Any permit granted by the director of public service and safety or his duly authorized representative pursuant to this chapter may be revoked and terminated by him at any time when, in his opinion, the terms of this chapter are being violated, or when the continued exercise of the privilege constitutes a menace to the public safety, or is an unreasonable use of the public streets or ways.
('59 Code, § 901.05) Penalty, see § 92.99