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1HE CURRENT research programme into quiet heavy vehicles should be
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extended, according to a report published by the Transport and Road Research Laboratory, and should cover the noises from vehicles of other categories, including light vehicles of less than 1.5 tons.
The report contains a theoretical study on traffic noise which points out that the rate at which quiet vehicles are introduced will significantly affect the rate at which traffic noise levels are reduced. It may be 10 years before all present heavy vehicles on the roads can be replaced by quiet ones, says the report, but it is estimated that there will be little benefit in traffic noise levels until at least 50 per cent of the heavy vehicles are "quiet". , Predictions are given for when heavy lorries alone are quietened by 10dBA (which is the target of the present programme), when light vehicles alone are quietened by 5dBA (which is assumed to be feasible) and when both categories are simultaneously reduced.
The report concludes that although quietening lorries by 10 dBA should bring considerable benefits on heavily trafficked trunk roads and motorways where there is a high proporticn of lorries (20 per cent or more). Reducing the noise levels of light vehicles would produce most benefit in low-flow situations.
The report, L R624, is obtainable from the Director, TRRL, Crowthorne, Berks.