor shape our rail network is, 18t axle loads, for example, are very low compared to most countries where the standard seems to be around 25t, with many of those countries trying to increase towards 30t+. There are some lines built to 40t axle loads but are purpose built mining lines in places like Australia. Our 18t axle load limit really limits the amount of freight we can carry per wagon and thus in total. Our 1067mm gauge is not a limit either as Queensland which is also 1067mm has axle loads of 26t.

For those who may not know the axle loading of a rail network can be increased in one of a few ways

  1. Heavier/Stronger rails (Often the rails can be recycled so replacing the rails on your most important lines can be then used to improve your minor lines)
  2. More ballast which counters to extra force from the increased weight.
  3. Stronger bridges, bridges are usually the main issue when it comes to axle load limits and your weakest point as you are only as strong as your weakest bridge.

Luckily KiwiRail seems to understand the importance of this when asked in the same OIA they said:

Making provision for future increases in axle load is a balancing act, in which we weigh the incremental cost of providing for a higher axle load against the economic cost of locking the network into a lower level of future capability by not increasing the axle-load weight. KiwiRail is taking a strategic long-term view when it renews long-life assets such as rail, sleepers and bridges. As an example of this, our Structures Code requires that all new bridges be built to 25-tonne-axle load capability (based on the low incremental cost of providing for that capability). Our infrastructure route strategy sets out that limits on most major routes will be raised to a 20-tonne maximum axle load in the medium term, and then increased to 22.5 tonnes in the long term.

KiwiRail Freight Train

Any smart future strategy for rail freight should have increasing axle loading limits are one of the highest priorities. The 22.5t KiwiRail wants should be considered a minimum with aims to at least move in line with Queensland 26t or higher. This will allow KiwiRail to carry much more freight per train dramatically increasing productivity, and who knows it just may mean we might be able to run some dual-mode freight locomotives.

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  1. Would it not be possible to modify a loco? Maybe make it a little longer and add in an extra axle or two?
    Or would that still be overloading bridges etc?

    Not ideal but perhaps order them with smaller diesels installed and couple up a single diesel loco to boost the diesel operation. The electric operation should have more than enough for most of the journey and if really needed the diesel could fire up for the really hard bits? Just thinking of alternatives to having purely (that’s a bit of an oxymoron) diesel loco’s.

    1. “Would it not be possible to modify a loco? Maybe make it a little longer and add in an extra axle or two?”

      I understand that our track geometry is too tight and therefore locos and carriages can only be about 20m long. Once we get to the stage you are describing we may as well buy a diesel loco and an electric loco and run both on all trains.

      1. Your understanding is wrong, Sailor Boy. The ‘GT’ car-carrying wagon was 25.76m long and was cleared to run on all the main routes. These wagons were massive, and gave the lie to NZ’s loading gauge being particularly restrictive.

        Unfortunately they were all scrapped a few years ago, but that is a separate sad story.

        **Tried multiple times to post this comment with a link, but for some reason the message board refuses to accept it with the link, sorry**.
        Google “NZR GT wagon” and you should see it.

      2. How about a slightly different approach. Buy electric only locomotives and then purchase, or build locally, diesel generator wagons that would be coupled to the electric loco as it’s power source when not on an electrified section. The electric locos would need to be dual voltage, 1500v DC and 25v AC, so they could then operate continuously from Auckland to Wellington. This would even allow the EFs to be refurbished to extend their lives.

        1. I’m not aware of it, but with Kiwi ingenuity I’m sure we could build the necessary diesel generators and make modifications to the locos to plug the power fed to them.

          Kind of like a B unit without the traction power.

          I agree, as the network was electrified the generator wagons could be slowly retired.

  2. Vossloh AG of Germany make a dual mode locomotive called the Eurolight, and have a proposed Co-Co variant for the Asia-Pacific (called Asialight) market that has an axle load of 16 tonnes and is more powerful than the DL class locomotive. I could only find one picture of the Asialight on their general report from 2012 (and said picture is on page 35):

    1. The AsiaLight is a diesel-electric (ie no external electric supply capability), not a dual-mode electro-diesel like the ALP-45DP or the 38-000, so not relevant to this discussion.

