Why the Wires?

The short answer is physics, but to begin at the beginning…

Climate change, polluted air and sustainability are driving development of not just low carbon, but zero carbon buses.

For over a 100 years trolleybuses have been emitting nothing. Right now, there are 40,000+ in service worldwide.

Tried and tested, evolving and improving, trolleybuses are heavy load carriers, essential in the world’s biggest and most polluted cities – Mexico City, Shanghai, Sao Paulo etc.

Some cities see them as essential to a high quality of life, in Zurich, Salzburg and Lyon for example.

And some cities couldn’t function without them, Moscow, San Francisco and Beijing etc.

So why are trolleybuses not sufficiently considered?

The imperative to avoid climate change has assumed a need for ‘new’ technological answers.

The last decade has seen trials, tribulations and hybrids. In the UK the context is state subsidy, short-termism and a certain aversion to overhead wires.

These ‘answers’ are like trolleybuses, but with the booms taken off and various power stations added on. Fuel cell buses are the most complex, hybrids add a polluting diesel generator and battery buses try to store enough electricity.

None of these solutions can ever be as efficient as direct power trolleybuses.

• Having an onboard power station takes space and adds weight. • Hybrids still emit carcinogenic pollutants. • Fuel cells double convert fuel to produce electricity. • Battery buses hit physical limits to stay in service and • need trolleybus like infrastructures to keep going.

• So far, no zero emission bus has been invented that can serve • mainline, heavy duty routes like a trolleybus can.

Only a few more years, and maybe superbatteries will be here. Plus a bit more subsidy and don’t worry about battery replacement costs every four years – roughly doubling bus capital costs every 12 years.

Meanwhile, trolleybuses last twice as long.

The real question is how serious are we about climate change? Or air pollution that kills? We can pretend the physical chemistry of batteries will one day triple in power, or that catalytic converters on hybrids will work in service, or that platinum will suddenly be plentiful.

Or we can save lives now with overhead wires.

Nobody is suggesting trolleybuses should go everywhere.

The future is surely electric, with niches for battery buses, but real routes need real trolleybuses.

Much of the basic technology is shared. And there’s opportunities for better infrastructure efficiencies both for charging and reducing the extent of overhead.

Hybrids are an intermediate technology, coming before full electric buses, but the time is approaching when pollution tolerance and the physical limits of chemistry need to be addressed.

As Luc Tremblay of STM Montreal has said, we’re going to try all the alternative fuels and battery systems and then, to achieve zero emissions, we’ll order 200 trolleybuses in 2020.

Diesel v Hybrid v Trolleybus net emissions, based on conversion of 50% of London bus fleet

(v. trolleybus) (v. trolleybus) (v. diesel) (v. diesel)

Using diesels is not viable long termFuel economy and pollution saving claims for hybrids are proving falseThe promise of autonomous electric buses remains ‘just around the corner’Only the trolleybus can deliver zero pollution at street level reliablyPollution kills, overhead wires do notA fixed infrastructure is appreciated as permanent, high quality transport

• For more, see tbus.org.uk

Quiet and zero emissionSuitable for pedestrianised areasAcceleration means 9 not 10 busesNo refuellingLow maintenanceProven 25 year service lifeWhole life costing pays for overheadDemonstrated customer preference