In a collaborative project, Pipeline Research Limited and the Hydrogen Working Group of the Pipeline Operators Forum investigated In-Line Inspection (ILI) tool velocities for exemplary 6-inch and 30-inch hydrogen transmission pipelines under various conditions. The investigation focused on studying tool dynamics in a hydrogen environment by modelling ILI parameters, operating conditions and pipeline design. Options to control tool speed excursions are investigated to limit the velocity to less than maximum allowable. This maximum is taken as a typical threshold from a safety perspective but also for effective inspection and data collection. The requirements for the tool, control of pressure, inlet and outlet flow and special arrangements such as bypass are studied for both pipelines to allow successful and safe inspection. This investigation sets out opportunities and functional requirements for improving tool velocity control in hydrogen pipelines. Meeting these requirements may pose a challenge to operators and inspection companies in terms of practicality and limitations of current technology.