Surveillance in Public Transit: How Bremen Implemented Behavior Scanners

• The Bremen Transport Authority (BSAG) installed behavior-scanning software in its trams after a failed attempt to procure a system for detecting vandalism, eventually opting for 'aggression detection' software from the firm 'Just Add AI'.
• Despite questionable results during the testing phase, the technology was deployed in 43 trams, accounting for one-third of the fleet.
• Data protection authorities have sharply criticized the project for its lack of efficacy and failure to adequately address passenger privacy rights.

Origins and Implementation

• BSAG originally sought an automated system to document vehicle damage, but the vendor claimed this was technically unfeasible and proposed an aggression recognition system instead.
• The pilot project, launched in March 2025, revealed significant operational flaws: during the first five months of testing, the system generated 16 alerts, only four of which corresponded to actual recorded incidents.
• There is currently no clear protocol for how tram drivers or dispatchers should respond to these automated alerts.

Privacy and Ethical Concerns

• The vendor uses pixelation to mask faces, but data protection officials warn that this is not true anonymization, as individuals can still be identified by tattoos or clothing, and pixelation can potentially be reversed.
• The system risks disproportionately targeting vulnerable groups, such as homeless individuals, by misclassifying 'sleeping' as a 'dangerous situation' or 'aggression.'
• The project is partly funded by federal digitization subsidies, despite the lack of evidence that such scanners increase transit security.

Broader Implications and Outlook

• Bremen's move is part of a nationwide trend, with similar AI monitoring projects planned or underway in Mannheim, Hamburg, Berlin, and other states.
• Data protection authorities have mandated a comprehensive evaluation after one year of operation to determine if the system's rate of false positives makes it disproportionate and subject to termination.
• In Mannheim, where similar technology has been tested for eight years, authorities have yet to identify a single instance where the system contributed to preventing or solving a crime.