My understanding is that no-parking zones at intersections are designed to provide clear sight lines for drivers and pedestrians.
I just witnessed a common occurrence in our neighborhood: a USPS vehicle pulls up in front of the house across the street, parking in a no-parking zone. There is not a soul parked on that side of the street and by backing up one vehicle length the vehicle would have been parked legally. The vehicle then proceeded across the intersection and parked in another no-parking zone. By pulling forward one vehicle length, the vehicle would have been legally parked.
It seems to me that the safety issue is not dependent upon whose vehicle is doing the parking. USPS vehicles block sight lines as surely as any other.
I realize the village probably can’t ticket Postal Service vehicles, but I don’t think that gives the Postal Service the moral right to ignore safety laws. I could understand it if there were no parking spots available, but in this case, ample legal parking was available one vehicle length away. We have lots of foot traffic here, being one block from the high school, and more than our share of drivers who barely slow down for the four-way stop, so sight lines are an issue.
I would add that village vehicles sometimes do the same thing at our intersection, but the USPS is the primary scofflaw.