Ahh, good old Crownvetch.
According to the University of Missouri Extension:
“Crownvetch is particularly adapted to road bank stabilization and erosion control. At the present time this seems to be one of the best uses for the plant.”
On the other hand, according to the Missouri Department of Conservation Vegetation Management Manual:
“Crown vetch is a serious management threat to natural areas due to its seeding ability and rapid vegetative spreading by rhizomes. This aggressive exotic is now widespread along roadsides, from where it may become a serious invader of Missouri’s natural areas.”