Chapter 15: The Postal Codes - PostNET and PLANET |
Summary |
This chapter examines the postal barcode systems developed by the United States Postal Service (USPS) to automate mail sorting and tracking. PostNET (Postal Numeric Encoding Technique), introduced in the 1980s, encoded ZIP code information using a simple two-state system of tall and short bars, enabling automated sorting machines to process mail at speeds previously unimaginable. Its successor, PLANET (Postal Alpha Numeric Encoding Technique), employed the same two-state approach but was designed specifically for mail tracking and delivery confirmation services. Both systems were ultimately replaced by the Intelligent Mail Barcode (IMb), a more sophisticated four-state barcode that combined the functions of its predecessors while adding significantly greater data capacity. This evolution reflects the broader trajectory of barcode technology, where increasing demands for data density and functionality have driven the development of more complex symbologies. The story of postal barcodes is not merely a technical footnote but a case study in how automation, data encoding, and logistics intersect to shape the physical world of mail delivery. |
|
Introduction |
In the vast machinery of modern postal services, efficiency is measured in fractions of a second. Every letter, every flat, every parcel must be sorted, routed, and dispatched with mechanical precision to reach its destination. The United States Postal Service, handling billions of pieces of mail annually, faced a challenge that demanded a technological solution: how to make addresses machine-readable with speed and accuracy. |
The answer came in the form of postal barcodes. Before these specialized codes, mail sorting was a labor-intensive process requiring human eyes to read addresses and human hands to direct mail into the appropriate bins. The introduction of optical character recognition (OCR) helped, but OCR had limitations---handwritten addresses, unusual fonts, and poor print quality could confuse even the best systems. Barcodes offered a more reliable alternative: a machine-readable language that could be printed directly on mailpieces and read by high-speed scanners. |
The story of postal barcodes is a story of progressive refinement. From the relatively simple PostNET system to the more capable PLANET and finally to the sophisticated Intelligent Mail barcode, each generation brought greater functionality and efficiency. These systems did not emerge in a vacuum; they were shaped by the practical realities of the postal environment, where speed, reliability, and cost-effectiveness are paramount. |
This chapter traces the development and legacy of PostNET and PLANET. We examine their technical characteristics, their roles in the postal system, their industry applications, and their eventual replacement by the Intelligent Mail barcode. In doing so, we see how a seemingly humble barcode can transform an industry. |
|
The Genesis of Postal Automation |
The drive to automate mail sorting gained momentum in the postwar era. By the 1980s, the volume of mail handled by the USPS had more than tripled since World War II, and traditional manual sorting methods were no longer sustainable. The USPS had already experimented with early barcode systems to make ZIP codes machine-readable, but these efforts were limited in scope and capability. |
What the USPS needed was a system that could encode ZIP code information in a format that high-speed sorting machines could read reliably. The solution had to be simple enough to print on ordinary envelopes, robust enough to survive the rigors of postal handling, and compact enough to fit within the limited space available on a mailpiece. |
The inspiration came from an unexpected source: the supermarket checkout counter. The Universal Product Code (UPC) was becoming widespread in American supermarkets, enabling cashiers to scan items at unprecedented speed. The USPS saw the potential of similar technology for mail sorting and began developing its own postal barcode system. |
The result was PostNET, the Postal Numeric Encoding Technique. Introduced in the early 1990s and fully deployed by 1993, PostNET represented a major leap forward in postal automation. |
|
PostNET: The Numeric Encoding Technique |
How PostNET Works |
PostNET is a two-state barcode symbology. Unlike retail barcodes that encode data through varying widths of bars and spaces, PostNET uses bars of uniform width but two distinct heights. A tall bar represents a logical '1,' while a short bar represents a logical '0'. |
Each digit in PostNET is represented by a group of five bars. Within each group, two bars are tall (representing '1') and three bars are short (representing '0'). This five-bar pattern encodes one of ten possible digits (0 through 9). |
|
The encoding table for PostNET is elegant in its simplicity: |
The digit 1 is encoded as 00011, digit 2 as 00101, digit 3 as 00110, digit 4 as 01001, digit 5 as 01010, digit 6 as 01100, digit 7 as 10001, digit 8 as 10010, digit 9 as 10100, and digit 0 as 11000. |
