How M+P helped the Netherlands become a leader in quiet road surfaces (26/50)

For traffic noise pollution, the motto in the Netherlands is: tackle it at the source. After all, noise that is not generated in the first place does not require any extra measures such as noise barriers. Road authorities therefore focus mainly on reducing tyre-road noise. “The interaction between the tyre and the road surface causes most traffic noise,” says Ronald van Loon, senior traffic noise consultant at M+P. “The trick is to change the road surface so that it radiates less noise from car tyres.”

Subsidised research

To stimulate the innovation of quiet road surfaces, the then Ministry of Housing, Spatial Planning and the Environment (Volkshuisvesting, Ruimtelijke Ordening en Milieu, VROM) launched the Silent Road Surface Incentive Scheme in 2001. This reduced financial risks for road authorities when building new quiet roads. In return for the subsidies, municipalities, provinces and water authorities had to measure how quiet the new road surfaces were just after construction as well as in the future. “The ministry wanted to gain insight into the noise emission of quiet road surfaces over a longer period of time,” says Ronald.
Commissioned by the ministry, Ronald and his colleagues therefore drew up the Production of Noise Control (Productie Controle Geluid or PCG in Dutch) measurement protocol. Ronald: “This states, for example, how to perform a measurement, how soon after the construction you should measure, and how often you should repeat it to be able to make statements about acoustic behaviour.”

Measuring methods

According to the PCG protocol, road authorities could choose between two measurement methods. One is the SPB statistical method which uses roadside microphones to measure noise emissions at a single location. The other method has a more personal touch for Ronald. He developed this so-called CPX method for M+P as his graduation project. “In doing so, you can measure the sound with a trailer full of equipment. The advantage is that this allows you to measure not just a part, but the entire section of the road,” says the specialist. “This will give you a much more complete picture of acoustic behaviour in practice.”

Success

The incentive scheme was a success; within a year, the subsidy jar was empty. The result: the number of municipalities and provinces with quiet road surfaces rose from just a few to as many as 50. With more than 150 test plots to be measured and monitored at regular intervals. It earned M+P many commissions. “Any acoustic agency was allowed to perform the measurements, but because of our knowledge and good image, many road authorities came to M+P.”
The funded projects provided many insights. Administrators decided to experiment mainly with thin noise-reducing coatings. Ronald: “These proved to be much more durable than the well-known zoab or double-layer zoab. They quickly became the standard type of quiet road surface within cities and provinces.” The regular monitoring also provided a lot of knowledge which M+P used to fine-tune its calculation models. “Partly thanks to the subsidy scheme and our help with this, the Netherlands is now seen as a leader in the field of quiet road surfaces. Competitors and road builders from all over Europe are eager to work with M+P.”