MODELLING OF ACOUSTICAL ROAD SURFACE CHARACTERISTICS WITH RODAS (ROAD DESIGN ACOUSTIC SIMULATION)

The potential to reduce tyre-road noise is an important performance characteristic of modern road surfaces. This characteristic is, however, in many cases conflicting with other surface characteristics like skid resistance, wet grip and sensitivity to iciness. In order to optimise the integral performance of road surfaces, it is important to be able to control a number of fundamental physical surface characteristics like the texture, the porosity and the flow resistance (for water and air) of porous layers. Unfortunately these characteristics cannot be controlled in a direct way by choosing the material properties of the pavement mixture. Nevertheless an explicit relationship must exist between the material properties of the pavement and these surface characteristics. The simulation model RODAS (ROad Design Acoustic Simulation) has been developed to predict the physical characteristics (texture profile, porosity, specific flow resistance and acoustical structure factor) from the civil engineering specifications of the pavement mixture (distribution of aggregate particle dimensions [i.e. the sieve grading curve of chippings], chipping shape, amount and type of binder, percentage of sand and filler). It is primarily designed as a separate module of the integral tyre-road noise interaction model TRIAS (Tyre Road Interaction Acoustic Simulation), with the purpose of feeding the road surface properties into the computations. This module can be used independently and has been validated against a variety of measurement data. It has proven to be a useful tool in the early stages of road surface design. This paper presents the set-up of the simulation model, its theoretical basis, the results of the validation and the possibilities and limitations of its application. For the covering abstract see ITRD E122374.