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'LITEBUS' – the bus that bounced

LITEBUS, an EU-funded project set to reduce the weight and production costs of urban public transport, has developed a sandwich composite material to replace both steel and aluminium frames for buses. The composite renders the vehicles safer and more eco-friendly.

LITEBUS test rig © LITEBUS
LITEBUS test rig
© LITEBUS

Over 20% of all carbon emissions in Europe are generated by road vehicles. Developing new technologies and materials to shape and assemble vehicles is essential to mitigate the impact of pollution. These materials will also need to render the vehicles safer and offer far greater passenger protection in case of accidents.

“Rollovers only account for 6% of bus accident but this 6% accounts for 40% of the serious injuries,” says LITEBUS Project Coordinator Professor Antonio Augusto Fernandes of the University of Porto. "This is why countries are now imposing new standards for rollover tests according to regulations developed by the United Nations."

Cars continue to dominate our highways and most of our cities, but there is a real push to shift everyday transport from private individual cars to public service vehicles (PSV) such as buses and coaches. One of the main goals of the EU White Paper on European Transport Policy for 2010 is to get more people to use public transport. PSVs are therefore set to play an increasing role in meeting the EU’s stringent 30% emissions reductions in 2010, set against 1995 technologies.

Stronger and Lighter

To meet that demand, LITEBUS has developed an all sandwich composite material that not only reduces weight but also renders PSVs tougher and less prone to structural damage in accidents. A consortium of 13 international partners including industry experts, research institutions, universities and manufactures were involved.

“Another successful EU project,” says European Commission Project Coordinator William Bird. "LITEBUS had generated a new design architecture and development methodologies to reduce emissions, save energy and put into public service high quality urban transport."

Lighter vehicles mean less fuel burned and less carbon emitted. A typical intercity bus weighs around 2000 kg. The LITEBUS sandwich composite material would replace the steel and aluminium alloy frames that are typically used to build the vehicle's body. Thus the overall total unladen weight of a typical bus can be reduced by up to 10% when using the LITEBUS concept.  

William Bird © ZAG
William Bird
© ZAG

“In a preliminary life-cycle analysis we estimate that sandwich composite buses, within a 15 year period, would equal to €30.000 in fuel consumption savings when compared to buses with steel structures,” says Professor Fernandes. Noise, generally emitted from vibrating steel bodies, will also be reduced, making the ride more enjoyable for passengers.

LITEBUS’s structurally resistant composite material would completely revamp how the PSV is manufactured and built. A streamlined production line reduces manufacture costs and saves energy. The composite material is sandwiched into single large panels, reinforced, and easily assembled. These panels would also be load bearing, simple to dismantle, and completely recyclable. They also resist corrosion far better than steel. Current traditional structures consist of hollow sections lined with metallic sheets whereas LITEBUS composite material would make up the entire body in single large sections. The composite panels have the added advantage of making the bus more aerodynamic.

The Test

To demonstrate the material’s strength and flexibility, LITEBUS rolled a section of a bus made with its panels at its site in Madrid (watch the  videoexternal link). Under normal circumstances, a bus with a steel or aluminum body would suffer severe structural damage that could potentially endanger the lives of the passengers. But only the outer skin of a window was broken as the LITEBUS bus smashed and then bounced twice onto the hard concrete tarmac. The structure remained intact. “The test was carried out the day before the project finished - indicating what faith the consortium had in their results,” says Bird, who was present at the test.

LITEBUS was also faced with the challenge of making a material that would be more cost effective and easier to fabricate than steel body parts. Manufactures would need an added incentive to replace the traditional steel and aluminium structures. LITEBUS therefore devised a design methodology to cut expenses that should reduce production lead time for manufacturers by 30%.

Getting sandwich composite materials off the line and onto a vehicle would require using fewer components that are easier and more rapid to assemble than steel. Composite panels, for one, do not require expensive welding techniques. The exterior and interior faces of the panels have better finishes than traditional steel panels and this makes painting them easier.

A Success

LITEBUS set out to meet some tough objectives. And it accomplished them. The roll-over test in Madrid officially closed the project and the bus that bounced has proven the viability of sandwich composite materials.

But sandwiched composites are not necessarily limited to PSVs. The assembly methodologies are also applicable to other industry sectors like rail and maritime transport, opening up a whole range of possibilities to make smarter, greener, and safer vehicles for developed and developing countries.

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