In Scotland you can ask a council for permission as per the Roads SCotland ACt. S51.
“The roads authority may in writing authorise an owner or occupier of land adjoining a public road, or any other person, to plant or maintain trees, shrubs, grass or other plants within, or partly within, the boundaries of that road subject to such conditions as the authority may specify in the authorisation.”
If there is similar provisions in England ask the council then plant some sort of 3 ft high shrub. Big enough nobody will drive over it and small enough not to block sightlines.