From a technological standpoint the main challenges for CPS applications for autonomous driving vehicles concern the development of autonomous navigation, map building and localisation and the ability to operate in a dynamic environment with a mixture of autonomous and non-autonomous vehicles and pedestrians. This requires reliable sensing technology in combination with viable deployment strategies. However, technology is one thing, there is also a need for societal acceptance and here the main requirement is to develop trust in autonomous cars. This can only be delivered through long-term successful demonstration of safe autonomous functionality to establish confidence. A key problem is that inevitably accidents will still happen. Here there is a need to educate people as it is clear that the media will pay particular attention to crashes of autonomous cars while not considering the overall improvements in safety provided by increasingly autonomous traffic. There are also other more practical barriers. For instance, there is a need for insurance companies to agree on an approach to apportioning liability before full autonomous functionality can be rolled out onto Europe’s roads. Security will also become an increasingly important issue as autonomous cars become highly interconnected. Systems need to be secure (no outside entity should be able to break into the system and cause an accident) but also there is a need for the vehicle to fail-safe even in the presence of a security breach. The obvious action in this case is to disable the engine and pull the vehicle over to the side of the road to a place of safety. Here designers will need to wrestle with the problems of providing security, privacy, and fail safe design to operate in presence of security breaches. With recent ransomware events the general population is becoming increasingly aware of the dangers of cyber-attack. Of course from a social standpoint there are likely to be concerns about entities disrupting traffic externally causing deliberate gridlock. In the future citizens may well believe that gridlock is a result of autonomous system failure or failure in intelligent traffic management systems, or even terrorist action. How will we know? So in the future it will be important to reassure drivers on their journeys that the traffic network is operating correctly and safely at all times – but how can we get them to trust us?