Polyurethanes: Eliminating noise pollution

A report published by the European Heart Network highlighted some shocking statistics: each year, cardiovascular disease (CVD) causes over 4 million deaths in Europe. It is the main cause for women in all European countries, and is the cause of 47 per cent of all deaths on the continent. The total economic impact of CVD is a staggering €195 billion annually. Yes, that’s ‘B’ for billion.

Another shocking statistic recently unearthed is the fact that one in 50 heart attacks are caused by chronic exposure to loud traffic. According to the World Health Organisation (WHO), about 40 per cent of EU citizens are exposed to road traffic noise at levels exceeding 55 A-weighted decibels (dB(A)) – WHO guidelines recommend less than 30 dB(A) in bedrooms for a “good quality” sleep and less than 35 dB(A) for “good teaching and learning conditions” in classrooms. Though Rock N’ Roll might not be noise pollution, our daily drive to work is actually a widely underestimated health threat to ourselves and others.

Heart disease itself can be combated by any number of activities, including exercise and a heart-healthy diet, but what about traffic? Can we afford to put in place policies that may impact economically vital transport? The latter, according to European Transport Commission Siim Kallas, “is not an option”. What then? Roadside barriers? These are expensive – costing up to $600,000 per kilometre – and often lead to less-than-tasteful graffiti.

A recent article in the Economist, however, highlighted another option: polyurethane.

Experimentally used since the 1960s, adding rubber ‘crumbs’ to the bitumen and crushed stone used to make asphalt has allowed engineers to design “quieter streets”; it keeps the noise down in a couple of ways: adding rubber thickens bitumen, allowing for bigger pores which helps trap and disperse sound waves, and also, due to its flexible and springy nature, can absorb unwanted sonic energy. Rubberised asphalt not only cuts traffic noise by around 25 per cent, but also lasts longer!

PERS, or poro-elastic road surfacing, is also used; it’s a blend of crushed stone, rubber and polyurethane. The latter allows for even bigger pores in the road surface. Though more expensive, tests suggest it can cut traffic noise in half. This, according to research at the Belgian Road Research Centre in Brussels, helps boost property value – and therefore land taxes – which in the end covers the cost.

Not surprisingly, the technology is catching on: more than 32,000 kilometres, or 0.5 per cent, of US streets are re-paved annually using the technique. Rubberised roads have also gained popularity in Europe, especially Spain and Germany, and could spread even further given economic and health benefits.

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