Section 1. In all counties in this State having a population of five hundred thousand (500,000) or more according to the last preceding Federal Census, or any future Federal Census, the County School Trustees may provide for the purchase and maintenance of an automobile for the use of the County Superintendent. In lieu of providing for the purchase and maintenance of such automobile, the County School Trustees may, in their discretion, allow to the County Superintendent out of the County equalization fund such sum of money per month as will in their judgment cover the cost of an automobile and the expenses of maintaining it, including depreciation thereon, provided that such sum so fixed shall not exceed the sum of One Hundred Dollars ($100) per month. Such allowance, when fixed by the County School Trustees, shall be paid monthly from the County equalization fund. Provided, however, that nothing herein contained shall be construed as authorizing any increase in any tax rate now in effect in any such counties.