As part of the Stuttgart 21 infrastructure project, the Stuttgart rail hub is undergoing a complete overhaul. The goals are to reduce travel times for regional and long-distance rail service and to connect the airport to the long-distance rail network. The existing Stuttgart Central Station is being converted into an underground through station. Adjacent rail lines are being rerouted, and the necessary civil engineering structures are being constructed to address topographical challenges.

Already during the planning phase and throughout construction, relevant specifications were implemented and verified to assess compliance with the touch voltage limits required by EN 50122-1. The goal is to confirm compliance with EN 50122-1, TSI ENE, and DB Ril. 997.02, or, if necessary, to implement remedial measures in advance.

In May 2025, so-called high-voltage test runs took place on the section of track from Merklingen to the airport connection. These test runs are used to determine the contact voltages that occur. During these runs, the traction current and the track-to-ground and contact voltages are measured at representative locations along the route using the DB ICE-S test train. The results of the network calculations allow the contact voltages to be calculated for both normal operation and fault conditions. Further high-voltage test runs are in preparation.