Answering the public's questions about the US mail

Most users of the US Postal Service complain - or wonder - about many of the same things. Here are some of those questions, and paraphrased responses by the National Academy of Public Administration panel that has just evaluated the service:

Why do patrons often have to wait in long lines and sometimes meet with discourtesy?

Long queues and discourtesy are more prevalent in big than in small post offices. Unions say there are too few clerks, who are often harried by patrons. In an attempt to shorten lines, the service is making available more self-service facilities for stamps, etc. Recent emphasis has been on productivity, not client relations. The panel recommends efforts to address public complaints.

Will postal rates continue to rise?

It is clear that postal rates will go up, except where employee productivity makes for savings. Also, reduced US subsidy for certain bulk mailing by nonprofit organizations will mean increases in that category.

Will the proposal to discontinue Saturday mail delivery come up again?

It could. The Postal Service still has doubts about stopping it. One concern is over the possible backup of residential mail over the weekend. But the panel says research shows public reaction would not be unfavorable, and it points out that $400 million to $500 million annually could be saved.

Why not end the Postal Service's ''letter monopoly''?

Immediate savings to big mailers in metropolitan areas are insufficient compensation for the disruptions that would follow. Uniform national letter rates would end. The system would be ''Balkanized,'' since remote areas and those with low population density would be economically severed from major metropolitan areas. The private cost or public subsidy necessary to connect the two inevitably would rise.

What is the error rate in mail-sorting?

Using sorting machines that require workers to read an address and make a sorting decision within one second, the error rate is 5 percent; that is reduced to 2 percent by a backup system called ''riffling.'' No one is suggesting a return to hand-sorting.

What about the nine-digit ZIP code?

If the Postal Service had done a better job of informing the public on how much the longer ZIP would improve delivery, it might be in use now.

If you were grading on a scale of A-F, what mark would you give the Postal Service?

B-plus, especially in comparison with the old US Post Office system.