A postal carrier route is a group of addresses that receive the same USPS code to aid in efficient mail delivery. Essentially carrier routes are further breakdowns of zip codes. Within each zip code there are many carrier routes. Carrier routes are the routes that each postal carrier delivers to daily on their mail delivery route. Carrier routes, on average, have around 500 addresses in them. However, some have much less and some have more. Mailing by carrier route allows you to strategically choose the areas that you would like to target without having to mail to an entire zip code.