More modern ones do have front and rear caliper brakes. But the traditional oma/opafiets bikes use the pedal to activate the rear wheel hub for a brake. This is

More modern ones do have front and rear caliper brakes. But the traditional oma/opafiets bikes use the pedal to activate the rear wheel hub for a brake. This is fine for a casual Dutch ride. The only big downside is that you cannot backpedal a bit to raise the inside pedal when coasting and turning sharply… so you may hit your pedal on the ground and get an unpleasant bounce. But really, most new bikes have abandoned such old brakes.