      1. Mike: Stadler have in the ASIALight range four options.
        1. DEL/DUAL with 2800kW CAT engine/ 3000kW electric.
        2. EL 3000kW electric only.
        3. Last mile Dual with 700kW CAT engine (shunting duties on diesel),
        4. DEL with 2400kW MTU engine.
        Option 1 matches present EF in electric mode and the DL in diesel operation.
        Axle weight is 16 tonnes, so under the 18 tonne limit on the NIMT.

  3. I suspect the timeframe for increasing the axle loads might be the same as the timeframe for electrifying Auckland to Tauranga. I think dual voltage will become the bigger issue when trying to connect the gap between Waikanae and Palmerston North.

  4. Good post, explaining dual-mode limitations in NZ clearly. As you say, it’s a shame that KiwiRail hasn’t explained this very significant issue properly.

    One other limitation is power: such locos are always less powerful in diesel mode. For instance, the ALP-45DP has a max. output of 4.4MW under the wires, 2.7MW in diesel mode, the 38-000 1.5MW/0.6MW. Probably not a major issue on the NIMT (unless diesel mode is needed for the Pukerua Bay bank in the absence of 1.5kV capability), but still an operational factor.

    I think the Auckland-Tauranga NIMT/ECMT route already has a 20t axle loading, so progress is being made.

    1. Electric Freight trains climbing up to pukerua bay would suck a lot of juice from the overhead (there are already limitations on how many 8 car matangi can run in a given 24 hour period) so any dual voltage locomotives would possibly need more substations. I suspect a full load (currently 1700 tonnes for that part of the nimt) would be a big ask for the current overhead setup.

  5. The axle load is dependent on how many axles are carrying the load. In the Bombardier it is 132 tonnes divided by 4 axles (BO-BO).

    If KiwiRail specified it right using that Bombardier locomotive as an example and ran the standard CO-CO set up (6 driving axles) as per most of their locos except the DC’s (and DBR’s if there are any left) then the axle loading would be 21.5ish tonnes per axle however it may not even be that much depending on what they option above the axles.

    That is not a huge leap in weight and something that is definitely not insurmountable.

    And yes the track network needs upgrading to take it into the modern era.

  6. If the NIMT electrification is to continue operating, then the pressing imperative at the moment is to get the reliability of the current EF locomotives up to scratch. This implies the need for the “half-life overhaul”, which should have been done about 10 years ago, but the privatised railway at the time showed no interest in this. It is still not too late, but it requires a change of plan by KR management, to something that has previously been ruled out.

    If this was done, the pressure to embark on a compromise alternative strategy using new equipment of some sort would be off, and some breathing space would exist until such time as the NZ government wakes up to the need for electrification of the whole NIMT.

    As it is, Kiwirail has taken the easy-out of buying more DL’s, with a view to eventual abandonment of the electrification in the future.

    If we are to avoid this scarily backward scenario, the best and cheapest way forward is to get on and refurbish/upgrade those EF locomotives as quickly as possible.

  7. Yes, dual mode locomotives probably would not be practical for this service. Of course, the gradients Auckland – Hamilton and Palmerston North – Wellington are a lot less than for the remainder of the NIMT.
    Often in Europe, the diesel mode for dual mode locomotives is just used for the last mile, when trains do not travel at high speeds.
    In Europe dual-mode locomotives are most frequently used by private railway operators that do not have separate locomotives at the end of a long-haul run to deliver the freight waggons to their final destination. National railway operators that do have shunting locomotives stationed at many locations tend to use electric locos for electrified sections and diesel locos for non-electrified sections. For most railway companies it doesn’t seem too much of a trouble to change motive power, if they then do get the advantage of electric traction for the majority of the trip.

    On the other hand, the comparison by KiwiRail with the Bombardier ALP-45 is somewhat disingenious. Most locomotives built for European or American standard gauge railways would not fit in New Zealand. That’s why most locomotives have to be made bespoke for New Zealand.

