Explanatory document on proposed amendments to UN R168 to enable real driving emissions testing of hydrogen internal combustion engine vehicles. The work-based approach replaces the CO-based moving averaging window methodology currently inapplicable to hydrogen-fuelled vehicles. Engine speed and torque data replace carbon monoxide to define window size and calculate the RDE/WLTP work ratio. Testing of a light commercial vehicle demonstrates the methodology’s practical applicability under regular and severe driving conditions, with results processed through independent post-processing tools.