Frankfurt's Digital Train Control project is a pioneering smart mobility initiative that introduces Communications-Based Train Control (CBTC) and Cooperative Intelligent Transport Systems (C-ITS) to the city's underground and surface rail network. The project, which began its first test runs in 2025, represents a first-of-its-kind combination of underground rail automation and street-level traffic coordination in Germany.
The CBTC system enables semi-automated subway operations by replacing traditional fixed-block signalling with continuous digital communication between trains and trackside infrastructure. This allows trains to operate with significantly shorter headways — the time between successive services — enabling more passengers to be transported on existing infrastructure without the need to build new tracks or tunnels. The system also improves energy efficiency through optimised acceleration, braking, and coasting profiles calculated in real time.
A distinctive feature of Frankfurt's project is the integration of CBTC with C-ITS technology at surface level, where underground trains emerge onto street-running sections. Traffic signals automatically detect approaching trains and adjust their phases to provide priority, reducing delays at intersections and improving journey time reliability. This intermodal intelligence ensures that the benefits of digital train control extend beyond the underground sections into the broader urban transport network.
The project is being rolled out progressively, with all relevant lines expected to switch to the new system by 2033. Frankfurt's experience serves as a significant reference case for other European cities seeking to increase the capacity and efficiency of their rail networks through digital technology. The integration of underground and surface transport intelligence in a single system represents an important advance in smart urban mobility.