The powers of a public gas supplier under paragraph 1 above shall include power to erect in any street one or more structures for housing any apparatus, but only with the consent, which shall not be unreasonably withheld, of the highway authority.

Any question whether or not consent to the erection of such a structure is unreasonably withheld shall be determined by a single arbitrator to be appointed by the parties or, in default of agreement, appointed by the Director.

For the purposes of this paragraph the withholding of consent shall, to the extent that it is based on the ground that the structure ought to be erected elsewhere than in a street, be treated as unreasonable if the supplier shows either that there is no reasonably practicable alternative to erecting it in a street, or that all such alternatives would, on the balance of probabilities, involve greater danger to life or property.