I work for the government. There are rules that dictate everything. I'm having a hard time believing that there isn't something written that dictates everything the USPS does.
That said, the interaction between my neighbor and the carrier (coincidentally the post master) was about speed. After a pissing contest, the neighbor said don't come down here anymore. Post Master said ok. Which is bullshit. I understand cutting off part of a route due to a safety reason. This is far from that.
You say they don't have to come down private roads, but every time I search that it says,
- For Accountable mail items and oversized parcels (not postage due), the carrier must try to gain the attention of the recipient, which includes honking their horn, in order to get them to come to the vehicle. If the customer doesn't come out and the house/delivery point is within 1/2 mile of the line of travel AND has a passable road, the carrier should attempt to deliver it. Otherwise, the carrier will leave PS Form 3849 and the customer will have to make arrangements to obtain the item.
There also seems to be different rules for every area stemming from when that area was established and what services were requested at that time.
