California regulators recently voted to allow a broad expansion of robotaxi services in San Francisco despite fierce opposition from city leaders. Alphabet Inc.’s, Waymo and General Motors Co.’s Cruise can now offer paid driverless rides across San Francisco at any time of day and using an unlimited number of vehicles…

MarketWatch talked with Philip Koopman, a professor at Carnegie Mellon University who has researched driverless-car safety for more than 20 years, about safety and liability concerns and what’s next for robocars.

MarketWatch: It feels like we’ve been stuck for a while now on the verge of having cars capable of driving themselves everywhere. Can you hazard a guess when truly autonomous cars will finally be here?

Koopman: No one knows…I can tell you that there’s still a lot of work left, especially to get both reliability and safety at the same time. As they say in the computer world: The first 90% of the work takes 90% of the time. The remaining 10% takes the other 90% of the time.

I think the more important question is where this technology can be deployed in the near term that is useful and economically viable. Low-speed shuttles in uncomplicated environments, cargo hauling on quiet routes and possibly middle-mile trucking, if the routes are picked carefully, are all a lot closer to being able to scale up than a car that can drive anywhere in any conditions.