    I totally agree with you about the communication aspect. KiwiRail has used hyperbole throughout its press releases, rather than admitting how finely balanced the decision necessarily was, even though they gave questionably greater importance to many factors that weighed in favour of diesel locos.

  8. “solution to this problem which is to use dual-mode locomotives”

    The problem is the inefficient network operation resulting from two overlapping locomotive fleets. It’s important to remember the 16 EF locomotives are to be replaced by 8 DL locomotives, which starkly highlights the greater efficiency of having a single fleet.

    That issue will be resolved when the dieselisation is complete.

    What you have raised is really a separate topic, and could be best summed up as a solution looking for a problem, as the problem already identified has already been resolved. Duel mode locomotives are not very efficient because they carry a lot of dead weight and in order to fit the two lots of equipment into a limited space (especially in the NZ context) you have to limit the capabilities (power) of the locomotive.

    Why operate a lower than necessary powered locomotive powered by a diesel engine back and forth between Tauranga and Murupara for weeks on end, carrying the additional traction equipment that won’t be utilised? Why run them between Hamilton and Palmerston North carrying a useless diesel engine with them? We would end up replacing the current inefficiency with an even bigger one.

    KiwiRail have come up with the right solution, and it should have happened years ago. The electrification was a white elephant in that the reasons for going electric at the time never eventuated. The benefits the project delivered were the track improvements and greater speeds made possible through curve easements.

    1. Geoff you are unfairly talking-down the benefits of the NIMT electrification.

      You ignore the benefits of greater acceleration of the higher-powered electrics, and the benefits of their greater reliability (until recently!) and lower overall maintenance costs.

      And then the major savings in fuel-imports (and carbon-emissions) over the whole life of the system thus far, although the cost-advantage has varied as diesel prices and electricity tariffs have gone up and down over the years.

      Of Muldoon’s “Think Big” projects, this was one of the better ones.

    2. “it’s important to remember the 16 EF locomotives are to be replaced by 8 DL locomotives”. Not True!!!!

      Read KiwiRails business case: “NIMT performance improvement”. The train plan only has 10 EF’s allocated per day out of the 16. They have already employed 12 DL’s onto the NIMT to replace EF’s. In effect making the decision before they went public. The 8 more DL’s are to finish off the remaining 10 EF’s. That way it seems like the single fleet in more efficient, but its not. The devil is in the detail.

      1. KiwiRail management decisions are unbelievably poor.
        Two examples:
        Still not prepared to accept that the railway between Wairoa and Gisborne should be re-instated. Have you seen the appalling state of SH2 between Napier and Gisborne?
        Charging $159.00 to go from Picton to Christchurch claiming it is a tourist service and ignoring locals who want to use the comfort of the train rather than the long-distance bus. ( Incidentally the cost from Picton to Blenheim, 27km, is $89.00 and takes about 30 minutes!)
        The Class 30’s should have been refurbished as dual voltage machines to run on the Wellington to Waikanae section once it too has been upgraded and electrified by whichever voltage ( cost-benefit wise) was to be used.
        There is no long-term planning at HQ, so unless we can convince whichever Government is in power to spend the money, we are going backwards instead of doing the obvious improvements.

  9. Please excuse my ignorance here. You have a standard diesel-electric locomotive where the diesel motor drives a generator which supplies current to the electric motors. Why does it need another 20t of equipment to take the current directly from the overhead supply to power the electric motors?

    1. . . . .because the overhead supply on the NIMT is 25,000 volts. The traction motors require a controllable supply of up to about 1500 volts. The 25KV therefore has to be stepped down, hence the need for a transformer.

    2. I would expect that the traction motors run at a significantly lower voltage than the transmission lines supplying them, hence the need of a transformer. The higher transmission voltage results in lower line losses, as the wires are not perfect conductors.

      Also, high voltage is not fun to work with and there’s a trade-off between how many amps you can push through the motor from a higher supply voltage vs the difficulty of insulating the windings. To add to the fun – With motors it’s all about “amps x turns”, complicated by the gotcha that more turns = more back-EMF = higher efficiency, however with higher voltage required to get the same amperage through the coils (since the windings always have resistance and (if running an AC motor) reactance).

