SECTION 11. State aid for keeping highway open in winter

The department of highways may co-operate with the proper officers of cities, towns and counties in keeping open and reasonably passable for vehicles during the winter months such highways as may be selected by said department, having regard to the importance thereof for commercial uses and the co-operation and aid to be rendered by cities, towns and counties and persons in carrying on this work, and for this purpose may expend such sums as may be annually appropriated therefor and may accept financial or other assistance from any city, town, county or person; provided, however, that the work carried on under this section shall be supplemental to work undertaken and performed by cities and towns under other provisions of law, and that nothing in this section shall render the commonwealth liable for damages for which it is not liable under other provisions of law or relieve cities or towns from keeping their highways clear from ice and snow as required by other provisions of law.