Danny Hakim:

With a faint electric whir, Iris Marossek pedals her bicycle through concrete apartment blocks in the heart of old East Berlin, delivering mail to 1,500 people a day.
 
 Painted yellow and black like a bumble bee, her bicycle is a nod to both past and future. It is decorated with an image of a curving black horn, harking back to earlier centuries when German postal workers trumpeted their arrival. But the twin battery packs under her seat also reveal it is more than the average bike.
 
 Ms. Marossek rides one of the 6,200 e-bikes in service for Deutsche Post, the German mail service. E-bikes use electric motors to make them easier to pedal and have been gaining popularity in bike-loving countries like Germany, appealing to older people, delivery businesses and commuters who don’t want to sweat.