    3. Interesting because those residential transformers you see about the place weigh about 3 tons while the larger industrial ones weigh about 4.5 tons. So it is a bit amazing that we are talking about 20 tons for something that has less to step-down and less load.

        1. Standard minipad can do 1.2MW (there are more robust ones – which makes sense when you think houses draw up to about 10kW and you could have around 100 houses running off a transformer). The industrial ones are about 2MW +/- so not that far out.

  10. The axle load issue IMO is far more important, and potentially of great benefit toward countering the massive truck weight increases that have enabled lower freight rates for trucking. 25t should be the minimum as it leaves open the possibility of stack trains in certain areas, but more realistically it enables shared use of bogies between wagon decks, which lowers running costs. More modern train braking systems would be good too.

    I would also like to see KiwiRail look at enhancing the network with some sensible line deviations. A new line from Motumaoho to Taupiri would take 20km off the journey of every Tauranga-Auckland Metroport train. That’s a staggering 40km reduction off every return trip. That will enable significant reduction in fuel use, a significant time reduction, shorter crew shifts, greater utilisation of rolling stock and lower running costs, all leading to massive savings for the cutomers on that busy route. The entire line would be straight and level, with no need for curves or grades, and I suspect the BCR of such a project would be very high. Minimum construction effort for massive gain on the busiest line in the country.

    1. That deviation has an even better reason to be created – the present line has a bottleneck in two places, at the Ngaruawahia bridge, and Hamilton city tunnel / Claudelands bridge. A derailment on the former years ago completely jammed the bridge structure, taking some time to clear, to happen inside the latter could take weeks to clear. The increase in freight traffic associated with the Ruakura inland port under construction adds even more to the payback from putting that line in.
      As an interesting thought, creating the deviation also creates the potential to use it as a wye – so trains could be routed to suit locations of major user terminals, not just at nodes.

  11. Harriet – a couple of quick comments with perhaps more later.
    If the objective is capturing traffic now going by truck, the competitive edge is extra loading gauge, not extra axle load. Axle load does allow heavier locos that can drag more, but perhaps what is needed is extra speed. Which suits electric locomotives.

    The dual mode thing is a red herring – for years, and this was quoted by former KiwiRail CEO Jim Quinn, it was considered that a change from diesel to electric at Hamilton and Palmerston North was a minimal cost, minimal hassle 10 minute job. It only became a major issue (took hours!!?) under the leadership of former KiwiRail commercial manager Iain Hill. He has since retired though is rumoured to be consulting in the rail industry…

    1. OK – the South African 38 class. The height to lowered pantograph is 4130mm, for an EF it is 3950mm – 180mm difference. Looking at the locomotive, a few easy mods to the cab would see this type easily fit NZ. 16.3m length: Tick. 2.78m width: pushing it out there a little bit probably OK. Axle load of 18.75 tonnes – marginally over but with some careful engineering, I’m sure this could be got under control.

      What I am especially interested in is the comments on that Wikipedia page that evidently proclaim the loco type as a fast runner, but also able to shunt, and with positive feedback. This indicates that this class is versatile, popular with management AND LOW COST to operate per km.

      It does not matter if the class is underpowered if: when putting 2 on the front of a train, the total still costs less than putting 1 DL on. Based on per km operating cost stats for the EF in the past, it is possible that putting 4 South African class 38s on a train would still cost less to operate per km than 1 DL.

      And that is the thing with standardisation, it only works if you are standardising on the most efficient (lowest operating cost) locomotive. Which the DL is not.

      1. Axle load versus Loading gauge priorities. If KiwiRail is mostly interested in bulk freight traffic such as coal, then increased axle load is the priority if productivity is to be improved.

        If KiwiRail is shipping export containers, it is possible that the priority is a bit of axle load increase and a bit of loading gauge increase up to a point of accommodating 3x 20ft 9ft6″ containers on a wagon which is what is hauled between Auckland and Tauranga.

