Modernising the infrastructure to make the trolley buses pay

by Kerry Wood
The Wellington Regional Council has seen trolley buses as costly and outdated, and has even asked on the consultation form … how do you think the additional costs should be paid for? This question must be seen in the light of a series of errors and missed opportunities:

• Modernising the trolley infrastructure is about a third cheaper than upgrading, because the system can be optimised: around $34 million instead of $52 million.

• Closing the trolleys will cost nearly $20 million. A fair comparison would add this to the cost of replacement diesels, a total of $42 million: modernised trolleys would be about 20% cheaper.

• Trolley systems are seeing a renaissance as diesel costs rise, climate change kicks in and the health risks from diesel emissions are better understood.

• Battery buses are already an excellent complement to trolleys and may displace trolleys in time. But at present, trolleys have option value.

• Some problems are self-inflicted. Rundown equipment needs emergency maintenance. The trolleys are helpless off the wires, despite battery back-up. They are ‘too slow’ but experienced drivers disagree. So do the Swiss, who run trolleys at ordinary bus speeds beneath complex ‘overhead’ wires. See

• A mistake in the Pricewaterhouse Cooper study has spawned a series of obviously nonsensical statements about emissions. Trolleys already have much greater benefits then hybrids—let alone diesels—and will be better still with an upgrade.

Modern trolleys

Like trams, trolley buses have gone from obsolete to modern as their advantages are realised and their defects overcome. There is world-wide interest in trolley systems, and especially trolleys with modern batteries, running beyond the end of the wires. Over 700 new trolley buses will be delivered this year.

In 2012 an all-new trolley system opened in Saudi Arabia, and now Montreal and Leeds are planning all-new systems. Leeds will have electric BRT from 2018. Many existing systems are expanding. Shanghai has abandoned battery bus trials and is planning a comprehensive modernization of its still-extensive trolleybus system.

With today’s technology a Wellington trolley bus can have a range of about 30 kilometres off-wire, and battery buses with larger (heavier, pricier) batteries can already manage 150 kilometres.

Today’s battery buses need either an easy schedule or top-up charging during the day. The best solution will be the cheapest compromise between how often they are charged, how much the charging-points cost and how much charging delays the bus. That is not settled, and widespread use of battery buses would be premature.

Frequent charging is good for the battery but needs more charging points, each with a heavy-current power supply. This is where trolley overhead comes in. A battery/trolley bus can take its charging ‘pause’ not at a charging point but under the overhead, whether bowling through Island Bay or boarding passengers at the Railway Station.

Modernising the Wellington system

Wellington is in a very unusual position: modernising the trolleys is cheaper than either repairs or replacement because the timing is right.

• Modernising a substation costs the same as simple replacement.

• A modern voltage needs fewer substations: half of them can be scrapped.

• The buses need modernising too, but this costs less than the saving on substations, as well as making the trolleys much more efficient.

Wellington’s trolleys run at the old tram voltage: the early overhead was just a second wire on the tram overhead. Modern 550 volt equipment is almost unobtainable.

The trolleys have already been rebuilt and modernising needs little more than new motors, control systems and batteries, around $100,000 for each bus, $6 million for 60 buses.

A higher voltage can supply the same power from fewer substations: seven is a conservative replacement for the present fifteen. Two substations have been done so only about another five need replacement.

Five new substations designed for 750 volts will average just under $1.0 million each (some equipment has already been replaced), and another $2 million each for replacing feeder cables, a total of $14 million. Add another $6 million for upgrading the buses and a conservative $10 million for contingency and project management, and you have a total of about $30 million. Add another $4 million for possible other changes (the secondary spine might need wiring, or an additional substation) and the total cost is around $34 million, down from $52 million for a 550 volt upgrade.

Quality diesel buses cost around $370,000, $22 million for 60 buses, plus $20 million for closing down the trolleybus overhead, total $42 million.

Wellington’s trolley buses were built in 2007–09 and can be expected to last about twice as long as equivalent diesels. They could easily be running in 2030.


The main nasties in vehicle emissions are carbon dioxide (the most important greenhouse gas), nitrous oxides (respiration problems) and ‘particulates’. The tiny particulates are the most dangerous, less than a ten-thousandth of a millimetre. They can find their way into lungs or even the brain, and are Class 1 carcinogens.

