In the area of the northern entrance at the Liestal railway station, two double-track lines unite to form one. This causes the tracks of the trains to overlap, resulting in so-called intersection conflicts. The resulting narrow pass is a bottleneck in the long-distance traffic of the Swiss Federal Railways (SBB AG) and prevents an expansion of the train service in the Basel-Olten area.

With the projects "Four-track extension ZEB" and "Turning track STEP" SBB AG intends to resolve the intersection conflict and at the same time to expand the platform and track systems sustainably. This will ensure more punctual and trouble-free rail traffic on the Basel-Olten line. In addition, the expansion is one of the basic prerequisites for an expanded range of trains in northwestern Switzerland in the future.

Drees & Sommer was appointed as project manager in support of the main coordination team.