        If domestic freight is the target market, then the need is for wagons of equivalent cubic capacity and shape that can compete with the large B train trucks and other combinations. It should be noted that the new weight limits for trucks has resulted in domestic intercity trucks being much longer than in the recent past; ie greater volume. In this game it is all about increasing the loading gauge for rail to compete.

        Bigger axle loads for locomotives are still very useful as they create more options for KiwiRail, but as can be seen, at a fundamental level, the path to productivity for varying freight markets, is horses for courses, not a blind obsession with standardisation at all cost.

        1. And one more – take a look at the photo of the South African class 38: panto down and diesel hitched up behind it.

          What is to stop KiwiRail from running a train from Wellington with diesel hitched in front of the Class 38 equivalent as far as Palmerston North to supply extra diesel horses, then ditch the diesel banker for a pure electric run through to Hamilton, or Auckland?

        2. The class 38 is only about 1,000hp isn’t it? Essentially a shunting loco, which highlights the point I made earlier that duel mode locos come with a trade off in power. There’s only so much equipment you can put into the avaialble space. I’m not sure having lots of lower powered locos instead of fewer higher powered locos is the way to go. At least it would certainly buck the global trend.

          One way of making the existing EF class useful without loss of overall network locomotive utilisation efficiency would be to create a situation where significantly more power is needed for the central section necessitating the need for banking. It’s a continuing pet peeve of mine that KR still operate the NIMT with 1,000 tonne trains (yes I know they get up to 1,700 tonnes, but they also get down to 300 tonnes).

          Running 3,000 tonne jobs between Auckland and Wellington with 2DL, plus EF banker for the central section, could perhaps be the goal. You would take the third loco off at Hamiton or PN even if it were diesel.

        3. Problem with running super long 3000-tonne trains (apart from the need to lengthen a whole lot of crossing loops to maybe 2Km!), is that for every little speed-restriction the whole train-length has to pass through at the restricted speed. You have to hold up all 3000 tonnes just because at any given moment a small part of the train is on a speed-restriction.

          Two separate trains of half this length-each can be brought back up to speed in half the time for a given speed restriction, meaning that where there are lots of speed-changes the overall end-end journey-time for each short consist can be significantly less than that for one long consist. This is particularly true over a route where faster sections between restrictions are fairly short and the longer consist has less opportunity to make use of the higher speed stretches.

          In situations like this, the rule is Short trains = nippy, Long trains = lumbering, even if the acceleration- and speed-capability of each is the same.

          Lumbering may be ok for time-insensitive operations, but the NIMT has quite a few time-sensitive trains, as well as exactly this geographic-profile between Palm Nth and Hamilton.

          And another thing to remember with super-long trains is that drawbar-strength limitations may require that power be distributed down the train, not all at the head end. This is no problem, but the requisite remote-control capability needs to be provided.

        4. Geoff – the class 38 is 2000hp or 1500kW electric and 800hp or 600kW diesel. Yes they were conceived as freight/heavy shunters (would perform well in the Auckland region on container trains to/from the Port of Auckland).

          However, the commentary suggests they have performed also well above expectations in general and high speed freight with their Siemens design including AC traction motors and caterpillar diesel. Tractive effort is 180kN continuous at 30kph in electric mode which is equivalent or better compared to a Dfb.

          One could scale these up to be permanently coupled twins and you’d have same output as an EF spread over 8 traction motors instead of 6, with the bonus of 1200kW of reliable twin Caterpillar diesel. Very useful system resilience and redundancy, plus ability to shunt Kariori, those inland ports, and real ports by the ocean.

          I was initially sceptical of hybrids but Harriett in her discussion has made me look again. The key is whether these South African locos can achieve ~$1/km operating cost and 70,000+ MDBF operating as pairs. If so, then these multi-purpose machines could yet be a suitable tool for standardisation.

          And by the way Geoff, I also actually do really like your suggestion to treat EFs as super bankers helping power fast 3000 tonne ECP braked curtainsider and/or container trains.

        5. “one could scale these up to be permanently coupled twins and you’d have same output as an EF ”

          But one would have nowhere near the output of a DL in diesel mode and, given Kiwirail’s plans, that is the benchmark for a hybrid..