‘Clean’ diesel engines remove larger particulates and nitrous oxides but are little better than ‘dirty’ engines for fine particulates. On greenhouse gas emissions they are worse than older engines because the clean-exhaust systems make them less efficient.

Modernising the trolleys will lift their energy efficiency from 70–75% to 90–95%. They will then run nearly three times as far as a diesel bus for the same release of greenhouse gas emissions, with very low particulates and zero local emissions (the emissions are at the power station).

The best approach will be a series of small steps, with research and trials to confirm costs and decisions. The optimum start date is about 2014: there is research to be done.

Kerry Wood is a retired Wellington engineer with a long-standing interest in transport matters. This article is based on his submission to the regional council.



  1. pax, 22. May 2014, 12:30

    Perhaps the budget failure on trolleybus maintenance is another symptom of the over-arching maintenance debacle. The operators appear to have neither budget nor clue to keep diesel or trolley buses running. The trolley buses die expensively when it rains.

    GW should closely examine the maintenance of the waterproofing on the trolley bus electronics, before NZ Bus advertise for a new fleet and engineering managers.

  2. Daran Ponter, 24. May 2014, 21:42

    Good article Kerry. Let’s hope the NZTA read this!

  3. Cr Paul Bruce, 25. May 2014, 9:29

    There are indeed a number of performance problems with the Trolley buses, but apart from the upgrade of the overhead lines (70% completed), they have not been addressed. It is pure laziness and lack of acumen to then call for their scrapping.

    The silver lining, is that we are now really aware of the considerable expertise held in Zero Emission Vehicles
    and linkage with Kapiti Clean Tech Centre,
    which could be utilised in modernising the Trolley Buses. ZEV have made a submission to the Public Transport Plan Hearing committee ( to be heard on Wednesday 28th May or Thursday 29th May).

  4. Mark W, 26. May 2014, 22:23

    If the GWRC & Go Wellington weren’t being so cheap and actually invested in brand new trolleybuses from either the US, Europe or even China then we wouldn’t have the current problem of the trolleys continuously breaking down.

    As it stands the current trolleybuses aren’t new but are a mixed bag of bastardised parts from the old Volvos chucked on a new chassis with the old electrics. You can even see the old Volvos’ axles.

    It seems that the anti trolleybus brigade at the GWRC have already made up their minds to scrap them in favour of more diesels.

  5. Daran Ponter, 27. May 2014, 17:46

    So, Cr Bruce, you’re a third term regional councillor. It’s all very well to say this is pure laziness to call for the scrapping of the trolleys. You must have a hand in this.

    Why have you not been pushing harder for the trolley upgrades, and if those upgrades do come, who pays for them?

    I’m all for the trolley buses, but you also need to be explaining how you are going to pay for things Paul, and that explanation needs to stack up with the NZTA, who are ultimately whipping the GWRC on this matter.

  6. Daran Ponter, 27. May 2014, 17:53

    @ Mark W – it would indeed be sad if the GWRC had predetermined a 100% diesel bus future.

    There are three funders for public transport – GWRC (via your rates), NZTA (via your taxes) and your bus fare. I would suggest that GWRC are being pressured on the trolley buses by NZTA, who want an explanation as to why it costs more to run buses in Wellington than in other centres.

    If you want a change of approach you effectively need a change of culture and direction at NZTA. If you want that then …..well election day is the 20 September.

  7. Cr Paul Bruce, 27. May 2014, 22:16

    Yes Daran, I do blame myself a little for not attempting to understand some of the issues earlier on. However, you will also know how hard it is to separate fact, rumour and misrepresentations, especially given the complicated ownership of the overhead wires, substations and the makeup of the trolleys themselves.

    The great thing about the submission process and the publicity that has been generated around the scrapping of the trolley buses, is the considerable number of “expert” submissions that we have now received. They are all well worth reading, though there are still a number of issues that still need more investigation.

    The one certainty is that the trolley and overhead wiring have considerable option value, and we will pay dearly if we choose to discard that.

