New Roads and Street Works Act 1991

136 Liability for cost of use of alternative route

(1) Where by reason of road works the use of a road is restricted or prohibited and the diverted traffic uses as an alternative route a road of a lower classification, the undertaker shall indemnify the roads authority for the latter road in respect of costs reasonably incurred by them—

(a) in strengthening the road, so far as that is done with a view to and is necessary for the purposes of its use by the diverted traffic; or

(b) in making good any damage to the road occurring in consequence of the use by it of the diverted traffic.

(2) For this purpose the order of classification of roads, from higher to lower, is as follows:

1	Trunk roads.
2	Principal roads.
3	Other classified roads.
4	Other roads.

(3) In this section, “trunk road” and “classified road” have the meanings given by section 151 of the [1984 c. 54.] Roads (Scotland) Act 1984 and “principal road” refers to a road classified as such by the Secretary of State under section 11 of that Act.