The ranking in this dataset is concentrated among a small group of large rolling-stock manufacturers, most of them Chinese state-affiliated groups such as the China Railway Rolling Stock Corporation family of subsidiaries. Several of these same assignees show zero filings in the most recent tracked year, so current leadership on paper does not necessarily mean current filing activity. A practitioner should check both the cumulative count and the recent-year momentum before assuming a given company is still actively expanding its position.

Filings in this corpus rose from 16 in 2017 to a peak of 30 in 2021, then fell to 21 by 2022 and kept declining through the most recent partial year. Part of that late decline is a publication-lag artefact — patent applications typically take around 18 months to publish, so the last one to two years always understate true filing activity. But the drop-off starting well before the most recent years, at the 2022 midpoint, suggests a genuine cooling in new filing rather than just an artefact of lag.

China is by far the largest receiving office in this dataset, with 129 of the 249 tracked families, more than three times the next office. The European Patent Office follows at 36, the United States at 18, and Russia, Australia and India make up smaller shares. This distribution means most enforcement risk and most freedom-to-operate diligence for this claim space needs to start with Chinese filings rather than European or US equivalents.

Nearly all records sit in B61F, the core railway running-gear and bogie classification, but durability-specific claims increasingly extend into B61C (locomotives and railcars) and B61B (railway systems and cableways). Smaller but present clusters in B60L propulsion, B61H brakes and G01M testing show durability claims occasionally crossing into adjacent subsystems and test methodology rather than staying confined to the bogie frame alone. This spread is worth watching because it suggests durability claiming is becoming a vehicle-level concern, not just a component-level one.

Not clearly, based on the tracked trend: after peaking at 30 families in 2021, filings fell to 21 by 2022 and continued declining into single digits by the most recent partial year. Some of that apparent decline reflects publication lag rather than an actual stop in filing, since recent applications simply haven't published yet. The more reliable read is the multi-year decline through the 2022 midpoint, which points to a genuine slowdown in new filing rather than a technology in an early growth phase.