One of the most far-sighted elements of the appeal of trolleybuses is their claim to be the lowest carbon option for public transport. But is it really true?

The Canadian government’s environment agency, Environment Canada, compared several forms of road transport. Their report gives greenhouse gas emissions in grammes per kilometre*.

‘Clean’ Diesel Bus: 1966g/km
Diesel/Electric Hybrid: 1581-1725g/km
Trolleybus: 1930g/km

So there’s not much in it, and hybrids appear to be the lower-carbon option.

I must admit to not knowing how Canadian electricity’s carbon emissions compare to the UK’s, but they would have to be substantially worse to make trolleybuses lower carbon than hybrids.

And even attributing trolleybus electricity to the grid average is sleight of hand. Because they replace oil-fuelled buses that make no demands from the grid, trolleybuses add to overall electricity demand. This means more electricity will have to be generated somewhere. The only part of the grid with a large quantity of spare capacity are the coal power stations.

Whilst the averaged-out grid emissions are 480g/kWh, coal is 910g/kWh.

If we are to say that, as will largely the case, the power for trolleybuses will be extra coal generation then their carbon emissions would surely be far worse than the hybrid buses.

Also, the urgency climate change means we should not only choose low-carbon options but the ones we can deploy quickest. The vast infrastructure needed for trolleybuses mean they wouldn’t be on the streets of Leeds for at least six years. Hybrids could be on the road within months.

The trolleybus has the advantage of being ‘decarbonisation-ready’ because as the grid becomes powered by low-carbon sources, the emissions for the trolleybus go down. But as long as coal power stations are the standby that generate for extra demand, trolleybus emissions should be attributed to coal.

A low-carbon grid is a long way off. Hybrid buses – the mandatory design for all new London buses from 2012 – give the advantages of driving in urban areas on electric power so they have no localised emissions.

For the longer term, as renewable electricity supply hopefully becomes significant, electricity is clearly the low-carbon way to power our vehicles. Additionally, in one or two decades time oil prices are likely to be substantially higher than today, making the diesel and diesel-hybrids prohibitively expensive.

But why should we choose trolleybuses even then? At that far-off time, battery electric buses could take over. They have all the low carbon and zero-exhaust advantage, but with infinitely more flexibility. A trolleybus is shackled to its wires, only able to run for very short periods away from them. A battery bus can drive on any paved road. It requires none of the installation and maintenance work of the overhead wires.

Electric vehicles are fixed in the public mind as milk floats, but that is rapidly changing as modern electric vehicles take to the streets. Already we see Tesco and TNT using electric delivery lorries.

Trolleybuses have the advantage of ongoing supply, whereas batteries run out (Tesco cite the 100 mile limit as a reason to favour more hybrids over electric trucks). However there can be no more suitable project for battery vehicles than short-range, timetabled, centrally organised urban public transport.

In the long term we’ll get cheaper and more flexible public transport from battery powered buses at emissions comparable to a trolleybus. In the short term, until a renewables-based grid exists, electric vehicles cause more coal to be burned, making the diesel-hybrid the genuine low-carbon option.

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* Note: this post was first published with erroneous carbon emission figures. This has now been amended and relevant wording rewritten, but the first four follow-on comments refer to the original figures. We thank Irvine Bell for bringing the error to our attention.

NGT’s route through the city centre would demolish stalls at the outdoor market.

NGT’s publicity people say they will be ‘relocated’, which is one of their euphemisms like ‘rationalising’ bus stops. They can’t say where the stalls might be moved to, because there isn’t anywhere for them to go. The stalls will be obliterated.

The stalls under threat are the ones along the back wall nearest the bus station. That is, the ones that sell the cheapest fresh fruit and veg in Leeds. They are a key part of keeping lower income people healthy.

As with cutting down trees to make space for idling traffic in Woodhouse, in the markets we see an attack on the health and wellbeing of those who live in inner Leeds for the benefit of commuters from outside.

If NGT goes ahead it would remove the cycle lanes along Headingley Lane between Headingley Hill and Hyde Park Corner.

NGT’s publicity team defend this by saying that NGT would add more cycle lanes than it takes away.

But it’s no good having cycle lanes in little shreds that disappear just when they’re most needed.

The absence of continuous cycle lanes makes it a dangerous and unappealing option and thereby keeps people in their cars.

To remove any cycle lanes as part of a plan to tackle congestion is absurd.

Leeds City Council and Metro admit that their preferred option for NGT would involve the loss of the avenue of trees between Rampart Road and Clarendon Road, as well as mature trees in Headingley and at Hyde Park Corner.

They say that it’s acceptable because every tree they cut down will be replaced by three others.

But they’d not be replacing like with like.

Mature trees are hosts to a range of wildlife, notably birds, insects and to a lesser degree fungi. The larger the tree the more carbon it sequesters, ie the more oxygen it generates.

Additionally, large trees substantially affect the character of an area.

Councils know all this and have lists of protected trees for many areas, detailing the specific individual trees that you cannot cut down without permission.

If you or I cut down the trees on the Moor and offered saplings in replacement would we get prosecuted rather than praised, and it should be no different for anyone else who does it.

Even if NGT did go for appropriate broadleaf trees, new saplings would take many decades to be any sort of replacement. The wildlife that uses the present trees will have been displaced and the residents of the area will have had more traffic for less oxygen.

Saplings are not a replacement for mature trees any more than apple pips are a replacement for an orchard.