Sorting Letters Better

Letters account for the greatest amount of mail volume — about 73 percent in 2006 — so the Postal Service first focused on automating the processing of letters. In the 1990s, new generations of equipment and technology dramatically speeded up letter processing.

By 1989, multiline optical character readers had replaced single-line optical character readers, allowing equipment to read and barcode letters without a ZIP+4 code so this mail could be sorted on high-speed barcode sorters to the individual carriers who would deliver the mail. In 1991, BCSs were retrofitted so they could scan a wider area on a piece of mail to find the barcodes, essentially anywhere on the envelope face. This gave mailers more flexibility in designing their mail, placing their barcodes, and being able to barcode letters as they addressed them, saving mailers time as well. Previously, barcodes had been restricted to the lower right hand corner of each piece of mail.

In 1991, the Postal Service offered discounted rates to mailers who prebarcoded their mail, which then could bypass multiline OCRs, saving the Postal Service time and money — savings passed on to the mailers. These discounts helped the percentage of mail with customer-applied barcodes jump from just 7 percent in 1990 to 59 percent in 2000.

Throughout the 1990s, advanced facer-canceler systems (AFCSs) were deployed. These systems face (orient) and cancel 30,000 pieces of mail per hour — nearly twice as much as the older Mark II facer-cancelers they replaced. AFCSs sort mail by address type (script, barcoded, and machine imprinted) for routing to proper equipment. In 2002 and 2003, nearly one-third of AFCSs were modified with video facing units, which use images to orient letters, avoiding manual processing of letters which cannot be oriented in the normal way, that is, by looking for special ink in the stamp or postage area. Each major processing facility was given at least one of these enhanced AFCSs.

In 2005, all 1,086 AFCSs were given video facing units and were upgraded with OCRs so they could identify the five-digit destination ZIP Code on each letter. Advanced facer-cancelers were also upgraded with doubles detectors so the Postal Service could reduce rehandling mail that stuck together as it went through equipment. That same year, a switch was made to ink jet cancelers, which included a time stamp, allowed different messages, and were easier to use and maintain than previous mechanical cancelers.

To take letter mail processing to the next level — sorting it automatically to the customer level — the Postal Service lengthened the nine-digit ZIP+4 code by two digits in 1990. These additional digits represent specific addresses, called “delivery points.” First tested in 1991, barcodes representing these delivery points enable equipment to sort letters into trays in delivery order, so carriers can get out on the street to deliver mail more quickly. The Postal Service retrofitted existing equipment to sort mail to delivery points and, in late 1991, deployed the first delivery barcode sorters. Since then, the Postal Service has installed more than 8,900 delivery barcode sorters and carrier sequence barcode sorters (smaller units with a similar function used since 1995). By 1998, these machines had almost completely replaced the old multi-position letter sorting machines. Today, letter mail arrives in trays in the order of delivery to almost all city carriers and more than 75 percent of rural carriers.

The remote barcoding system, first tested in Tampa, Florida, in 1992, provides the Postal Service with a means to apply barcodes to mail that cannot be processed by multiline optical character readers (MLOCRs) when the print quality of an address is poor or the handwriting difficult to read. The MLOCRs were modified to include a video encoding feature that sends an image of an illegible address to a remote computer reader (RCR) or a data conversion operator at a remote encoding center, without removing the mail from the processing plant. Since 1996, advanced facer-cancelers have captured and sent images of handwritten addresses. If the RCR cannot decipher the address, an operator at the center reads the address and keys in the information so the piece can be barcoded for proper sorting.

The number of remote encoding centers peaked by 1997, when 23,000 employees at 55 centers nationwide keyed in address information to barcode about 24 billion letters. The number of centers began declining just two years later, in 1999, as more prebarcoded letters entered the mailstream. Better technology also had improved incrementally the address recognition rates of the MLOCRs and RCRs. For example, in 1997 MLOCRs received new gray scale cameras, and RCRs received new handwriting analysis software, which helped both machines decipher more addresses. In 1998, the Postal Service nationally deployed new software that enabled MLOCRs to read more than 50 percent of addresses. In 1999, for the first time, the number of MLOCR-generated barcodes exceeded the number applied by the remote barcoding system.

Between 1997 and 2003, the percentage of machine-readable handwritten addresses jumped from less than 2 percent to about 80 percent. Along with other advances, improved address recognition increased letter mail productivity in processing plants by nearly 50 percent from 1993 to 2001.

Since 2000, the Postal Service has worked to increase the thickness and weight of mail that can be processed on automation equipment. In 2000, the eight percent of letter mail that still had to be processed manually accounted for half of the labor cost for processing letters. That year, the Postal Service installed six prototype delivery barcode sorter expanded capability machines at three processing plants. Expanded capability machines process a wider range of letter mail, from flimsy to thick, heavy pieces, that postal workers previously sorted by hand. Carrier sequence barcode sorters received additional stackers in 2001 and 2002, allowing machines to sort to a greater number of delivery points on a route.

In 2000, the Postal Service also began to deploy state-of-the-art DIOSS systems (delivery input/output subsystem barcode sorters), an upgraded delivery barcode sorter. With up to 302 bins to receive mail — five times more than the equipment it replaced — DIOSS can provide a finer, more localized sort, reducing the number of handlings and accelerating delivery times. Around the same time, identification code sort systems were added to barcode sorters, so the machines could sort mail, if need be, using the fluorescent barcodes sprayed on the backs of envelopes by the remote barcoding system to identify mailpieces. This saved two additional passes through sorting machines to re-barcode mail when address barcodes were unreadable.

In 2005, the Postal Service completed deployment of more than 9,000 wide-field-of-view cameras, which replaced aging wide area barcode readers. The newer cameras read a barcode virtually anywhere on the front of an envelope as well as information-based indicia codes such as “electronic postage” and barcodes on certified mail.

In 2004, to increase its efficiency in handling undeliverable-as-addressed (UAA) letter mail, the Postal Service began deploying the postal automated redirection system (PARS) to processing plants nationwide. PARS automates the handling of UAA letter mail, reducing the number of times it needs to be handled and the costs of processing it by intercepting portions of this mail earlier in the sorting process. PARS also automates the processing of change of address forms and provides two revenue-generating services: electronic notification to mailers who subscribe to the address change service, and hard copy notification to mailers who add an endorsement to their mail.