The first-generation of vehicle-highway automation envisages automated vehicles operating on existing roads with no extensive infrastructure modifications required. Most of the required intelligence will be built into vehicles rather than the infrastructure. These vehicles will operate at spacings closer than commuter flows of today, with traffic flow benefits achieved through vehicle-cooperative systems as well as vehicle-infrastructure cooperation. See Coordinated Vehicle Highway Systems
Automated vehicles may cluster in 'designated lanes' which are also open to normal vehicles, or may be allowed on high-occupancy vehicle (HOV) lanes to increase their proximity to one another – to realise the benefits of cooperative operations. Stabilisation of traffic flow and modest increases in capacity are seen as the key outcomes.
Once this level of functionality is proven and in broad use, a second generation scenario comes into play which expands to dedicated lanes, presumably desired by a user population with a high percentage of automation-capable vehicles.
With growing use, networks of automated vehicle lanes would develop, offering the high levels of per-lane capacity achievable through close-headway operations where vehicles are closely spaced. However, this type of evolution may take a while. First generation automation for passenger vehicles and trucks is already here, with estimates for second-generation implementation in prospect.
The key technical challenges that remain to be mastered involve software safety, system security, and malfunction management. The non-technical challenges are issues of liability, costs, and perceptions. See Legal and Regulatory Issues, Contracts and Engagement with ITS. It is also important to recognise that automated vehicles are already carrying millions of passengers every day. Many major airports have automated people movers that transfer passengers among terminal buildings. Modern commercial aircraft operate on autopilot for much of the time, and they also land under automatic control at suitably equipped airports on a regular basis.
In the long term it seems unlikely that technological difficulties will hinder the widespread introduction of intelligent vehicles and highway systems. It is more likely to be a sceptical and wary public that is the barrier to acceptance. How will humans cope with increased automation of the driving task? Who wants to share the road with a convoy of 40-tonne driverless lorries? Or are we heading towards the time when human driving will become a form of extreme sport to be allowed only within controlled areas?