A friend of mine from way back was a postman who rode the motorbike. The really interesting part about this was a recurring complaint among posties about back injuries, because they would pull up at the postbox right on the footpath, stay seated on the bike, and twist to put the mail in the slot.

Of course, the bicycle riders would stand and the twisting motion wasn't so aggravated. So there are some interesting physiological issues that start to emerge when "efficiency" is mechanised. In the end, with time off work, one wonders how efficient that efficiency really is.

I should also say that the bicycle postal people I've seen have been contractors in small towns, not the cities.