A fully autonomous bus is now in regular service in Scotland. It still has employees, two in fact. But if this technology works out, the ultimate goal is probably to run buses with no employees on board. In wealthy countries, the cost of running a bus is mostly the cost of the driver, so in theory, if and when all the bugs are worked out, a driverless bus could be far more abundant, for a given operating budget, than buses with human drivers can be.
That will be wildly controversial. I have mixed feelings about it. But driverless rail transit has existed for decades, starting in Vancouver in 1985. The lack of a driver is why trains in Vancouver come every few minutes even late at night. In emergencies people like for there to be someone in charge, but the voices coming over the intercom from headquarters often have a better picture of the situation than an on-board employee does. Driverless buses would definitely be part of a world where security is based more on electronic surveillance, and like many people I have mixed feelings about that.
But if we end up in a world with abundant and affordable autonomous taxis — still a big if — it will be very hard for cities to function without autonomous buses. When we remove the hassle of traveling by private vehicle, and reduce the cost, everyone will want to do it, and a city simply doesn’t have room for that. The only other solution will be heavy decongestion pricing to make the affordable autonomous taxis less affordable, and/or bus lanes on every street so that buses effectively bypass autonomous-taxi congestion. That may be the answer, but in the long run I’d rather see public transit be abundant, so that everyone can go places quickly in a space-efficient way.