Since you didn't specify which "GDS" or which specific "Transport" typeface you are referring to, I have broken this down into the two most likely scenarios.
is a custom digital version of the iconic British road sign typeface, specifically optimized for the UK Government Digital Service (GOV.UK) . While highly sought after for its clarity, the official font files are strictly regulated and not available for general public download for external projects. 1. Origins and Design gds transport typeface download