Switzerland's Federal Office of Transport (BAV) tightened safety requirements for freight wagons following a 2023 derailment in the Gotthard Base Tunnel (the world's longest railway tunnel, running beneath the Alps) caused by a broken wheel on a German DB freight train, which left the tunnel partially out of service for nearly a year and caused roughly 150 million francs in damage. The new rules, which apply to all freight wagons passing through Switzerland including those from EU member states, mandate more frequent maintenance, improved inspections, and stricter minimum wheel-diameter standards. The European Union has criticised the move as a unilateral measure that risks disrupting Alpine transit flows and fragmenting the EU single market, with compliance costs estimated by Brussels at between 150 million and one billion euros annually — though Switzerland contests those figures as greatly exaggerated and insists the measures are legally permissible under the bilateral land transport agreement. EU transport officials plan to raise the dispute at a joint supervisory committee in June, and expect Switzerland to withdraw its national rules once a harmonised European standard — currently being developed by a European Union Agency for Railways task force to which Switzerland belongs — is in place; the dispute is unfolding as Switzerland's parliament debates a broader new bilateral package with the EU that includes updated dispute-settlement mechanisms.