Wellington Scoop

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The Wellington Regional Council has seen trolley buses as costly and outdated, and has even asked on the consultation form … how do you think the additional costs should be paid for?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 http://www.youtube.com/watch?v=sLOjC8EWrHA

• 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 comment:

  1. David Kenneth Myers, 7. January 2016, 5:29

    What smart thinking. I couldn’t agree with you more. This looks absolutely optimistic in upgrading a trolleybus as it should extend its lifespan for at least another fifteen to twenty years, because we all need to bear in mind that an electric motor has fewer moving parts than an internal combustion powered vehicle ,resulting in twenty five per cent less servicing required.