Use of “silent” asphalt would reduce road noise and dust

Possible calls for shorter period when studded tyres may be used

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The road noise and dust troubling Helsinki residents would be reduced if the streets were surfaced with so-called "silent" asphalt. This was the finding of a group of experts commissioned by the Ministry of Transport and Communications to look into the effects of street surfacings and studded winter tyres.
      Also from the point of view of traffic safety the silent street surfacings are better, as their friction properties are better than normal. When braking, the distance to bring a car to a halt is significantly shorter than on ordinary asphalt.
      However, changing the surface material would not reduce road noise caused by studded winter tyres. The silent surface is constructed with more fine-grained rock material than ordinary asphalt and is therefore smoother.
     
"The next thing to consider is the shortening of period for the compulsory use of winter tyres in Southern Finland. From the environmental point of view this would be great, but it must not happen at the expense of traffic safety", says traffic counsellor Risto Saari from the Ministry of Transport and Communications.
      Saari hopes that the ministry will look into the matter. No decisions have been made yet, but discussion of a more lenient attitude towards the compulsory use of winter tyres seems somewhat topical. All one needs to do is take a look out the window on a rainy mid-winter day! Studded tyres under the current conditions will do little to improve grip, and they are a serious problem both in breaking up road surfaces, causing rutting, and in generating dust particles.
     
"The compulsory time for winter tyres could, for example, start in mid-December before the holiday season, and end earlier in the spring", Saari ponders. At present the winter tyre season may continue well into April, depending on where Easter falls in the calendar.
      The leader of the conducted rolling noise study, project manager Heikki Tervahattu, suggests that the use of studded tyres could be reduced by imposing a tax on them. In the large cities of Norway, raised road tolls are levied from users of studded tyres.
     
"Quality costs money. This applies to asphalt as well as tyres", Saari summarises the conclusion of the Ministry’s road noise study.
      The study found that the noise created by new studded tyres can be up to nine decibels higher than that of friction tyres. In time the wearing out of the studs will significantly lessen the difference, though.
      During the dusty spring months, however, friction tyres actually prove more harmful than studded tyres, as they kick up more dust from the street surface into the air. This is due to their so-called suction cup effect.
      Hence the sensible thing to do would be to switch the friction tyres to summer tyres as quickly as possible in the spring.
      Studded tyres, in turn, wear out street surfaces and produce more dust than friction tyres, which further complicates the dust problem.
     
In Helsinki silent asphalt is tested on one or two streets per year.
      Nearly half of the residents of the capital live in areas that are designated as noisy.
      A national objective is to reduce the number of people living in areas with over 55 decibels of noise by a fifth by the year 2020.


Previously in HS International Edition:
  Helsinki under pressure from EU again over airborne dust (9.12.2005)

Helsingin Sanomat