On 1 January 2025 the Czech Republic began moving 622 km of main lines to exclusive operation under the European Train Control System, completing the change in four weekly steps. The track, the gauge and the axle loads stayed as they were. What changed was the rule deciding which trains could use those lines: under exclusive operation, a train not equipped with ETCS may not run on the section. In late November 2024 the Czech Rail Authority counted 1,442 fitted vehicles against about 1,500 needed for January, and said the required numbers would be reached. In April 2026 the Czech Supreme Audit Office concluded that the system had delivered higher safety and reliability but not the expected gains in capacity or speed, and that freight trains in particular had to slow down on some sections. The episode illustrates a constraint that kilometre counts of signalling deployment do not capture. A line that is physically fit for a train, and even fitted with ETCS, becomes usable capacity only when a vehicle with a compatible on-board configuration, demonstrated compatibility with the trackside, an authorisation covering the relevant area of use and a positive route compatibility check is actually available. For European military mobility, which relies on commercially contracted locomotives, the question is how much of the fleet can be converted, authorised and contracted in time for the routes defence would use.