The street crossings of the Union Pacific Railroad Company right-of-way at Avenues “B”, “E” and 16 in the city be and the same hereby are closed to vehicular traffic; provided, however, that, said street crossings shall be kept open for the use of pedestrians and that suitable crosswalks be maintained for public use at said avenues; and, provided further that, nothing contained in this article shall be construed as an abandonment or vacation of the easement or grant of passage for public use at the crossings of the Union Pacific Railroad at Avenues “B”, “E” and 16.