In my post on the bikes of Guangzhou I pointed out that many bikes had a double top bar. This is sometimes referred to as a "Pig Bar" because, allegedly it was designed to allow a pig to be carried to market.
I doubt this for several reasons.
1. In China, any weight carried on a bike is almost ALWAYS carried over the rear wheel, whether that be a passenger or a mountain of walnuts. Weight is NOT carried between the rider and the handlebar. This can be seen in the picture above.
2. If you were to put a pig or any other sizable cargo between the rider and handlebar the rider's knees would have no place to go. Pedaling would be impossible.
3. The double bar is probably not even a Chinese innovation. Take a look at the attached picture of this 1940's Hercules which I took in a Beijing Pawn Shop. Rudge made a similar bike and probably other European makes did as well. I'm guessing...and it is just a guess, that '40s British pig farmers probably preferred a lorry to a bicycle as a method of swine transport.
So why would you design a double bar? Because it strengthens the frame. Period. You can carry heavy loads, or just put it to heavy use and abuse on poor roads without worrying that the lugs will be shaken to bits. This is why this design is such a favorite among the delivery bikes of Guangzhou. It is strong and lasting. But a specific use such as "designed for carrying pigs to market" seems to be just mythology to me.
I would be interested in what other old bike aficionados have to say. Maybe someone knows better.
BTW: The double-bar Hercules is still made in India, albeit with side-pull brake rods, not center-pull.