Also, the road surface has fewer sharp edges which tends to reduce noise. The TRL has also determined which components of surface texture help to reduce tyre vibration while ensuring a good degree of antiskidding performance and hence safety. A whole range of new surfaces with these characteristics have been developed and are now in use on roads. As well as looking at road surface design, the government believes that tyre tread patterns can be modified to reduce noise levels while maintaining safety levels and is thus supporting further research in collaboration with industry. Test methods are also being developed to allow different road surfaces and tyre designs to be compared in terms of their noise performance.
Speed is also a factor in tyre noise generation.
Speed limits have recently been imposed on some German autobahns to help to reduce noise in residential areas. Speed controls on Britain's M25 motorway around London have improved the flow of traffic and consequently reduced air pollution, but have had a less noticeable effect on noise levels. Ongoing research will also investigate the possibility that reduced tyre noise leads to lower rolling resistance and improved fuel consumption. However, the benefits may be difficult to measure because other forms of resistance such as aerodynamic drag are more significant. More information about the TRL's work on quieter road surfaces can be found on the environment pages of the TRL website.