AM General, the firm best known for building Hummer H1s in both civilian and military versions, has been selected by a rather different governmental agency to help create a prototype with a different kind of civic duty in mind.

Postal trucks, those white boxes that deliver your mail, haven't changed in decades.

But that's all set to change.

DON'T MISS: USPS 'Long Life' Vehicles Last 25 Years, But Age Shows Now

AM General announced that it was one of six automakers selected to build a series of prototypes for the United States Postal Service.

While details of the new postal carrier vehicles are a long way off, AM General says that an emphasis on reducing vehicle weight will help it achieve fuel economy targets.

An "advanced powertrain option with system options" is also part of the plan, which probably means that the government will have the opportunity to evaluate hybrid and electric powertrains.

Renault 'HyKangoo' electric delivery van with Symbio FCell hydrogen fuel-cell range extender

Renault 'HyKangoo' electric delivery van with Symbio FCell hydrogen fuel-cell range extender

AM General says that their vehicle will need to be capable of sustaining a 20-year life in service—and, presumably, one that involves a tremendous amount of stop-and-go driving between mailboxes.

You may have seen a change in what your postal carrier has been driving; USPS recently bought a whole bunch of Ram ProMaster vans from FCA, but they're probably a little oversized compared to what AM General will whip up.

CHECK OUT: Hydrogen As Electric-Car Range Extender? French Tests Start Soon (Dec 2013)

Whether the USPS will be as technically adventurous as the French postal service in its vehicle choices remains to be seen.

The French are in the third year of testing a Renault Kangoo ZE battery-electric small commercial van that has had a small hydrogen fuel-cell range extender added to lift its range over 100 miles.

Deutsche Post StreetScooter electric van prototype

Deutsche Post StreetScooter electric van prototype

The German postal service, meanwhile, acquired the electric-van startup StreetScooter in 2014 after debuting a van that company designed in 2012.

This year it will put 2,000 of the electric vans on the roads.

And officials of the German agency hope to replace Deutsche Post's 30,000-unit fleet of internal combustion vans with electric vehicles eventually.

READ THIS: Germans to build own unique electric vans for postal service

Finally, some trivia: AM General's South Bend, Indiana, assembly plant is now building Mercedes-Benz R-Class crossovers under contract for the German automaker.

But all of those are being shipped to China, where there's still demand for that big three-row vehicle. 

CORRECTION: An earlier version of this story misstated AM General's role in developing the prototypes for the USPS. AM General was one of six contractors selected to help build prototypes.

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