A highway authority may carry out—
on land acquired by them under section 246 above;
on any other land belonging to them;
on any highway for which they are the highway authority;
on any highway which they have been authorised to improve or construct by virtue of an order under section 14 or 18 above,
works for mitigating any adverse effect which the construction, improvement, existence or use of a highway has or will have on the surroundings of the highway.
Without prejudice to the generality of subsection (1) above, the works that may be carried out under that subsection include the planting of trees, shrubs or plants of any other description and the laying out of any area as grassland.
A highway authority may develop or redevelop any land acquired by them under section 246 above, or any other land belonging to them, for the purpose of improving the surroundings of a highway in any manner which they think desirable by reason of its construction, improvement, existence or use.