Until recently, the absence of a local or national directory was a limiting factor for use of multi-line OCRs. However, in the 1981-83 period, USPS completed a national ZIP+4 directory and local ZIP+4 directories for major metropolitan areas. The national directory is stored on a computer in San Francisco and is essentially the sum of all local directories.
In the four cities where multi-line OCRs are already operating (Chicago, New York, Philadelphia, Dallas), the local directories have been partially converted to a format usable by the multi-line OCRs. For example, the Philadelphia multi-line OCR uses a converted local ZIP+4 directory containing about 185,000 local ZIP+4 codes covering more than one-half of the addresses in the Philadelphia metropolitan area.
USPS and OTA agree that the conversion of existing local ZIP+4 directories to a multi-line OCR format is technically feasible. This would be simply an extension of the partial conversions already accomplished in the four cities noted above.
Whereas local directories clearly would be necessary for multi-line OCR operation,
OTA was not able to determine whether national directories would offer any significant
multi-line OCRs twice, once at the second time at the destination post would, in theory, eliminate the need
originating post office to the 5-digit level and a office to the 9-digit level. A national directory for two-stage OCR processing. After the initial
OCR processing, the ZIP+4 bar coded mail could be handled entirely by the less expensive bar code
bypass subsequent sorters.
USPS argues that this would not result in a reduction in the number of OCRs, since these machines would still be needed for processing outgoing mail at the destination post