Vacancies in positions in the competitive class shall be filled by promotions from among persons holding positions in a lower grade in the bureau of police. Promotions shall be based upon merit to be ascertained by tests to be provided by the civil service commission and upon the superior qualifications of the person to be promoted as shown by his previous service and experience. The civil service commission shall maintain a list of those persons qualified for promotion to the next superior position, from which list the director of the department of public safety shall make all promotions from among the first four names appearing on the list at the time the promotion is to be made. The civil service commission shall have the power to determine in each instance whether an increase in salary constitutes a promotion.

Any person taking a competitive examination for promotion in the competitive class in the bureau of police shall, upon request, be permitted after such examination to see his examination papers and to review his answers with those who conducted the examination.