Each PostNET barcode begins and ends with a 'frame bar'---a tall bar that marks the boundaries of the code. Following the start frame bar come the data bars representing the encoded ZIP code, then a check digit, and finally the end frame bar. |
The check digit is a crucial element of the PostNET system. It is calculated from the numeric data in the barcode and allows the sorting machine to verify that the code has been read correctly. If the check digit does not match the calculation based on the data, the machine knows an error has occurred and can either reject the mailpiece or attempt to read the barcode again. |
|
Data Capacity and Encoding Lengths |
PostNET could encode ZIP codes in three different lengths: 5 digits, 9 digits (ZIP+4), or 11 digits (ZIP+4 plus delivery point). The length of the barcode depended on the level of address specificity required. |
A 5-digit PostNET barcode encoded a basic ZIP code, such as 90210. This was sufficient for sorting mail to the level of a postal delivery area. |
A 9-digit barcode added the four-digit extension of the ZIP+4 code, providing more precise routing information. This allowed sorting machines to direct mail to more specific delivery routes. |
An 11-digit barcode added two additional digits representing the delivery point---typically the last two digits of the street address or a similar identifier. This enabled sorting to the level of an individual delivery point, such as a specific building or mail stop. |
The inclusion of delivery point information was a significant advancement. It meant that mail could be sorted not just to the correct postal facility or carrier route, but to the precise sequence in which the carrier would deliver it. This reduced the time carriers spent sorting mail before their routes and allowed them to spend more time actually delivering. |
|
The Physical Characteristics of PostNET |
PostNET barcodes are printed in a specific orientation, typically with the bars extending vertically from the bottom of the address block. The USPS established detailed placement requirements to ensure that PostNET barcodes could be read reliably by sorting machines. |
The barcode must be positioned within a 'clear zone' on the mailpiece, free from other printing or obstructions. Minimum clearances are specified between the barcode and the edges of the mailpiece, as well as between the barcode and other address information. For window envelopes, additional requirements ensure that the barcode remains readable even if the insert shifts within the envelope. |
The physical dimensions of PostNET bars are also carefully specified. The height difference between tall and short bars must be sufficient for the sorting machine's scanner to distinguish them reliably. The bars must be printed with adequate contrast against the background, and the printing quality must be consistent enough to avoid misreads. |
|
PostNET in Action: The Sorting Process |
When a mailpiece with a PostNET barcode entered the postal system, it was directed to a high-speed sorting machine. The machine would scan the barcode, decode the ZIP code information, and use that information to route the mailpiece to the appropriate destination. |
The machine could operate at remarkable speeds. Sorting machines equipped with PostNET readers could process up to 30,000 mailpieces per hour. This represented a dramatic increase in efficiency compared to manual sorting or even earlier automated systems. |
The postal sorting process involved multiple passes through sorting machines. On the first pass, the machine would read the barcode and sort mail to the appropriate sectional center facility (SCF). On subsequent passes, the mail would be sorted to finer levels of detail---to specific post offices, carrier routes, and finally to delivery sequence. |
The check digit in the PostNET barcode served as a quality control mechanism. If the scanner could not read the barcode or if the check digit indicated an error, the mailpiece would be diverted for manual processing. This ensured that even if a barcode was damaged or poorly printed, the mailpiece still had a chance of being delivered. |
|
PLANET: Tracking the Mail |
The Evolution from PostNET to PLANET |
While PostNET was highly effective for sorting mail, it did not provide any capability for tracking individual mailpieces. Once a piece of mail entered the postal system, the sender had no way of knowing where it was or when it would be delivered. For most mail, this was acceptable---standard correspondence and advertising do not require real-time tracking. But for time-sensitive communications or for mailers who needed confirmation of delivery, the lack of tracking was a significant limitation. |
The USPS addressed this gap with PLANET (Postal Alpha Numeric Encoding Technique), introduced as a complementary system to PostNET. While PostNET was designed for sorting, PLANET was designed for tracking and delivery confirmation. |
|
The PLANET System |
PLANET used the same two-state encoding technique as PostNET---tall bars for '1' and short bars for '0'---but it encoded different information. Where PostNET encoded ZIP codes, PLANET encoded tracking identifiers that could be associated with specific mailpieces. |
