Dear Flavio, I haven't found any literature about this topic, yet. In my opinion it is difficult to determine what the effect of roughness alone on the backscattering signal is. This has several reasons: 1) the texture is usally finer than the SAR wavelenght 2) The uneveness of roads has probably a stronger effect than roughness 3) The same is for the asphalt composition. A high share of tar will cause probably different backscatter effects than a low share 4) The exposition of the road segment.... and so on.

But anyhow, I would be interested if you find suitable study areas to determine the effects.

Dear Sir,

Pl find attachment. I hope it helpful for your research work.

All the best

http://www.ijte.ir/pdf_2631_65ed482b5e1fbb62d50e7e8a96ac5a4d.html

1. Is there relationship between asphalt roughness and SAR backscattering coefficients?

A. Obviously. But results will be severely biased by car traffic, off-road infrastructure (road signs, poles, ads), trees (remember all RS radars are backscattering radars), buildings, hills and mountains, etc.