A potentially very important development in motorcar technology is the autonomous vehicle (AV). Many anticipate that the development of a successful driverless car might lead to numerous changes in the operation of road networks and in travel behaviour, mitigating the adverse consequences associated with conventional vehicles, in particular crash deaths and injuries, and delays due to road traffic congestion.

There are many books, articles and op-eds on the practicalities and prospects for AVs. In this chapter, I will outline the key features of the technologies involved and how the safety of AVs would need to be regulated (cf. Lipson & Kurman 2016; Herrmann, Brenner & Stadler 2018). I will then focus on their impact on road traffic congestion, the most difficult challenge for surface transport operations.

Two routes to the development of vehicle automation are being pursued: evolutionary and revolutionary. The evolutionary route is being followed by the main vehicle manufacturers. Many anticipate that this involves developing a number of operational modes to assist the driver (known as advanced driver assistance systems, ADAS), such as adaptive cruise control, lane change assistance and automatic parking. These are generally introduced for high-end models and gradually move down the product range to mass-market models, costs reducing as scale of production increases and so more drivers gain experience of these feature. As more such systems are integrated, the role of the driver is reduced, with full automation the possible ultimate development. Before that point, there remains a role for the driver in circumstances where the automation cannot cope with road and traffic conditions. The potential difficulty of handing over to a human driver is the motivation for the revolutionary approach in which there is no role at all for a human driver.

Vehicle automation is very much in the developmental phase at present. The long-term prospects are far from clear. In this respect it is different from the technologies discussed in the previous chapters whose market prospects and societal impacts are considerably more evident. So I will first discuss the underlying technologies, since their scope for development and integration will determine the practicalities of AVs.