A PLANET barcode typically consisted of a frame bar, a two-digit service type identifier, a subscriber ID assigned by the USPS, data fields for mailer-defined information, a check digit, and an end frame bar. The structure of the barcode varied depending on the specific tracking service being used. |
PLANET was the barcode component of the USPS Confirm service, which allowed mailers to track their mail through the postal system. Two service types were available: Destination Confirm for outgoing mail and Origin Confirm for incoming reply mail. |
Destination Confirm provided tracking data as mail moved through the postal system toward its destination. Mailers could see when their mail had been processed at key points along the delivery route. |
Origin Confirm was used for reply mail. When a customer returned a reply card or other response, the Origin Confirm barcode allowed the mailer to track the response back to its origin. |
|
How PLANET Tracking Worked |
The mechanics of PLANET tracking were relatively straightforward. The mailer would print a PLANET barcode on each mailpiece, associating the unique identifier in the barcode with information about that piece of mail in a database. When the mailpiece passed through a postal facility equipped with PLANET readers, the barcode was scanned and the location and time were recorded. |
This information was made available to the mailer through the USPS Confirm service. Mailers could log into the system and see the status of their mailpieces at various points in the delivery process. For large mailers sending millions of pieces, this provided valuable intelligence about delivery performance. |
The tracking capability of PLANET was particularly valuable for time-sensitive mailings. A bank sending credit card statements, for example, might use PLANET to confirm that the statements had been delivered on schedule. A catalog retailer might use PLANET to track when catalogs were delivered, helping to correlate delivery with subsequent orders. |
PLANET also had applications beyond the Confirm service. The unique identifier in the PLANET barcode could be linked to customer information, enabling mailers to identify which customers had responded to a particular mailing. This was valuable for direct marketing, where understanding response rates is critical to measuring campaign effectiveness. |
|
The Limitations of PLANET |
While PLANET represented a significant advancement, it had limitations. Like PostNET, it was a two-state barcode with limited data capacity. The barcode could encode only a relatively small amount of information, which restricted its use to simple tracking identifiers. |
More significantly, PLANET was a separate system from PostNET. A mailpiece could bear both a PostNET barcode for sorting and a PLANET barcode for tracking, but this required additional printing and consumed valuable space on the mailpiece. Having two separate barcodes also increased the complexity of the postal processing system. |
The need for a more integrated solution was becoming apparent. The USPS needed a single barcode that could handle both sorting and tracking, with enough data capacity to encode all the necessary information. This led to the development of the Intelligent Mail Barcode (IMb). |
|
The Transition to Intelligent Mail Barcode |
A Unified Approach |
The Intelligent Mail Barcode (IMb), introduced in the mid-2000s and fully replacing PostNET and PLANET by 2013, represented a fundamental redesign of USPS barcode technology. |
Rather than the two-state system of PostNET and PLANET, the IMb uses a four-state approach. Each bar in the IMb can be in one of four distinct states: a short bar centered vertically (Tracker), a short bar aligned to the bottom (Descender), a short bar aligned to the top (Ascender), or a tall bar spanning the full height (Full). This four-state encoding allows significantly more information to be packed into the same physical space. |
The IMb encodes up to 31 digits of data in 65 bars. The data fields include a barcode identifier, a service type identifier, a mailer ID (either 6 or 9 digits depending on the mailer's volume), a serial number for tracking individual mailpieces, and a routing code representing the ZIP code. This comprehensive data structure enables the IMb to serve both the sorting function of PostNET and the tracking function of PLANET in a single barcode. |
|
The Benefits of the Intelligent Mail Barcode |
The transition to the IMb brought numerous benefits. For the USPS, it simplified the processing system by eliminating the need to read two separate barcodes. The IMb can be read by high-speed sorting machines, and the integrated data structure allows the USPS to sort and track mail simultaneously. |
For mailers, the IMb provided enhanced tracking capabilities. The unique serial number in each IMb allows mailers to track individual mailpieces through the postal system with greater precision than was possible with PLANET. This enables improved visibility into delivery performance and better customer service. |