          One of the really important aspects of problem solving is understanding the problem.

        6. ‘One of the really important aspects of problem solving is understanding the problem.’

          If one were to determine that the answer needed to be the largest and most powerful possible engine in a double cab 6 axle 108 tonne loco to our loading gauge, at the cheapest possible purchase price, and ideally hook that purchase into international dairy deals, one would end up with a…..DL

          If one was to actually take a look at the problem/task being – lowest all of life cost reliable locomotive, that contributed best toward improving KiwiRail’s competitiveness, and helped NZ achieve carbon reduction targets, then the solution might well look very different.

          The South Africa Class 38 was of interest as it is a bespoke product, which nonetheless uses proven suppliers and sub-systems to create what seems to be a pretty good piece of kit. In NZ, fully agreed that the starting point needs to be a discussion on what the problem/task is, and then a search for solutions from that point.

          The challenge is that in a highly politicised environment, consensus on what KiwiRail’s problem/task is has been problematic.

        7. Gotta agree with this dont worry to much about axle weights volume is needed.Lighter wagons will help and better lighter and larger intermodal
          containers are needed to carry what kiwirail calls domestic freight. Also refurbish the EF locomotoves as changing locomotives isnt a big deal. A lot of trains terminate at Palmerston North anyway with wagons heading east and west and ditto at Hamilton. Very soon we will have two new inland ports close to Hamilton which will require a change in running patterns.

        8. I was replying to tuk tuk came out in the wrong place but anyway geof idea to use the EF as bankers is good. They just need to be rebuilt and they could be good for another 30 years. Pslmy to hamilton is where we need the horsepower.

        9. I really think Kiwirail should electrify Frankton to Ruakura and Horotiu to get electric locos through to the new inland ports in Hamilton. If they then did something similar in Palmerston north, this would offer a really good electrified running pattern to those ports and then diesel service to PoA and PoT.

  12. The South African dual mode loco may be over height but not by much …. 300mm. Looking at it this could easily be trimmed from the cab.

    1. The new British class 88 dual mode locomotive from Stadler ( could possibly be a contender in a modified form for NZ. It weighs 86t with 4 axles (Bo Bo configuration) giving an axle load of 21.5 t. However if it had 6 axles ( either all powered – Co Co or 4 powered plu 2 unpowered -A1A A1A confiuration ) then the axle load would drop to comfortably below 18t

      1. The class 88’s diesel power is 0.7MW (on electric it’s 4MW), so the diesel is not much more than a donkey engine, not really for mainline use. Put a large enough engine in, and watch the weight increase…

        1. UK Loading gauge isn’t far off the NZ one – you can go with the smaller track gauge and the body should fit.

          The diesel engine is small – roughly equivalent to a NZ DBR class, so would be usable for light freight or passenger use. To get an idea of getting a larger capacity diesel engine into the same body shell, look at the Class 68 with just over 3,000 more HP than the 88 and no overhead equipment. (

          Axle loads (and curve radius) were a reason why the EFs came as BO-BO-BO rather than a CO-CO

  13. Just thinking about the issue another way – are there any viable battery options that would allow dual voltage electrics to cross the gap in the NIMT now covered by the diesels?

    I am guessing the power/weight requirements are not quite there yet, but it would be neat if a big battery could be taken on and off the train as another carriage. A battery/recharge tender?

  14. Informative article.

    Agree with Dave B. 100%. It would be foolish to go backwards in our transport infrastructure and abandon the electrified main trunk, just when cost of diesel is high, and we have abundant clean energy from hydro and new wind projects. We as a country must look to the future. Maintain our existing EF class locos while completing main trunk electrification. In the end it will cost less while also being more environmentally friendly.

    Using a dual-mode electric/diesel loco for long-distance haulage is a bit of a red herring as to my understanding, dual mode locos are used mainly in electric traction mode and the diesel is there to move the train at low speed in the yard or on local lines etc.

    Also, our axle loading and loading gauge limits are a joke. As is the state of maintenance of our main rail lines. Compare with narrow gauge in Australia and you’ll see the difference immediately.

