feet at the top (0.6 meter, more or less), the shorter columns were likely to break, since the rigid deck structures cause the imposition of a similar amount of motion at the tops of the columns, imposing more bending stress per unit length on the shorter columns. This problem was solved by making the columns of similar (but not uniform) length, with the "shorter" columns extending in permanent open shafts to deep foundations. This allows all columns of the YBITS to respond in a sufficiently uniform manner. The space between a column and its pit is covered by a protective sacrificial cover, forming a type of base isolation system at the more sensitive column locations. In addition, the western landing of the YBITS is a zero moment hinge, and so there are no vertical bending stresses at that point. Construction techniques The construction process to build this structure consists of several steps, shown below: The first step is to construct foundations of the large columns that will support the elevated roadway of the YBITS. Above-grade column reinforcing is constructed and enclosed by formwork and concrete is poured. After curing, the formwork is then removed. The next step is to build the roadway itself. The spans were cast in place, using extensive reinforcing, with post-tensioned cable tendons. The roadways consist of hollow box structures, cast in place in sections using formwork, owing both to the complex shapes involved and the necessity of maintaining traffic flow on adjacent structures during construction. The following sequence is applied to each span between columns: Since the wooden or metal form that supported the casting of the concrete was elevated, the forms were supported on falsework, in this case using vertical pipe sections, steel beams, and diagonal cables. A wooden deck was then erected atop the falsework to support the lowest forming surface. Reinforcing for the lowest surface of the box structure was then added, and the concrete was poured. During the initial pour, reinforcing and formwork for interior shear beams and any included tendon conduits were added. Later, another concrete pour was performed. Then interior formwork to support the upper (deck) surface was added and the rebar-pour process was repeated. After the concrete is sufficiently cured and any tendons were tensioned, the formwork and falsework was removed, leaving only the concrete surfaces. Island ramps Other than the current westbound off ramp, existing ramps linking the