Some plants love tarmac, especially on small roads. This is the case for this spurge, Spotted Sandmat (Euphorbia maculata). It flattens itself on the surface of the road and covers it with many small stems.
It is not true all Spurges look alike, in fact the Euphorbiaceae family is very diverse with species you would not consider Spurges at all, at first sight. In France there are only two groups of the genus Euphorbia: the green-yellow ones that generally hold themselves upright, and the green-reddish ones that are more spreading. Spotted Sandmat belongs to the last group.
The leaves have sometimes ted spots. It is easy to recognize the fruits as those of a Spurge, little hanging balls. With Spotted Sandmat they are covered with white silky hairs.
You think to see white flowers, but no, they are not real flowers, but white appendices to the glands. The real flowers, small and greenish, are inside those glands and not visible in the picture.
Spotted Sandmat is an introduced species originally from North America and now it grows everywhere in Perigord.