Cars which drive themselves without any intervention from a human operator have been legalised in the US state of Nevada.
The autopilot vehicles developed by Google were endorsed by means of a new legislation that removes all legal hurdles to the use of the technology.
The vehicles were tested on Californian roads, where they drove themselves thousands of miles with very limited human intervention.
A human was on board all the time, ready to take charge if there was a problem and also to meet the state's legal requirement for a driver to be nominally in charge at all times.
All the trips were accident-free except when a human-driven car hit one of the driverless cars.
A system where a convoy of drone vehicles tails a lead car driven by a human driver is being envisaged by Safe Road Trains for the Environment, an agency funded by the European Commission.
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