Apart from shrines on the roads there are also sites with religious symbols to commemorate victims of accidents. Such sites are usually marked with a simple cross, not too high, sometimes with a plaque. They are not graves, of course. According to Polish law, putting anything like that on the side of the road requires a permission from the road maintenance service. But permissions are not given.... So, practically, all those crosses are illegal. But the road services are tolerant and don`t remove them.