 As I-10 heads south into downtown, it splits into an upper level with three lanes in each direction and a lower level with two lanes in each direction.It was necessary to design the freeway this way in order to accommodate the amount of traffic heading into downtown and to fit into the narrow corridor that was surrounded by existing infrastructure.I-10 meets I-35 on the northwest side of downtown and it overlaps I-35 south to form the west side of the downtown loop.