Trolleybuses in the future
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With constant financial pressure to demonstrate 'value for money' and an assumption of 'green credentials', the latest public road transport projects have been moving toward electric traction and rubber tyres. And with less than successful fuel cell or even hybrid buses, thoughts are moving toward a more straight forward solution, one that does away with on-board electricity generation altogether, but does add overhead wiring - the electric trolleybus. The great advantage, shared with trams, is good efficiency, 100% zero emissions at street level and, if powered renewably, no emissions throughout the system. Users consistently like the near silence and the smooth ride - just ask passengers in Arnhem (the nearest system to the UK) what they think of any thoughts of substitution and you'll be met with outrage.
Seen but not heard
Some places have never lost faith. Shanghai has been continuously operating trolleybuses for over 90 years. Moscow has nearly 2,000 in daily service. Rome has recently re-introduced them. Philadelphia, Riga and Milan have renewed their fleets. And three recent Olympic cities have all replaced or extended their systems to conform to clean air requirements (Athens, Beijing and Vancouver). There are over 40,000 trolleybuses in service throughout the world.
There has been something of a revival of interest in trolleybuses of late because of oil prices, global warming concerns and difficulties with the alternatives. Tram plans, especially in urban areas without great demand, are falling foul of cost constraints. Various 'green' bus technologies are proving either immature, less environmentally effective than planned or more expensive than at first envisioned. It is being realised that for heavily used routes, the trolleybus is certainly worth serious examination. New systems in Spain, Venezuela and Italy are providing real insights into 'new generation' trolleybuses or, as they have been called, with greater legitimacy in some places than others, 'trams on rubber tyres'. Plans for new trolleybus systems include Leeds and Valenciennes, both of which replace tram schemes that are regarded as too expensive.
Nancy's 'Stan' guided trolleybus on the Rue Saint-Jean. Photo - Liom
To guide or not to guide
The re-think has to do with overcoming, in this country at least, perceptions of the technology being somehow 'outmoded' as no trolleybus has run in public service in the UK for nearly 40 years. The reality is that world wide trolleybus technology has kept pace with tram developments, by sharing the same electrical control packages, and with bus developments, including bi-articulation and low floors, where trolleybuses can, with hub motors, achieve completely low level floors and wide aisles. Swiss overhead wiring design has considerably reduced visual impact and greatly increased collection reliability. Off-wire ability has become standard, using small diesel units or more recently, improved traction batteries to sustain service in areas regarded as sensitive to wiring intrusion - the Rome system uses trolleybuses with Toyota Prius battery packs that power the vehicles over a 3 km central section of the route in the city centre. The 'stepchild' of bus and tram technologies has spawned systems that are guided. French initiatives in Nancy, Caen and Clermont-Ferrand use rubber tyred bi-articulated vehicles that use a central rail as guidance. Bologna, in Italy, is taking delivery of 49 Irisbus/Iveco Civis trolleybuses that use Siemens optical guidance over a 19km network of 4 routes which is due to open in 2009. A similar system recently opened in Castellon, Spain, the first stage of an extensive network. The claimed advantages of the 'Optiguide' system are the ability to automatically dock at curved stops with a better than 50mm gap at the platform and to maintain higher speeds on very narrow corridors. But most development has been without innovative additions. Trolleybus Rapid Transit schemes, using segregated roadways without guidance, have proliferated since the pioneer system in Quito, Ecuador demonstrated the ability of trolleybuses to move over 250,000 passengers a day over a 11.2km route. Its great success led to extensions to the system and emulation at Merida and Barquisimeto in Venezuela. These networks are true alternatives to trams at lower cost, with architecturally impressive 'stations' on the Merida system that would do justice to the most prestigious railway!
The Trolmerido's Terminal Ejido served by trolleybuses running on dedicated roadways. Photo - Geraldo S�nchez
At the end of Oil
A recent book "Transport Revolutions - Moving people and freight without oil" (Earthscan 2008) by Richard Gilbert and Anthony Perl, suggests that after oil production peaks in 2012, one of the most crucial developments will be the extension of trolleybus technology to provide widespread replacement of existing diesel and petrol based transport in both moving people and freight in both the urban and inter-urban situations. Their analysis is based on practical alternatives to oil, in the context of battery and fuel cell technologies remaining physical challenges that will be difficult to consider for global implementation. Electrical power storage systems should be seen as adjuncts to the core system of direct power transmission through overhead wiring. In other words, devices such as supercapacitors provide an excellent way of maximising the use of regenerated power caused by braking, but are unlikely to substitute for the robust simplicity of power collection through trolley booms. Tests on a trolleybus fitted with supercapacitors in Solingen, have shown a reduction in power consumption from 2.4 euros/km to 1.8 euros/km. The components have the advantage over batteries of a million recharge/discharge cycles and a life of 15 years. Batteries used on trolleybuses in Rome, to provide running without overhead wiring, are showing a life of about 4 years.
Why the wires?
