The commissioner of highways is empowered to enter into contracts for training programs with state colleges, universities and other training sources and to award scholarships to competent persons, whether presently employed by the division of highways or not, for the purpose of enabling and encouraging such persons to attend a college or university to pursue the course of study as may be approved by the commissioner of highways, but the number of persons holding such scholarships at any one time shall not exceed fifteen. Each scholarship shall carry a stipend in an amount fixed by the commissioner of highways not in excess of twelve thousand dollars in the aggregate. The necessary expenditures for the scholarships shall be made from the funds available to the division of highways. The recipient of a scholarship shall execute notes and shall deliver said notes to the commissioner of highways. Each note shall be in the amount of the sum received from the state road fund and shall be payable on demand to the division of highways. The commissioner of highways shall hold said notes and if, for any reason, except death or physical or mental disability, or being drafted into the armed services, the recipient of a scholarship fails successfully to complete the course of study for which the scholarship was granted or if after the completion of the prescribed course of study does not continue or become an employee of the division of highways, or ceases to be an employee before all the notes have been paid or canceled, the commissioner of highways shall make demand for payment of all of the unpaid and uncanceled notes and shall promptly enforce collection thereon and shall deposit the sums so collected thereon in the state road fund. The commissioner of highways is authorized to credit the oldest outstanding notes in the sum of one thousand five hundred dollars every six months that the recipient of the scholarship is employed by the division of highways after completing the course of study for which the scholarship was granted. The commissioner of highways shall have the power and authority to make all necessary rules to carry this section into effect.