    The bigger picture being missed by Kiwirail and even in this article, is that if our rail infrastructure (track and rolling stock) had been suitably maintained and extended over the last decades, we would not have this conundrum now. Rather than letting it get worse, let’s bite the bullet and put it right. This may involve greater investment now than some other options, but long term is the only sensible option. How many developed countries are throwing away their 25 kV infrastructure and moving to diesel? I bet none.

    1. I think Kiwirail are caught in between a rock and hard place. Uncertainty of funding & years of under funding until perhaps more recently. Rising maintenance costs of the EFs. Even if we were to electrify the rest of the line, would take a number of years…years to even decide exactly who/how when even. Seems from my limited understanding duel ones are just too gutless in diesel mode for what NZ needs in this scenario.

        1. Duel cabs no longer turn me on. It could be we have reverse polarity within KiwiRail. Nothing that a down-to-earth bright spark couldn’t solve…

      1. Would someone in the know like to explain just what is causing rising maintenance cost for EFs. They are getting on in years, but surely standards ongoing maintenance should keep them in shape. What are the wear parts that now require major overhaul?

        1. The EF brain needs an upgrade – the traction control system. The DX and DF series have had multiple traction control system upgrades over many years. The EFs have not had any of that. The EFs that were repainted into KiwiRail colours received a “Dulux” overhaul. Refer to this link for a useful introduction to the Advisian report in one of the RMTU newsletters – (page 13)

          Depending on whose numbers you believe, even now the EFs are still cheaper to run per km than a DL, however just a couple of years ago they cost one third as much per km.

        2. Thanks for the info. So I understand the EF is harder to control than the newer systems, and therefore probably not up to standard in relation to safety. I wonder what the cost is to retrofit up-to-date control systems.

          Didn’t the DL class also needs such upgrades over its life–why is fitting this to the EF so problematic? Or perhaps it isn’t, as we have not seen any numbers. (May be buried in the reports you mentioned so I’ll take a look later.

          Interesting times. Just wish central and local gov’t would get on board with this and fast-track it to get underway immediately and running 5 years from now, rather than probably a couple of decades… after spending billions on Waterview connection with questionable business case, gov’t balks at much cheaper projects with major tangible benefits for key regions of upper North Island. (One hopes with that successful, further connections to Palmerston North, Napier and Wellington might be added in the future.

          I wish rail would be brought to North Shore, and the analysis says train much cheaper than proposed 2nd road harbour crossing concepts. But that won’t be or a while,a nd as others have pointed out, getting to Wellsford then Whanarei is expensive and challenging geographically. However, with the unexpectedly rapid expansion of Albany and surrounds it would make a lot of sense to get on top of this problem early.

  15. Dual mode locomotives from Stadler. See

    It dismays me that at a time the world is moving away from diesel due to its impact on the environment, and the health of humans as well as animals, KiwiRail come up with the excuse that what they will add in the way of pollutants isn’t very much in the scheme of things on a worldwide basis. KiwiRail as a taxpayer owned operation ought to be taking the lead in reducing reliance on fossil fuels as per our commitment to the Paris Climate Accord, and making full use of the existing electrical infrastructure on the NIMT. It should also be urging Government to extend electrification. The obvious next phase is the completion of electrification between south Auckland and Te Rapa, which should be set as a priority. In the interim the EF locomotives on the NIMT can be re-fitted with modern controls at a fraction of the cost of replacing them, and thus extend their operational life by 20 – 30 years.

    We have the Northern Explorer running through pristine countryside spewing out cancer causing pollutants that can end up in the food chain. I did that trip recently and was confronted additionally by two DLs at National Park, puffing out fumes, whereas I had hoped to see two EFs hauling the same freight load.

  16. The actual Axle load capacity of the current 50Kg/m rail that has been in use for about 25 years in New Zealand is 28 tons.
    Most rebuild work on the ” Golden Triangle” like bridges etc has been done to a 23 or 25 ton axle load.So heavier locomotives and wagons could be used on this line. The limiting factor, is the Kaimai tunnel, as the fumes take a ;ong time to clear.

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