How does the distribution network of the post office work

If you mail something from a small town in california to a small town in New York its obvious they don’t take the letter directly. I assume there is some kind of hub and spoke system. So how does it work?

Are there certain tiers of post office (1, 2, 3, 4, etc) and if you mail something from a lower tier, they move it to the nearest high tier office which transports it across the nation. For example, if your small local california town is a tier 4 post office, they movie it to the nearest big city (maybe los angeles) which is tier one, then they ship it to the nearest tier 1 office near your destination (maybe NYC).

I’m guessing I don’t know. How does it work? Sometimes when tracking my mail it makes stops in large cities that aren’t close to my large city, so I don’t know how it works.

I assume there are a variety of options the PO can use including some combination of Planes, Trains (rarely), and Trucks, and they have software that figures out the best routing time-wise based on schedules and distances. I live in a very small town, but 30 miles up the road is a bigger town with an airport with flights out to major hubs every day. the PO may have a contract with United Airlines for my state and that means it gets routed to Denver. From there it finds a way to get to an airport close to the destination or to someplace with trucks that are scheduled to go to my destination. They have 2-3 days to get it there so they have a number of different options depending on weather and other factors. I am sometimes amazed at how quickly a letter from far away can get to me, and sometimes how long it takes for it to reach me. I give the PO a week to deliver 1st class mail or packages and they usually beat that by at least 3-4 days.

Typically, a network of trucks takes the mail to the sectional center facility (SCF) serving your ZIP code; there are sixteen in California. These are not post offices themselves, in that most of them don’t have a retail window at all. Instead, they are purely sorting and processing plants. (In some areas, a dedicated unit within a larger post office does some processing and distribution for the immediate vicinity.)

Mail destined for other locations within the SCF service area will be routed to the appropriate post office; otherwise, it is shipped on to the Network Distribution Center or NDC, of which there are 21 in the US, for transport to the NDC and thence to the sectional in the destination area. From small-town California, the mail goes to the local sectional, then most likely to the Los Angeles NDC, then straight through to the New Jersey NDC, then to whichever one of the dozen or so SCFs serves the destination ZIP code in New York, thence to the local post office. It is very much a hub-and-spoke system, and the USPS has been consolidating their processing centers for a number of years now.

But you may be interested to know how it worked in an older, gentler era:

Mail would be sorted into bags at your local post office. Perhaps one bag for local mail, one bag for each of the nearby post offices, one bag for the city, and one bag for out-of-area mail. Then the local mail would be sorted to delivery routes, the nearby bags and city bag would be sent to their post offices, and the out-of-area mail – interstate, overseas, whatever – sent to a regional sorting center. Postmen would get their delivery bag, and before leaving the post office would sort the mail to delivery order.

I lived in a large state institution. Our mail address was a mail bag (“Bag 1”), and when sorting to delivery routes, our local post office would sort our mail to that bag.

Nowadays, they use zip codes instead. If the institution is big enough, it has its own zip code. GE in Schenectady is 12345, for instance.

Shipping/mailing logistics can do seemingly illogical things when you have multiple tiers of service too. Ground or 1st class can take a different route than 2nd day air which can take a different route than overnight for example. There’s an online store I occasionally order from, and their distribution center is actually just 20 minutes away in one of Cincinnati’s northern suburbs. However if I order something using their free shipping, it goes to a distribution center in Columbus before coming back to Cincinnati. I assume this is because they’re filling a truck or a regularly scheduled pickup on a pre-planned route direct to that regional distribution center that then routes to the local distribution center(s).

That’s also why companies like UPS and FedEx have different vehicles and drivers for different service levels. The ground driver does a relatively “normal” route with additional dropoffs and pickups as needed, whereas the express driver probably doesn’t have a normal route and all their pickups and deliveries are “special.” I think the USPS does this too, but their vehicles are not as obviously marked/branded as such.

The UK is, of course, a much smaller geographical area but the GPO works in a similar way. Postcode (like ZIP codes) were introduced back in the 60s and divide the country into areas, districts and local units (which may be a few houses or a single large customer).

Every district has a Sorting Office which is where the postpeople are based. There is a letterbox within half a mile of 98.3% of all addresses in the UK where letters and small packages can be posted. Some are also found in supermarkets and shopping centres.

Postpeople sort the mail for their “walk” and set off to deliver it once every day (twice in city centres). In this country, they have to push it through a slot in our front door or sometimes a slot on a box at the gate. At one time collecting the mail in the letterboxes was a separate job, but these days, the local postperson will empty them at the same time as they do their rounds. They also have secure storage boxes where they can leave part of their load for later.

All collected mail goes to the local sorting office where it is either roughly sorted into areas, or simply loaded into vans to be taken to a “Main” sorting office. A Main sorting office has high-speed sorting machines which read the postcodes and direct the mail to bags for onward transmission to either another Main office or a local office, where the whole process is repeated.

I live in a small town in the Midlands, so a letter I put in the box on my road will be collected and taken to our local sorting office. They send all their mail, even the mail for the same town, to Birmingham, where it gets sorted and sent on, or back as required. Overseas mail goes to another sorting office in London. If I post a letter in my local box this afternoon, it will not be collected until tomorrow morning, but I could walk to the local post office which has several collections daily (last one at 5:30 pm). My letter should be delivered the day after posting anywhere in the country if I pay for a 1st class stamp, otherwise, it can take up to three days.