The perceived need to avoid overhead wiring, for trams as well as trolleybuses, remains a force to develop improved versions of technologies that can provide it. Apart from fuel cell and battery research and development, two companies are suggesting power supply via magnetic induction. Bombardier proposes continuous induction with its "Primove" system using iron plates attached to the underneath of the vehicles, 70mm from underground cabling and with storage in supercapcitors. The system is claimed to provide 250kW continuously, sufficient for a 30m vehicle at 40km/hr, but no claims are yet made for efficiency. It wasn't clear, at a recent presentation, whether trolleybus versions could deviate from the supply in the way they can under overhead wiring to avoid traffic obstacles. A second system, proposed by Numexia, envisions induction power supply only at stops with either battery or supercapacitors taking vehicles between. A trolleybus route in Shanghai has been running supercapacitor buses with extendable pantographs that engage at each stop to recharge the storage devices. After a number of years, the results have been mixed, with doubt that the system is robust enough to cope with high passenger levels. Heavy rainfall has, on occasion, paralyzed the service so trolleybus overhead wiring has been retained on the route. Despite the need for maintenance, trolleybus power supplies can cope with extreme weather, even when diesels can't. The vehicles have also always been able to outperform any other type of PSV on steep gradients. Historically, attempts to replace trolleybus overhead wiring with technologies such as mechanical flywheels or power induction have never led to their widespread adoption.
Alternative fuels, such as CNG have also not seen real adoption, as the advantages remain marginal and infrastructure costs remain a barrier. Hybrid buses, either series or parallel, have been making an increasing appearance in city centres, including, notably, New York. They remain planned for large scale introduction into London. Their use has had to be subsidised, up to 90% in the US, with Federal grants. Operational service results suggest fuel savings of 10% rather than the claimed 20% made by manufacturers. While carcinogenic emissions are reduced, they are still present, when they could be avoided altogether. The added complexity, weight, efficiency losses and cost make hybrids more of a political answer to demands for 'greener' buses rather than being any long term environmental solution. Real greenhouse gas savings achieved by the technology or additional modal shift from car use is likely to be small. Transport authorities have, perhaps, been guilty of making exaggerated claims for hybrids, which the travelling public are unlikely to question, such as their being 'electric' buses with all the connotations of zero emissions and cleanliness when they are in fact, diesel buses with electric drives. The experience of Toronto with hybrids has led to a study that re-examines trolleybuses. It may well be that further oil price shocks, plus wider understanding of energy efficiency, will lead to the realisation that hybrids are at best, an interim solution.
A 25m bi-articulated Zurich Hess 'Lightram' trolleybus. Photo - Hess
But they cost more!
Trolleybus overhead wiring and traction motors can, and do, last for 50 years. The vehicles inherently last longer than diesels - 30 years is becoming an accepted standard in total life cycle costing analysis, borne out by real life experience. A great deal has been made of whether trolleybuses are more expensive than diesels, with no real consensus, except to say they are comparable. Recent figures from Zurich and Luzern would have trolleybuses both cheaper and more expensive, although the Zurich figures don't take into account that all non-identifiable maintenance costs are charged to the trolleybus division! Overhead costs can be offset against much lower maintenance costs and the longer life of the vehicles. With intensive use, at which trolleybuses are adept, the network generates higher income; an assumption that can safely be made with the proven popularity of trolleybuses. In any case, for present day route installations, the cost of real time information systems, proper stop facilities and roadway segregation measures are likely to cost considerably more than the vehicles and their infrastructure.
No technology is a total panacea. And some are seen in subjective rather than objective terms. The trolleybus has suffered from a bias that has seen it as a mongrel caught between trams and buses. Today there is revival that reflects awareness of its inherent practicality as a clean, cost effective mode, capable of shifting more than 10,000 passengers/hr. There has never been a time when passengers haven't appreciated the advantages of trolleybuses. Figures from San Francisco even showed a decrease in patronage of 16% when like-for-like diesels replaced trolleybuses. By the travelling public, wiring has been seen as an obvious quality investment by transit providers to give permanent service over particular, readily identifiable routes. Business leaders understand this to have positive impacts on local economies. As oil prices rise faster than electricity prices, there will be increased investment in electric traction. As the need to reduce greenhouse gas emissions becomes increasingly more obvious and essential, so the trend is likely to be re-enforced. Unless some revolutionary new technology is invented, such as a drastically improved electrical power storage device, the trolleybus could start to replace diesels on core routes. The authorities in Paris are coming to this way of thinking, with an examination of core routes that don't justify laying rails, but do have considerable traffic. In Lyons, the idea of high quality trolleybuses running on partially segregated routes has already been implemented.
A 18m Cristalis trolleybus turns at Cit� Internationale in Lyon on dedicated route C1.
Photo Lyon en Lignes
|A photo montage of a 25m trolleybus operating in Leeds City centre.
Photo - Electric Tbus Group
West Yorkshire PTE (Metro) has faced the depressing cancellation of a 3 route 'Supertram' network with a great deal of work to find an alternative. After commissioning WS Atkins to study the government's proposal to substitute buses, Metro now prefers trolleybuses as the solution. But, for fear of receiving no funding, the planners have to remain, publicly at least, "mode agnostic". The network, forming a core of the highest demand routes and assisting urban regeneration, would include considerable segregation, an ideal situation for trolleybuses. Hurdles to overcome include acceptance of trolleybus technology, commitment to high quality provision as necessary for congestion reduction and allowance for high capacity vehicles - the very best solution would include unprecedented use of bi-articulated trolleybuses. The business case for the scheme will be submitted in spring 2009 for building by 2012.
Short-termism has been a constraint on trolleybus implementation, both as applied to the economics and to providing answers to the environmental crisis we otherwise face. Irrational and increasingly irrelevant objection to overhead wiring is also likely to subside as the adoption of directly powered electric buses take to the streets.
More details of worldwide Tbus developments are here