The IMb also offers improved error detection. The barcode includes a CRC checksum that allows the system to verify the integrity of the read data. This is similar to the check digit in PostNET but provides more robust error detection. |
The IMb is part of a broader suite of Intelligent Mail barcodes that includes tray labels and container labels. The tray label, for instance, encodes information about the contents of a tray of mail, enabling automated handling of mail containers throughout the postal system. This integrated approach extends the benefits of barcode automation from individual mailpieces to the entire mail processing ecosystem. |
|
Industry Applications of PostNET and PLANET |
Postal Operations |
The primary application of PostNET and PLANET was within the USPS itself. These barcodes were essential infrastructure for postal operations, enabling the automation of sorting and tracking on a massive scale. |
PostNET was critical for achieving the levels of efficiency required to handle billions of pieces of mail annually. Without automated sorting, the USPS would have needed vastly more labor to process the same volume of mail, with correspondingly higher costs and slower delivery times. |
PLANET provided the tracking capability that businesses and other mailers needed for time-sensitive communications. The Confirm service, powered by PLANET barcodes, gave mailers visibility into the postal system that had previously been unavailable. |
|
Direct Mail and Marketing |
The direct mail industry was a major beneficiary of PostNET and PLANET. Direct mail campaigns often involve sending millions of pieces of mail to targeted audiences. The ability to automate sorting was essential for keeping postage costs manageable, as mail sorted to finer levels of detail qualifies for lower postage rates. |
PostNET enabled direct mailers to achieve these postal discounts by printing barcodes on their mailpieces that encoded the delivery point information needed for automation sorting. This was a significant cost savings that made direct mail more competitive as a marketing channel. |
PLANET added value by enabling tracking of response mail. When direct mail campaigns include reply cards or other response mechanisms, PLANET barcodes on those reply pieces allow the mailer to track responses back to the original campaign. This provides valuable data on campaign effectiveness and helps refine targeting for future mailings. |
|
Financial Services |
The financial services industry also made extensive use of postal barcodes. Banks, credit card issuers, and other financial institutions send millions of statements and notices by mail each month. The timely delivery of these communications is critical for regulatory compliance and customer service. |
PostNET ensured that these mailpieces were sorted efficiently and delivered on schedule. PLANET provided tracking for critical communications, such as notices of account changes or regulatory disclosures. The ability to confirm delivery of these communications provided a degree of legal protection for financial institutions. |
In some cases, financial institutions used PLANET tracking to confirm when checks or other negotiable instruments had been delivered. This information was valuable for managing cash flow and for resolving disputes about payment timing. |
|
E-commerce and Retail |
The rise of e-commerce in the 1990s and 2000s created new demands for postal tracking. Online retailers needed to confirm that orders had been delivered, both to satisfy customers and to manage inventory and accounting. |
While PLANET was not designed for parcel tracking in the same way as carrier systems like UPS or FedEx, it did provide some tracking capability for mailpieces that fell within the USPS mailstream. For e-commerce orders shipped via USPS, PLANET offered at least some visibility into the delivery process. |
The transition to the Intelligent Mail barcode has significantly enhanced tracking capabilities for e-commerce, with the unique serial number enabling more granular tracking of individual mailpieces. |
|
The Legacy of PostNET and PLANET |
Technical Influence |
PostNET and PLANET may no longer be in active use, but their technical legacy persists. The two-state encoding approach used by these systems influenced later barcode development, and the practical experience gained from their deployment informed the design of the Intelligent Mail barcode. |
The IMb itself is essentially a superset of PostNET and PLANET. It encodes the same types of information---ZIP codes for sorting and tracking identifiers for mail visibility---but in a more efficient and integrated format. The transition from two-state to four-state encoding reflects the trend in barcode technology toward higher data density and greater functionality. |
|
Lessons for Automation |
The story of PostNET and PLANET offers lessons for automation in any domain. The USPS recognized a problem---the need for faster, more accurate mail sorting---and developed a practical solution that could be implemented at scale. The solution was not the most technically sophisticated possible, but it was robust, reliable, and cost-effective. |
