BARCELONA, Spain (AP) -- Commuters in downtown Barcelona have been able to ride the bus for free this week. There's just one catch: this mini-bus has no one at the wheel.

The bus pulls away from the stop with its passengers on its own, brakes before changing lanes and eases down one of Barcelona's most fashionable boulevards.

Renault is testing a new driverless mini-bus in Barcelona this week. The autonomous vehicle is running on a 2.2-km (1.3-mile) circular route with four stops in the center of the Spanish city. Adventurous commuters can jump on free of charge.

The French carmaker has teamed up with WeRide, a company specializing in autonomous vehicles, to make the prototype. It unveiled the driverless bus at the French Open venue last year, but now it is testing it on the open road in Barcelona. It also has testing projects going in Valence, France, and at the Zurich airport.

Pau Cugat was one of the curious to step aboard for a short ride along Passeig de Gracia boulevard.

"We just passed by a regular, combustion-engine city bus, and I thought, 'Look, there is a bus of the past, and right behind it you have the bus of the future,'" the 18-year-old student said.

Driverless taxis and buses are being tried out by companies in other cities, from San Francisco to Tokyo.

But Renault's initiative comes as Europe generally lags behind the United States and China in driverless vehicle technology, where companies are fiercely competing to get ahead.

"The US is doing a lot of experimentation with autonomous vehicles, the same thing in China," Patrick Vergelas, head of Renault's autonomous mobility projects, told The Associated Press. "Until now we don't have a lot in fact in Europe. And this is why we want to show that this works and prepare Europe to this route in public transportation."

The electric bus can run for 120 kilometers without a recharge and reach 40 kilometers per hour (25 mph). It is equipped with 10 cameras and eight lidars (sensor arrays) to help it navigate the streets filled with cars, motorbikes and pedestrians. The company says the bus is able to drive safely on a given course through a busy downtown like that of bustling Barcelona.

Carlos Santos, of Renault's autonomous driving group, said that he has seen all types of reactions from riders.

"We've seen a lot of behaviors of people. Some of them were smiling, (while) other people just start crying, taking photographs or even try to open the doors," Santos said before he insisted that the bus ride was a safe one.

Barcelona's city officials said that they have had no reports of accidents caused by the experimental bus.