Why This Bicycle Needs Two Chains [video]

Which also gives the explanation, for those like me who find it faster to read than watch a video:

> [It is] a stronger, simpler, and more sustainable bicycle that addresses the critical mobility needs of communities where transportation is a significant barrier to accessing essential services. ...

> This drivetrain consists of a switchable freewheel with two cogs, each paired with its own single-speed chainring and chain. Riders can easily switch between high gear for speed and low gear for climbing by back-pedaling half a turn, then pedaling forward.