The canton wants to find out if the autonomous SmartShuttle buses will be useful for short journeys to certain tourist attractions such as the ‘Heidi village' in Maienfeld, PostBus told news agency ATS on Monday.
Tests will start on Wednesday, before the 11-seater buses welcome their first passengers on Friday.
Switzerland's first driverless buses launched in Sion's Old Town in June 2016.
Displaying the yellow livery of PostBus, the electric vehicles are installed with fleet-management technology developed by Lausanne start-up Best Mile which allows them to navigate roads accurately at a speed of 20km/hr.
Sion's trial was suspended in September 2016 after one of them suffered a minor collision, but the project later restarted. In October of this year the pilot phase was extended to at least December 2018 and the bus route lengthened by 1.5km to connect Sion rail station with the Old Town.
Though driverless, for safety reasons each bus has a conductor on board who can apply the emergency brake if necessary.