The safety board, pursuant to rule, may grant exceptions and variances from the requirements of rules adopted for any conveyance. Exceptions or variations shall be reasonably related to the age of the conveyance, and may be conditioned upon a repair or modification of the conveyance deemed necessary by the safety board to assure reasonable safety. However, an exception or variance shall not be granted except to prevent undue hardship. Such conveyances shall be subject to orders issued pursuant to section 89A.10.