The appeals board shall grant the permit if any of the following are true:
(a) That the property of which the mapped highway location is a part is of such nature that the owner of the land will be substantially damaged by the refusal to grant the permit.
(b) That the property will not earn a fair return on the owner’s investment unless the construction involved is authorized.
(c) That, balancing the interests of the public in preserving the integrity of the officially mapped highway against the interest of the owner of the land in using his property, the granting of the permit is required by considerations of justice and equity.
(Added by Stats. 1947, Ch. 1451.)