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The journey of a letter or package begins with dropping it into a mailbox or handing it over at a local post office. What happens next involves a network of facilities, sophisticated machinery, and dedicated personnel working to ensure your mail reaches its destination.
Every day, the USPS handles more than 173 million pieces of mail. Here’s how it happens.
Mail Collection
The process starts with collecting mail from various sources. Postal carriers gather outgoing letters and packages from individual mailboxes, businesses, and collection points throughout their routes. This collected mail is transported in bulk to a central mail processing plant, typically by truck.
Consolidating mail at a central location allows for efficient processing and distribution, rather than individually routing each piece from its origin.
Types of Sorting Facilities
The USPS operates several specialized sorting facilities, each with distinct roles:
Processing and Distribution Centers (P&DCs)
These major regional hubs handle the initial processing and dispatch of mail within specific geographic areas. Mail arriving from local post offices and collection boxes within the region first goes to a P&DC.
These centers receive, sort, and dispatch mail to local post offices for final delivery or to other processing facilities for further sorting. P&DCs function as regional clearinghouses, managing the initial flow and direction of mail.
Local Processing Centers (LPCs)
LPCs focus on more localized sorting, handling letters and flats destined for individual mail carrier routes within a regional area. They also manage some package sortation.
These centers prepare mail for the final leg of its journey, organizing it according to specific carrier routes for delivery to individual addresses.
Network Distribution Centers (NDCs)
Also sometimes called regional facilities or service hubs, NDCs handle larger volumes of mail and packages traveling across greater distances. These facilities consolidate the processing and distribution of bulk mail and packages across broader regions.
Within these centers, mail from initial traveling pallets is broken down and reorganized onto new pallets based on destination. Service Hubs operate similarly to NDCs, acting as down-flow mail facilities for efficiently moving mail toward delivery units.
Sorting and Delivery Centers (S&DCs)
A newer type of facility in the USPS network, S&DCs represent a modernization effort. They aggregate mail carrier operations from several smaller existing locations into larger, more efficient facilities.
S&DCs aim to enhance efficiency, provide infrastructure for electric delivery vehicles, and improve the speed and accuracy of package sortation.
Automation Technology
The massive volume of mail processed by the USPS requires significant automation. Machines play a crucial role in reading, sorting, and speeding up mail delivery.
Automated sorting machines initially separate mail by shape and size – a process called culling. These machines also orient mail pieces so addresses face the correct way for subsequent processing.
Different specialized machines handle various types of mail:
- Delivery Bar Code Sorters (DBCS) for letters
- Flat Sequencing Systems (FSS) for larger, flat mail like magazines
- Small Package Sorting System (SPSS) and Enhanced Package Processing System (EPPS) for packages
- High Output Package Sorter (HOPS) and Automated Flat Sorting Machine (AFSM)
These machines can sort thousands of pieces of mail per hour, essential for managing the vast quantities efficiently.
Barcode Technology
Barcode readers within sorting machines scan unique barcodes printed on each mail piece. These barcodes serve as digital identifiers, encoding destination information necessary for automated routing. By reading these codes, machines direct mail to appropriate bins, guiding it through the network toward its final delivery point.
Optical Character Recognition (OCR)
OCR systems interpret addresses printed or handwritten on mail pieces. When OCR successfully reads an address, it generates a corresponding barcode used for automated sorting.
If OCR cannot decipher the address, the mail piece may be flagged for manual processing or sent to a remote encoding center. There, human operators view images of the mail and manually input address information to generate a barcode.
OCR bridges the gap between human-readable addresses and machine-readable barcodes, expanding the scope of automated sorting.
| Technology Name | Function | Examples |
|---|---|---|
| Automated Sorting Machines | Separates and orients mail, sorts by destination | DBCS, FSS, SPSS, EPPS, HOPS, AFSM |
| Barcode Readers | Scans barcodes for automated routing | Handheld scanners, integrated readers |
| OCR Systems | Reads and interprets addresses to generate barcodes | MLOCR |
The Sorting Process
A mail piece goes through several key stages at a sorting center:
- Receiving: Mail arrives at the processing center from local post offices and collection points.
- Separation by Shape and Size: Machines categorize mail into letters, flats (large envelopes, magazines), and packages. Each type requires different processing equipment and handling.
- Facing-Canceling: Letters are oriented so addresses are uniformly positioned and right-side up. Simultaneously, postage stamps are canceled with a postmark to prevent reuse. Proper facing allows OCR and barcode reading systems to function effectively.
- Barcode Application: A unique barcode representing the destination address is applied to each mail piece, either sprayed directly onto the envelope or printed on a label. This barcode drives subsequent automated sorting.
- Sorting by Destination: Automated sorting machines read barcodes and direct mail pieces into designated bins based on ZIP codes. This process often occurs in multiple passes, starting with broader regional ZIP codes and becoming increasingly specific, ultimately sorting mail down to individual carrier routes.
- Dispatching: Sorted mail is bundled, placed in trays, or loaded into containers for transportation to the next processing facility or the final destination post office.
The Human Element
While automation is critical, the people working in these facilities are equally essential. Human employees provide crucial oversight, problem-solving, and maintenance that automated systems cannot handle independently.
Key roles include:
- Mail sorters, processors, and machine operators who examine, sort, and route mail, as well as operate sorting machinery
- Supervisory personnel who oversee operations, ensuring efficiency and accuracy
- Mechanics responsible for equipment maintenance
- Drivers who transport mail within the facility
These roles require specific skills: a sharp memory for recognizing sorting codes, good hand-eye coordination, the ability to read quickly and accurately, and physical stamina for standing and lifting tasks.
Package and Flat Processing
Packages and flats undergo slightly different sorting processes compared to standard letters due to their physical characteristics.
Packages, with diverse sizes, weights, and shapes, require specialized handling. While automated systems like SPSS and EPPS process many packages, larger or irregularly shaped items may need manual sorting by USPS employees. Throughout their journey, barcode tracking provides visibility into the location and status of packages.
Flats, including magazines and large envelopes, have dedicated sorting machines such as the AFSM and FSS. Sorting flats presents unique challenges due to variable sizes and inconsistent address placement.
Security Measures
The USPS prioritizes security within its sorting centers to protect mail from theft, damage, or tampering. Security measures include:
- Surveillance systems monitoring activities within facilities
- Access control systems restricting entry to authorized personnel
- Package tracking technologies monitoring mail throughout processing and delivery
- Employee training to report unfamiliar individuals or unbadged visitors
- Secured postal vehicles and facilities to prevent unauthorized access
The USPS has initiatives like Project Safe Delivery to enhance security efforts. USPS facilities are federally protected properties, providing a legal framework for mail security.
Future Modernization
The USPS continuously works to modernize its network for greater efficiency and cost savings. Key aspects include establishing new types of facilities:
- Regional Processing and Distribution Centers (RPDCs)
- Local Processing Centers (LPCs)
- Sorting and Delivery Centers (S&DCs)
These changes aim to streamline operations, leverage technological advancements, and adapt to evolving mail and package delivery needs.
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