It has been used in parking spaces for apartment blocks since at least 1970s in former Yugoslavia: https://m.facebook.com/photo.php?fbid=10153127031260943&id=26

It has been used in parking spaces for apartment blocks since at least 1970s in former Yugoslavia: https://m.facebook.com/photo.php?fbid=10153127031260943&id=265072550942&set=a.323633595942&locale2=sr_RS&refid=13&__tn__=%2B%3D https://m.facebook.com/photo.php?fbid=10153127031260943&id=2... There is nothing particularly worrisome about them, except that it doesn't really grow much grass if frequently used.