FedEx does that because they acquired the ground company and never integrated their systems together.

From the perspective of a shipper, FedEx express vs ground act as if they are almost two different companies, separate trucks to pickup, separate manifests on the back end, separate scheduling (e.g. saturday pickups during holiday), etc.

UPS picks up express and ground on the same trucks (for us at least).

I’ve seen both. Sometimes it’s the same guy/truck but a different run. The express deliveries/pickups more often tend to be with their smaller sprinter vans (on which their brown livery is not at all flattering).

FedEx also has more than Express and Ground, they also have Home, Freight, Trade, Custom Critical, and a few other more logistics-y ones. I see Express, Ground, and Home delivery trucks regularly.

I remember ~20 years ago or so. The post office had two blue collection boxes, one for local mail and one for out of town mail. But that wasn’t a really long time ago, just a decade or two. Maybe computers advanced enough that they didn’t need to sort the local vs non local mail like that anymore.

Does it always go as high as the SCF though? Let’s say I decided to mail something to the local junior college- it’s like a half-mile away within my zip code. Wouldn’t a letter to them just go to the local post office and get delivered without actually going as high as the SCF?

I always thought the USPS had a sort of scheme where if it can be delivered within (or below) the current level it is, and if it’s not within that area, it gets punted up a level to be sent around. So if the letter isn’t at the local post office, but is within the zip codes served by the SCF, it gets punted up to the SCF, who routes it down to a local post office within its area if if it’s in the proper zip codes. If it’s not to a zip code served by that SCF, it gets punted up to the NDC, where it may be routed within the area served by the NDC, or if not within that area, routed to the appropriate NDC.

That’s what I was alluding to earlier. It might do that, but if it’s low priority it could just as easily get chucked into a bin to go to the regional sorting facility and eventually work its way back. The local PO may not have the capacity to process or hold every mail item that comes in, so it’s limited only to higher priority items. Those huge centralized processing facilities are so fast and streamlined with their state-of-the-art scanners, conveyors, sorters, and teams of people to read hand-written addresses and interpret missing information or ripped barcodes that it’s just more efficient and usually still faster to ship as much mail there as possible. Granted the actual tiers of service are different in the USPS as compared to UPS or FedEx, but the logistical implications are similar enough.

All First Class mail has to be routed through the P&DC that serves the carrier facility. Note that although they are often in the same building, a carrier facility is not necessarily in the same place as your local Post Office, so even if you go to a retail facility to drop off a letter, that is not necessarily the same building from which your carrier works.

In the olden days, mail would arrive at the carrier facility in trays sorted by carrier route and carriers would sit at sorting cases in the morning before going out on their routes and sort the mail in delivery order, tray it, and take it out. This is no more. The mail arrives from the P&DC trayed and sorted in walking order and the carrier picks up the sorted trays, loads their vehicle, and goes out to deliver.

If you wanted to bypass the P&DC you would have to have people at the local Post Office who would take your mail and somehow merge it into the trays of mail from the P&DC in proper walking sequence. The expense of this is just not worthwhile.

Parcels, however, are different. Overnight, your local carrier facility has UPS, FedEx, Amazon, and other direct entry shippers pull in and drop off cages or pallets full of pre-sorted parcels. But even then, the parcels have to be pre-sorted to certain standards so that they will require minimal sorting at the carrier facility.

There was an annoyance over this issue in my old hometown a few years ago. The post office closed down the regional sorting office in Plattsburgh, NY and shifted all its mail handling to the regional office in Albany. This was reportedly done because the Albany office wanted to handle a larger amount of mail in order to avoid budget cuts.

But it was annoying to people in northern New York because if you were mailing a letter between two towns that are ten miles apart, it used to be processed through Plattsburgh within a day. Now that letter travels down and back to Albany, over a three hundred mile round trip and it gets sorted slower because of the larger volume of mail in Albany. It adds about a two day delay to a letter that’s only traveling ten miles.

Since it’s no longer sorted locally, there is no such thing as ‘local mail’ anymore. It all goes to the big sorting center.

And back when they did that, there was a difficulty in that humans were inaccurate – often they mixed up those two blue boxes and put out-of-town mail in the local-mail box, or vice versa. Not a big problem; when the guy sorting the local mail found an out-of-town letter, they just tossed it into the bag going to the bigger sorting center. But often today’s truck to that center had already left, so it stayed there until tomorrow’s truck. Thus adding one day’s delay to delivering that letter, which could lead to customer unhappiness. I was once told that 10-15% of the mail deposited in those 2 blue boxes would be put into the wrong one.

This may be kind of interesting.

A friend who used to drive for Royal Mail told me that trucks at sorting offices left at their scheduled times even if they were empty. He would drop a trailer on a loading dock and back under another one. At 1148 (or whatever) the bay doors would close and he would pull off. He had to close the trailer doors so he would see what kind of a load he had.

No ordinary haulier would work like this - they always want to maximise loads. Royal Mail’s priority is not transport but sorting the mail through the depots. That often depends on having a trailer ready to receive the sorted mail.