## Road surface texture and rolling noise

Svein Å. Storeheier

SINTEF IKT, Akustikk

7465 Trondheim

Tlf. 73592638 / 92252953

svein.storeheier@sintef.no

Measurements of road surface texture (2D) were carried out on a great number of pavements in Norway during the period of 2006 – 2008. This work was part of the R&D project “Environmentally friendly pavements” run by the Norwegian Public Roads Administration.

This report makes reference to measurement methods and validations that were established in an early phase of the project. Shortly, it summarises the main features of road surface texture, and the technical units involved.

On a selection of 37 asphalt pavements (dense type, age 1 year or more) and 8 new-laid pavements, several investigations were carried out. The main purpose was to increase knowledge concerning:

• Texture in dense road surfaces and its influence in general,

• Investigate - if possible – the relation between texture and noise (by the CPX-method), possibly also some connection between texture and pavement parameters,

• The development of texture in time, especially during the first year of operation,

• Give examples of texture data for common Norwegian dense pavements.

The investigation had some considerable restrictions. It was limited to noise from only one car tyre (the reference tyre A), rolling at only one speed (50 km/h). Further, no porous pavements were included.

The parameters of the pavements (concerning for instance the binder, chipping size, resistance to wear, additions, etc.) were collected.

The texture data included the texture spectrum, and a number of texture related parameters (for instance Mpd, G-factor).

The results showed great variation in texture data from each type of pavement, and also between the pavement types.

The noise levels, texture data and pavement parameters formed a basis for statistical treatment.

A simple regression analysis showed that CPX-noise can be modelled with reasonable accuracy based on measured texture data. The analysis in some cases indicates a connection between texture data and pavement parameters.

The development in texture from new-laid pavements showed a relatively unambiguous pattern. The texture spectrum changes markedly during the first year. This change tends to increase the noise.