In testing on some live data, I did get one curious result. Consider this address:
541W 49 Street Apt 30 New York NY 10019 United States
The customer has attached the pre directional to the house number. SmartyStreets returned
541 W 49th St Apt 30W New York NY 10019-7164 United States
Which is pretty good, except that the apartment should be “30,” not “30W.” Our existing software, ZP4, got this right—I’m thinking that SmartyStreets may have assumed that the “W” was an attached secondary number like “D” in “403D Main St” or “403 Main St Apt D”. But in this case, doesn’t SmartyStreets have enough information in the USPS database to realize that the W isn’t valid on the secondary number and that the W got moved to the pre directional field?
In this case, the extra W on the end of the apartment number is unexpected but is still absolutely accurate. The official result from the USPS website is:
541 W 49TH ST APT 30W
NEW YORK NY 10019-7164
That extra W is a good question, so I looked into the other apartments in that building and the valid range of apartments is from 10 - 61 and they all have a W on the end (according to the US Postal Service). For some reason, the Postal Service has decided that the W designation is important to that address. Any company that uses USPS data to verify an address should always give back AT LEAST AS MUCH as the USPS does. I'm not sure why your previous software omitted the "W" on the end. I would guess that they are attempting to second-guess the address results from the USPS data. We prefer to enhance the USPS data rather than second-guess it, especially since they are the ones delivering the mail.