In the United States, there are three types of mail carrier, all of whom walk varying distances each day depending on their location and the type of route they work. City mail carriers walk the most, because they tend to have small, localized routes. Rural mail carriers and highway contract route carriers walk less, because their routes are based in motor vehicles. City and rural mail carriers are official, unionized employees of the United States Postal Service. Highway contract route carriers are private contractors.

All mail carriers start their day by arriving at a sorting facility to pick up the mail for their routes. Sorting facilities divide the mail up first by zip code, and then by mail carrier routes. Within a zip code, there may be up to fifteen mail carrier routes, depending on density. Mail carriers further sort their mail, organizing it in the most effective way for their route. Many carriers work the same routes every day and become very familiar with their postal customers.

City mail carriers have walking routes and driving routes. In the case of a mail carrier on a driving route, the mail is loaded into a post office vehicle and driven out. Many cities require that mail carriers park in a central location and distribute mail from there before moving on to another centralized location, to avoid stopping and starting mail vehicles at each destination on the route. This cuts down on the potential for traffic accidents and runaway postal vehicles. Mail carriers on driving routes alternate several miles of walking with driving each day and may return to the mail facility for another load.

Mail carriers on walking routes usually cover the area closest to the mail sorting facility. In a major city with numerous postal facilities, there may be a large number of walking routes. Walking mail carriers load their mail either into shoulder bags or onto small hand-wheeled carts and may walk up to ten miles round trip to complete their mail deliveries.

Rural and highway contract route mail carriers base their routes almost entirely out of their vehicles, which may be privately owned vehicles specially modified for postal work or official post office vehicles. They do very little walking on their daily routes, as most rural routes position their mailboxes close to the road for easy access. These mail carriers are required to do some walking and heavy lifting while loading their mail for the day’s route.