Are German Roads as quiet as German Cars?

On our last stops in Europe, the CP Tech Center visited 6 sites in Germany. Two of these sites are of particular interest as they allowed for a "side-by-side" comparison of various concrete pavement texturing techniques. These sites include low-noise pavement test sections on the B56 near Düren and on the A4 near Röhe. If you haven't been to either place, click on the images below for a free tour:

GE02 (B56-Düren) --- GE05 (A4-Röhe)

On Site GE02, we tested 4 unique textures / sections (click on small images to expand):

• Section A - Exposed Aggregate - CRCP
• Section B - Exposed Aggregate - JCP
• Section C - Diamond Grinding
• Section D - Broom Drag

The results for the levels and spectra from the OBSI measurements are as follows (click on image to expand):

Of particular interest on all of the European test sections has been the contribution of the joint "slap" to the overall levels (and to some degree, the corresponding bias in the average spectra). Since all of the measurements were recorded for subsequent postprocessing, the effects of the joints can be seperated from that of the texture. To illustrate the significance, the following plot shows a trace of the average (overall) OBSI level of Section D. In this plot, you will note the quieter "texture" level that is periodically interrupted by a "slap" event at the joint (in this case, every 5m). For clarity, the gridlines have been lined up at the approximate joint locations:

(Click on the above image or HERE to expand)

Meanwhile, on the A4, three different textures were evaluated, as follows (click on images to expand detail):

• Section A - Exposed Aggregate (5mm Nominal)
• Section B - Exposed Aggregate (8mm Nominal)
• Section C - Burlap Drag

At the time of testing, Sections A and B were approximately 7.5 years old, and Section C was constructed 6.5 years ago. The levels and spectra for these three sections can be found here (click on the images to expand):

The project team would like to thank the Bundesanstalt für Straßenwesen (BASt) for their very generous assistance during this effort, especially that of Dr. Igor Müller, Mr. Stefan Höller, and Mses. Beata Krieger and Nina Sliwa.