A rubbery solution to road noise complaints

PUBLISHED : Monday, 16 July, 2007, 12:00am
UPDATED : Monday, 16 July, 2007, 12:00am

New surface material helps reduce decibels

A new material could be the solution to the problem of Hong Kong's traffic noise - created by adding rubber to the asphalt and gravel used to resurface roads.

Rubber helps to absorb noise and the government is considering using this material - already used in the United States - to benefit residents who live alongside noisy roads and do not want their views blocked by noise barriers.

If the material is deemed suitable, it will be used to resurface 26 roads, mostly in urban areas such as Mong Kok, Yau Ma Tei and Tsim Sha Tsui.

The government says the programme would cost about HK$46 million, with an annual maintenance cost of about HK$7.5 million.

It estimates 70,000 residents could benefit from the programme by 2010.

According to a noise study released by the government last year, about 1.1 million people are exposed to road traffic noise exceeding 70 decibels (dB) when at home. It estimated the number of people exposed to that level of noise would reach 1.2 million by 2016.

Existing solutions involve mixing gravel in the asphalt and building noise barriers.

Last year 72 roads were chosen for a resurfacing programme using the gravel mixture, a technique introduced from Britain in 1987.

Elvis Au Wai-kwong, assistant director of the Environmental Protection Department, said based on the 30 roads on which resurfacing had been completed, the gravel mixture reduced the noise level by only 3 dB. Noise barriers reduce the noise level by 5 dB, but residents complain of blocked views.

The department is now studying the performance and cost of two materials, one used in the US and the other in the Netherlands, which reduce the noise level by 5 dB.

The Arizona transport department in the US has been adding rubber cubes to paving material to enhance noise absorption since 1988. In the Netherlands, roads became more porous when they were resurfaced with smaller gravel.

Mr Au said the US method was better because the rubber mixed into the paving material came from old tyres, which also benefited the tyre-recycling industry.

But he said further tests had to be conducted to see if it could be used locally.

'The road usage in Hong Kong is very different from overseas,' Mr Au said, adding that the high usage of roads might undermine the durability of low-noise materials.

For example, if more than 37,000 vehicles use a road every day and more than half are heavy trucks, the road is not suitable for the resurfacing programme.

Chow Ka-kong, a district councillor representing City One in Sha Tin, urged the government to resurface Ngan Shing Street as soon as possible.

Residents have been annoyed by heavy vehicles at night for more than 20 years but worried noise barriers would be an eyesore at lower levels.

Aural relief

By adding rubber to asphalt, the Arizona transport department found the noise level of a road dropped by 5dB