The incremental nature of the development is also instructive. PostNET came first, addressing the most pressing need for sorting automation. PLANET followed later, adding tracking capabilities that were not initially essential but became increasingly valuable. Finally, the Intelligent Mail barcode integrated both functions into a unified system. |
This progression suggests that automation often proceeds in steps, with each step building on the achievements of the previous one. Early adopters may need to accept simpler solutions that deliver immediate benefits, with the understanding that more sophisticated systems will follow. |
|
The Bigger Picture of Postal Barcodes |
PostNET and PLANET are part of a larger story of postal barcodes worldwide. Many national postal services have developed their own barcode systems, each tailored to the specific needs of their operations. |
The Royal Mail in the United Kingdom, for example, uses a system called Mailmark, which is based on a 2D barcode format rather than the linear barcodes used by the USPS. Mailmark can encode address information, a unique identifier, and mail class details in a compact format. Like the Intelligent Mail barcode, Mailmark supports tracking and sorting functions in a single barcode. |
The Australia Post and other postal services have also developed their own barcode systems, reflecting the diverse approaches taken to mail automation around the world. |
|
Conclusion |
Summary of Key Points |
PostNET and PLANET represent a crucial chapter in the history of postal automation. PostNET, introduced in the early 1990s, brought high-speed automated sorting to the United States Postal Service, enabling the processing of mail at rates previously unimaginable. Its simple two-state encoding---tall bars for '1' and short bars for '0'---proved robust enough for the rigors of postal handling and efficient enough for high-speed scanning. |
PLANET, building on the same two-state approach, added tracking and delivery confirmation capabilities. The Confirm service, powered by PLANET barcodes, gave mailers visibility into the progress of their mail through the postal system, supporting applications ranging from direct marketing to financial services. |
Both systems were ultimately replaced by the Intelligent Mail Barcode (IMb), a more sophisticated four-state symbology that integrated the sorting capabilities of PostNET with the tracking capabilities of PLANET. The IMb represents the culmination of lessons learned from its predecessors, encoding more information in less space while supporting a wider range of postal services. |
|
The Broader Significance |
The story of PostNET and PLANET is more than a technical footnote. It is a case study in how technology can be applied to solve practical problems at scale. The USPS faced a challenge that was both simple---sorting mail by ZIP code---and complex, given the vast volumes involved. The solution was not a single breakthrough but a series of refinements, each building on what came before. |
The experience of the USPS with postal barcodes also illustrates the importance of standards and interoperability. PostNET and PLANET were not merely technical specifications; they were components of a broader system that included printing equipment, sorting machines, and the USPS's internal processes. The success of the system depended on all these elements working together. |
The transition to the Intelligent Mail barcode also shows how systems evolve. The IMb did not represent a radical break with the past but rather a natural progression from the two-state systems to a more capable four-state format. The underlying principles---machine-readable encoding, check digits for error detection, standardized placement on mailpieces---remained largely unchanged. |
|
Looking Forward |
The Intelligent Mail barcode is now the standard for USPS automation, but even this system will likely be superseded at some point. The trend in barcode technology is toward greater data capacity and more sophisticated encoding, and emerging technologies like 2D barcodes and RFID offer capabilities far beyond what is possible with linear barcodes. |
Yet the legacy of PostNET and PLANET will endure. These systems demonstrated the transformative power of barcode automation, proving that machine-readable codes could handle the demands of a national postal system. The principles they established---reliability, speed, error detection, and integration with physical processes---remain as relevant today as they were decades ago. |
For those interested in the history of technology, the story of PostNET and PLANET offers insights into how innovations emerge, mature, and eventually give way to successors. It is a story of practical problem-solving, incremental improvement, and the relentless pursuit of efficiency. |
|
For those engaged with barcode technology today, the legacy of these systems is present in the Intelligent Mail barcode and other postal symbologies around the world. The lessons learned from PostNET and PLANET---about design, deployment, and the importance of standards---continue to shape the development of barcode technology in the postal sector and beyond. |
cs@easiersoft.com