The obvious answer would be when 100% of the vehicles on the road are smart.


But smart cars are paid for by their owners.  Roads are paid for by national and local government, who can't even afford to re-surface our roads regularly, let alone upgrade them all to smart roads.


In any case, would you want to be the person making repairs in the middle of the highway, protected from the oncoming traffic by nothing more than a wireless beacon?

Autonomous vehicles don't need 'smart' roads, that is what is so clever about them. For year engineers thought that 'the future' would be vehicles following a wire or similar technology but, as often happens, developments in other fields can suddenly make an old idea practicable or allow a completely new approach.


The idea of following a wire is amazing enough, imagine being able to determine one's position on Earth by radio signals from a satellite wizzing around the sky! Advances in imaging systems have also been amazing. Thirty years ago it was thought pretty smart to beam a line of light onto a conveyor belt and observe the 'kink' when an object intercepted the beam, now 'speed' cameras can pick out and read the number plates on cars 'anywhere' on the road, (not tracking a fixed line). All of this has been built on low-cost computing power in the application AND the design of these systems. That is the great thing about engineering and technology, nothing is wasted, we build on the past, we recycle ideas and we innovate.


As to 'smart' roads they do exist to some extent, unfortunately they require a lot of re-working for structures, telecomms and power systems. They cetainly could be 'smarter'. There surely must be some means of U-turning traffic safely when the 'powers that be' decide to close a motorway. It is ridiculous that in a developed country that vehicles and their passengers can be 'trapped' on a motorway for hours and that they can't be released via the empty opposing lanes. Maybe motorways should be managed by engineers not the police?