  8. Alana, 27. May 2014, 23:08

    Well said, Daran. Looking forward to election day. I hope the change is for more public transport and not more billions on roads that will remain underused 20 hours of the day.
    Studies in LA have shown the link between diesel and cancer.
    The trolley buses run well most of the time. I’ve seen problems with trolleys three times – the hooks coming off the lines – and heaps more than that with breakdowns with the regular buses.
    The trolleys run more quietly – but the brakes do seem very loud.

  9. Maximus, 29. May 2014, 16:06

    Kerry: a question. Seems to me that part of the issue with the trolley buses is that they have to have 2 wires, and have to have grooved thingees to slide over those 2 wires. Whereas, electric power to trains only has a single pentagraph, which telescopes up to the wire, and can contact it over a much wider surface. As far as I know, the train does not transmit the electricity through the train and into the tracks through the wheels, but instead just makes do with one point of (electrical) contact per train. So, question is: why can’t we / why don’t we do that with trolley buses? Surely we could get a smoother quicker system with half the amount of wires, and virtually no chance of coming off the tracks? The answer is so obvious that i must be doing something wrong with my thinking. Can you help?

  10. Mark W, 30. May 2014, 14:32

    It doesn’t take a rocket scientist to realise that having a pentagraph on a bus is a stupid idea. The trolley poles allow for the ability to move and allow the bus to overtake other vehicles – can’t exactly do that with a pentagraph.

  11. Mike, 30. May 2014, 16:29

    In the absence of a response by Kerry to Maximus: electricity has to have a complete circuit to function. On a trolleybus the electrical supply and return are through the two overhead wires. On a train, supply is generally through a single overhead wire (sometimes a third rail), the return through the running rails, through the wheels to the track.

    So, in the absence of steel wheels and rails, a trolleybus needs two wires.

    But in response to Mark W, Volvo (I think) has tested electric trucks with two pantographs – there’s a video on the net somewhere. Not such a stupid idea after all!

  12. Maximus, 31. May 2014, 9:46

    Mark W – thank you for your helpful comment. You are correct, I am not a scientist of rockets. I believe it is important to question Why things are as they are, and if they need to always stay that way.

    Mike – thank you also for pointing out that it is not necessarily a stupid idea. With the advances in battery technology we are seeing, asking a bus to go all day long solely on battery power would seem to be a big ask, and recharge time might be considerable. But having a pair of automatically retractable pantographs that could rise to power a bus along the straights, and lower when needed to negotiate junctions etc, could be a simple means of having it both ways, speeding buses, and cutting clutter. Glad to hear that Volvo is already thinking along those lines.

  13. Kerry Wood, 31. May 2014, 21:58

    Thanks Mike
    There are some interesting trolley bus ideas around, including:
    Automatic re-wiring;
    Pantographs (with a split collector bar for positive and negative) which sense special charging rails at stops;
    Supercapacitors which can accept a very high charge rate, to top up at stops;
    Lithium batteries (of course) sometimes charged on the move by a supercapacitor – or trolley wires

  14. Daran Ponter, 31. May 2014, 22:15

    Cr Bruce – While it is good that the Regional Council benefits from the views of expert submitters,I would suggest that NZTA should also be receiving these.

    It is after all NZTA who are putting the squeeze on the Regional Council with respect to the trolley buses. And the Regional Council does not have a particularly good track record in standing up to the NZTA (reference fare box recovery rules, Basin Reserve Flyover etc).

  15. Kerry Wood, 1. June 2014, 11:21

    Mark W says the current trolleybuses aren’t new but are a mixed bag of bastardised parts from the old Volvos chucked on a new chassis with the old electrics. You can even see the old Volvos’ axles.
    What are the bastardised parts? I understand them to be
    – Drive axle, which should be OK: they last a long time, and could be overhauled if need be. If they are a problem, the trolleys could use new standard axles, with a standard drive shaft from the motor.
    – Motor. Needs replacement because it is inefficient and to an obsolete voltage.
    – Motor control system. Also needs replacing
    Trolleys should be simple to maintain, so if they keep breaking down, something is wrong. Water in the control system sounds plausible, but what else? What about the trolley poles? I understand that trolley heads may weight 8 kg or 4 kg, and the difference will matter.


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