Notwithstanding the provisions of any law to the contrary, the county board of Hennepin County may appropriate from its road and bridge fund to any town or city within the county, such sums of money as are available and which the county board deems advisable to aid any such town or city in the construction and maintenance of roads, streets or bridges therein. The appropriations may be directly expended by the county board on roads, streets or bridges designated by the governing body of the town or city, and may be expended in accordance with Laws 1905, chapter 164, as amended. No such town or city shall receive an appropriation hereunder exceeding 30 percent of the annual county tax levy for road and bridge purposes paid by the town or city.