The U.S. Postal Service has awarded $37.4 million in contracts to six vendors to provide 50 prototypes of a next-generation delivery vehicle that will be tested in various climates and locales, the USPS has announced.

AM General, Karsan, Mahindra, Oshkosh, Utilimaster, and VT Hackney will have one year to develop and produce their prototypes.

While Fiat Chrysler Automobiles, Ford, Nissan, and Freightliner made the initial list of pre-qualified vendors, these larger vehicle manufacturers could partner with the final six as subcontractors to supply engines, transmissions, or other parts.

VT Hackney, a North Carolina body builder perhaps best known as a supplier to the beverage industry, will submit several prototypes in collaboration with Workhorse. The company will add a custom body to a modified E-Gen plug-in hybrid platform to build a truck with a GVW of about 6,500 pounds, which puts in on the lighter end of Class 2. The vehicle will include a back-up camera, said Richard Ball, VT Hackney's marketing and business development director.

Half of the prototypes will feature hybrid and new technologies, including alternative fuel capabilities. The prototypes will represent a variety of vehicle sizes and drive configurations, in addition to advanced powertrains and a range of hybrid technologies, according to a USPS statement.

Once the prototypes are delivered, the USPS plans to test the vehicles for about six months in different climates, topography, population centers and delivery environments. The tests will help demonstrate the ability of the proposed designs to meet operational needs, such as deliver to mailboxes.

The USPS has been reluctant to use an off-the-shelf cargo van because the seating is often too high and mail delivery personnel have to reach down toward the mailbox. Federal regulations require the bottom of the mailbox to be 42 inches from the ground. The vehicle must also be right-hand drive.

However, the USPS is planning to release a request for proposal for an off-the-shelf, right-hand drive vehicle to supplement its fleet as it "continues to assess the delivery fleet mix." The USPS has ordered 12,472 Ram ProMaster 2500 cargo vans in the past year.

The delivery of the prototypes represents the next step toward the deployment of the next-generation vehicle, which should begin rolling out in 2018. The USPS plans to replace as many as 180,000 carrier route vehicles for between $4.5 billion and $6.3 billion over as many as seven years.