Story highlights Internet has hurt the postal service, but could also be its savior

Amazon could go to same-day shipping, and use U.S. Postal to do it

USPS has a pilot program, Metro Post, that does just that

It's the internet's fault that, if the U.S. Postal Service has its way, you won't be getting letters delivered to your mailbox on Saturdays anymore. After all, how many stamps have you bought lately?

But the engine of the USPS's demise could also save it. After all, how many packages have you received from Amazon lately? And wouldn't you like to get them faster?

Postal Service spokesman John Friess says that while its letter-carrying business is shrinking, its package-delivery business is growing. (Note that postal carriers will still be delivering packages on Saturdays.) In its anxious search to make money any way possible, the agency late last year began testing a same-day delivery service in San Francisco for online purchases. While the experiment, called Metro Post , is starting out small, it also comes at a time when the world's largest online retailer might be looking for a lot of trucks and a lot of drivers who can do same-day delivery cheap.

Amazon's strategy for consumer domination includes erecting million-square-foot warehouses near the country's largest cities. The company has played coy on whether its expanding physical infrastructure signals plans to offer same-day delivery on a wide scale. If so, it will still need a transportation infrastructure to go along with it.

And that fleet can't just consist of UPS trucks that Amazon tells to go faster. Same-day delivery requires a fundamentally different logistical framework from its standard system, logistics experts say. To get orders delivered even as quickly as overnight, Amazon pulls together the orders at its distribution centers before turning the packages over to UPS or FedEx. The carriers then feed those packages into their own logistics operations, which typically means traveling to UPS or FedEx distribution centers and depots before heading out on trucks to people's houses.

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All of that transit doesn't move fast enough for same-day. To make same-day work, the orders must travel straight from the distribution centers to customers.

Of course, Amazon could hatch plans with UPS and FedEx to offer same-day. Unlike those two companies, however, which both have thriving businesses doing what they already do, the USPS has drivers with fewer letters to deliver and a desperate need to innovate. According to the optimistic logic of the so-called sharing economy, that seemingly dire scenario doesn't look like a problem; it looks like idle capacity just waiting to be leveraged.

According to Friess, the Postal Service wouldn't need to hire new drivers or buy more trucks to offer same-day, Friess says. The agency would simply have to adjust where its drivers were going and when.

"We already have the existing infrastructure in place," he says. "That's what sets us apart."

The postal service still has miles to go before becoming Amazon's courier of choice. The pilot program is limited to delivering a maximum of 200 packages per day to customers of 1-800-Flowers.com's sister brands, which sell popcorn, cookies, chocolate and gift baskets. Friess says the USPS is planning to add more retailers soon. If the test is successful, which he says the agency believes it will be, Metro Post will roll out to other large markets across the country.

Friess declined to speculate on whether the USPS' 214,000 trucks — what the agency calls the world's largest civilian fleet — could end up in the service of Amazon.

But he said he believed the USPS will start to look increasingly attractive to other companies exploring the same-day option: "We'd never close the door on ways to expand our revenue."