Answer
In the Netherlands, helmet use is not mandatory for pedelecs (pedal assistance up to 25 km/hour), since pedelecs are classified as ‘ordinary’ bicycles. Speed-pedelec riders do have to wear helmets (special speed pedelec helmets or moped helmets; not ordinary bicycle helmets), because a speed pedelec is legally a moped. For more information see SWOV fact sheet Pedelecs and speed pedelecs.