The electric PostBuses, which have no driver but do have a conductor, have been tested as part of a pilot project in the Valais city of Sion since June 2016 on a 1.5km route through the pedestrian Old Town.
But from Wednesday the buses took to a new route from the rail station to the Place du Midi, taking them through regular traffic for the first time, according to Valais paper Le Nouvelliste.
Able to carry 11 passengers and travelling at a speed of up to 20km/hr, the buses can navigate roads accurately, identify obstacles and read road signs thanks to technology developed by Lausanne-based start-up BestMile.
The shuttles are operated using a special fleet management system and can be stopped by a remote operator if required. The vehicles can also be stopped by the conductor applying an emergency brake.
The trial was temporarily suspended in autumn 2016 after one of the vehicles had a minor collision with a parked delivery van.
The buses are currently free to use and run from Wednesday to Sunday.
The new route was launched without a hitch on Wednesday, said the paper, however services were temporarily suspended on Thursday due to the adverse weather conditions, as snow hit the area.