Barcelona. Commuters in downtown Barcelona have been able to ride a bus for free this week—on one condition: there’s no driver.

Renault is testing an autonomous mini-bus on a 2.2-kilometer (1.3-mile) circular route with four stops in the city’s center. The vehicle, which operates without human intervention, smoothly pulls away from stops, brakes before changing lanes, and navigates one of Barcelona’s busiest boulevards.

The French automaker partnered with WeRide, a company specializing in autonomous driving technology, to develop the prototype. First unveiled at the French Open venue last year, the bus is now being tested in real-world conditions. Renault is also conducting trials in Valence, France, and at Zurich Airport.

Pau Cugat, an 18-year-old student, was among the curious commuters who stepped aboard for a short trip along Passeig de Gracia.

"We just passed a regular, combustion-engine city bus, and I thought, 'Look, there's a bus of the past, and right behind it, the bus of the future,’” he said.

Autonomous taxis and buses are being tested in cities worldwide, from San Francisco to Tokyo. However, Europe has generally lagged behind the United States and China in developing and deploying driverless technology.

“The U.S. is doing a lot of experimentation with autonomous vehicles, and the same is happening in China,” said Patrick Vergelas, head of Renault’s autonomous mobility projects. “In Europe, we haven’t seen much yet. That’s why we want to demonstrate that this technology works and help prepare Europe for the future of public transportation.”

The electric mini-bus is designed to travel up to 120 kilometers (75 miles) on a single charge and can reach speeds of 40 kilometers per hour (25 mph). It is equipped with 10 cameras and eight lidar sensors, which allow it to detect and respond to obstacles, pedestrians, and other vehicles in real time. Renault says the bus is capable of safely maneuvering through a congested urban environment like Barcelona.

The introduction of driverless vehicles into public transportation systems is seen as a potential game-changer, offering solutions for cities dealing with congestion, emissions, and labor shortages in the transport sector. Proponents argue that autonomous buses could improve efficiency and accessibility while reducing operational costs.

Still, the rollout of such technology faces challenges, including regulatory hurdles, safety concerns, and public acceptance. Many people remain skeptical about the reliability of self-driving vehicles, particularly in unpredictable city traffic.

Carlos Santos, of Renault’s autonomous driving group, said that reactions from passengers during the test phase have been varied.

“We’ve seen all kinds of responses—some people smile, others are amazed, take photos, or even try to open the doors,” he said. “But the ride is completely safe.”

Barcelona city officials confirmed that there have been no reports of accidents involving the experimental bus so far.

As the trial continues, Renault hopes that projects like this will help pave the way for greater adoption of autonomous public transport in Europe and beyond.