The charge for transportation shall be not exceeding eight cents (8¢) per one hundred pounds (100 lbs.) on heavy articles, and three cents (3¢) per cubic foot on articles of measurement, per mile, and at the same rate for each fraction of a mile, and not exceeding fifty cents (50¢) per mile for each passenger, and at the same rate for each fraction of a mile, with power to make special contracts with shippers and passengers on their roads in regard to rates of freight, and so as not to exceed the amounts herein designated.