A public bus without a fixed route or destination has been set off in the Swiss city of Baden in the latest piece of conceptual art by twin brothers Frank and Patrik Riklin designed to boost social connection.

The 'Line 0' bus is intended to help passengers escape their hectic lives and normal routines and interact with each other and scenery along the way.

"It's just so unplanned and spontaneous. We sang on the bus, we talked to everyone, we turned on our phone flashlights in the tunnel – it was just amazing", said Baden resident Kathrin Kalt, who was among one of the first to ride the bus.

Frank Riklin said the bus was about giving up control. 

"Normally, we're used to getting from A to B as efficiently as possible, but here we're actually called upon to let go", he said.

Although most of the passengers had planned to take the Line 0, one elderly couple got on by mistake on the first day, Patrik Riklin said.

"They reacted with humor and experienced Line 0 as if by chance, not because they knew it was there, but because they got lost, and turned it into an adventure", he added, smiling.

The artistic experiment is the latest project from the Riklin brothers, whose previous efforts have included an open air bed without walls in the countryside, which they called the zero-star hotel.

Passengers will be able to board and leave the bus free of charge as it moves through the existing bus network without a set route-plan.

Rather than checking tickets, organizers will collect passengers' thoughts about the experience.

Tickets will be free during the three-week trial, with the Riklin brothers hoping to eventually roll out the bus service in other parts of Switzerland.