Waymo’s vehicles are currently being operated by a safety driver, mapping the streets.
But when the service launches to paying passengers, there will be no human at the wheel.
Greenwood, who attended the Waymo event, said she expected driverless vehicles to make city roads safer.
“We know that unlike human drivers, automated vehicles don’t get tired, don’t get distracted and don’t drive under the influence,” she said.
But she added that autonomous vehicles also had to meet strict safety standards, “including protection from hacking and cyber threats” before they would be allowed on UK roads.
The government has estimated that the autonomous vehicle industry could add £42bn to the UK economy by 2035 and create nearly 40,000 new jobs.
Passengers will be able to hail Waymo robotaxis via an app once the rules permit.
They will not initially include airport drop-offs.
The Waymo vehicle uses four sensor systems to gather data from the world around it: lidar, vision, radar and microphone.
It claims these sensors enable its vehicles to be aware of its surroundings 360 degrees, as far as three football fields ahead and during bad weather.
A powerful computer in the boot processes that data and determines the cars actions and reactions in real time.
A Waymo spokesperson said pricing would be “competitive” but “premium” and would rise during periods of high demand.
