Most of the rules should be obvious -- for instance, the vehicles must be insured and obey the UK's normal road laws. Even in an automated mode, however, the supervisor should adhere to the same rules as an active driver -- that means they can't use their phone or anything else that might distract them. The Code of Practice also suggests alerting the highway authorities to testing zones and setting up a specialised contact with the local police and fire services. Finally, driverless cars should capture and store data while they're out on the road. Similar to a plane's flight recorder, this will give researchers and investigators a way to determine what went wrong after an accident or mechanical failure.

The Code of Practice shouldn't trouble the trials already underway in the UK. Most of the prototype vehicles haven't been designed for public roads anyway -- the Lutz pod and Meridian shuttle are gliding around parks and other pedestrian spaces, for instance -- but it lays the groundwork for when researchers are ready to tackle the open road.

To coincide with today's release, the UK government is opening up a fifth of the £100 million investment announced in George Osborne's March budget statement. The DfT says it's looking for projects that can improve the safety, reliability and awareness of driverless cars, as well as new research examining how such vehicles could be used to help elderly people. The investment is, however, dependent on bidders match-funding projects with their own money -- so only companies with deep pockets should probably apply.