3 ideas
A four-level stacked interchange separates each turning movement onto its own dedicated ramp at a distinct vertical level, eliminating the weaving and signal stops that plague at-grade crossings. By assigning every directional flow its own plane, traffic from intersecting highways never crosses paths at the same elevation.
A symmetrical interchange design implies that each connecting highway is treated as carrying comparable directional demand, with matched ramp geometry on all sides. This balance trades land footprint and construction cost against the ability to handle high volumes equally in every direction.
Reading an interchange by its number of levels reveals a core spatial choice: stacking ramps vertically conserves horizontal land but increases structural height, expense, and visual prominence. The 'four-level' descriptor itself becomes a shorthand for how a junction resolved the tension between space, money, and throughput.