When the highways are covered with snow or ice, the operator of any school bus shall not transport school children upon any of the highways of this State unless all rear wheels are equipped with tires having treads designed for use in snow, which tires must be in such condition as to serve the purpose for which they are designed. Any person violating this section shall be fined not less than $10 nor more than $100, or imprisoned not more than 10 days or both.