The company also envisages introducing a fleet by 2022 to overcome driver shortages, according to the agency.
Earlier in the day, Japan Post held a ceremony at its headquarters in Tokyo where it introduced a self-driving red car with the company's logo.
During the ceremony, Japan Post President Kunio Yokoyama said that it was the company's "social responsibility" to offer sustainable delivery services, adding that the introduction of self-driving vehicles was a "pressing agenda."
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The exact date of the trial remains unknown.
In recent times, Japanese companies have been actively participating in self-driving vehicle trial projects. In August, the Japanese authorities said that self-driving taxis might be used during the 2020 Summer Olympics in Tokyo.