(a) For the purpose of improving, maintaining, repairing, constructing and reconstructing the county highways required to be maintained, repaired and constructed by the county as provided in Section 5-401 of this Code, and for the payment of lands, quarries, pits or other deposits of road material required by the county for such purpose, and for acquiring and maintaining machinery and equipment, or for acquiring, maintaining, operating, constructing or reconstructing buildings for housing highway offices, machinery, equipment and materials, used for the construction, repair and maintenance of such highways, the county board shall have the power to levy an annual tax to be known as the "county highway tax". Such tax shall be in addition to the maximum of all other county taxes which the county is now or may hereafter be authorized by statute to levy upon the aggregate valuation of all taxable property within the county. Such "county highway tax" shall not be extended at a rate exceeding .10%, or the rate limit in effect on July 1, 1967, whichever is greater, of the value, as equalized or assessed by the Department of Revenue, of the taxable property within the county, exclusive of the amount necessary to pay the principal of and interest on county road bonds duly authorized before July 1, 1959 for the construction of county highways, unless otherwise authorized by a vote of the people of the county. The county highway tax rate may be increased to .20% as provided in subsection (b). In counties having less than 1,000,000 inhabitants, the amount that may be expended for the purchase of machinery or equipment for constructing or maintaining highways shall not exceed in any one year an amount in excess of 35% of the maximum extension for highway purposes for such year. In counties having 1,000,000 or more inhabitants, taxes levied for any year for the purposes specified in this Section shall be subject to the limitation that they shall not exceed the estimated amount of taxes to be levied for such year for such purpose as determined in accordance with the provisions of Section 6-24001 of the Counties Code and set forth in the annual appropriation bill of such county; and in ascertaining the rate per cent that will produce the amount of any tax levied in any such county under the provisions of this Section, the county clerk shall not add to such tax or rate any sum or amount to cover the loss and cost of collecting such tax. However, the foregoing limitations upon tax rates, insofar as they are applicable to counties of less than 1,000,000 population, may be increased or decreased under the referendum provisions of the General Revenue Law of Illinois. All moneys derived from the "county highway tax" shall be placed in a separate fund to be known as the "county highway fund" and shall be used for no other purpose. In any county containing 1,000,000 or more inhabitants, however, any appropriation or levy to be used for lands, easements and rights-of-way, motor vehicle equipment, mechanical equipment, engineering and drafting equipment, road materials, road, bridge and drainage improvements, grade separation improvements, railroad grade crossing improvements, warehouse and garage improvements, street signs and signals need not be expended during the fiscal year in which the appropriation or levy was made but shall also be available during the following fiscal year without reduction of any levy made during the latter fiscal year. After the end of that latter fiscal year, if there is still an unexpended balance, it shall operate to reduce, in like amount, any subsequent levy. It shall not be a defense or objection to any appropriation or levy made in a subsequent fiscal year for the same purposes that there remain uncommenced or uncompleted projects or unexpended moneys arising in an appropriation or levy of a prior year as contemplated in this Section.(b) The maximum county highway tax rate provided for in subsection (a) may be increased not to exceed .20% if such increase is approved by a majority of the voters of the county voting on the question. The question shall be certified to the proper election officials, who shall submit the question to the voters at an election. Such election shall be conducted, returns made and notices thereof given as provided by the general election law. The question shall be in substantially the following form: ------------------------------------------------------------------------ Shall the county highway tax rate YES of.......... County be increased -------------------------------- to.....%? NO ------------------------------------------------------------------------