Could be Dame's Rocket, or we call them "wild Phlox".

It will be dame's rocket, an invasive plant that takes over and suppresses many spring ephemerals. In southeast Michigan, it's officially a "bad" invasive plant that we are trying to remove. Phlox (even wild phlox) has five petals, whereas dame's rocket has four.

It could also be crown vetch, and invasive legume widely planted on roadsides in years past. It can be white or lavender.

Probably any plant successful enough to be seeded by itself on a roadside is toing to be invasive. I expect mixtures of natives are a better idea.

Paula

Here is a link that might be useful: roadside plantings of crown vetch