Section 6. Cities and towns may, by a majority vote, incur debt for temporary loans for the payment of land damages or any proportion of the general expenses of altering a grade crossing which they are required primarily to pay, or any proportion of the expense of constructing a highway or installing traffic control devices and other devices appurtenant thereto, in anticipation of payment or reimbursement by the commonwealth or county, such payment or reimbursement first having been agreed upon by the commissioner of highways or county commissioners, or the sums allotted for such payments or reimbursements having first been certified as available by the commissioner of highways or county commissioners, and may issue notes therefor for a period not exceeding 2 years from their date; and when any money so paid is repaid to the municipality, it shall be applied to the discharge of the loan. Notes issued under this section shall not be renewed or paid by the issue of new notes, except as provided in section 17.