Back in August, a startup by the name of nuTonomy made headlines following the launch of the world’s first taxi service built around self-driving cars.

Albeit a trial only, the service, which covered a few streets in Singapore, provided an early look at a likely future where self-driving cars will be running around town offering rides. nuTonomy says a self-driving taxi service is much closer than most people think. In fact, the company says it hopes to launch the first fully functional service in Singapore as early as 2018.

Before that, nuTonomy will expand its test program to the United States. The company has signed an agreement with the City of Boston and the Massachusetts Department of Transportation that authorizes it to start testing its growing fleet of self-driving Renault Zoe electric cars on certain streets in Boston. (The company actually grew out of research conducted at nearby MIT.)

During the Boston road tests, which start later in 2016, nuTonomy’s self-driving system will learn local signage and road markings while gaining a deeper understanding of pedestrian, cyclist, and driver behavior and interaction across an urban environment much more complex than the one in Singapore. The system will also face more challenging weather conditions.

nuTonomy isn’t the only company developing such a service. Ride-sharing giant Uber is testing its own self-driving cars in Pittsburgh, Pennsylvania. The major automakers are also taking an active role. For example, General Motors Company [NYSE:GM] has teamed up with Uber-rival Lyft and could start its own autonomous ride-sharing service in Michigan in the near future. And Ford Motor Company [NYSE:F] in August said it will have an autonomous car ready in five years and may even be selling it to the public by 2025.