Most engineering solutions to road safety problems ? better brakes and suspensions, more crash-worthy cars, seat belts and helmets, longer sight lines ? etc assume no change in road user behaviour. Most regulatory safety measures such as speed limits assume voluntary compliance or, failing that, strict enforcement. Most safety training, whether skills training for motorists, or road crossing training for children assumes that the trainee will apply the lessons with sense and vigilance. Most signs warning of danger are put in place on the assumption that people will read them. All these assumptions are routinely confounded by risk compensation: whenever there is a perceptible change in the safety environment, but no change in propensity to take risk, there is a behavioural response. If a car is fitted with better brakes, drivers do not drive the same way as before and enjoy a wider margin of safety. They go faster, follow more closely, start braking later or drive with less vigilance. The potential safety benefit gets consumed as a performance benefit. The lecture will discuss the widespread denial of this phenomenon and its potential, if acknowledged, to create more civilized urban environments.

John Adams, professor of geography at UCL, was a member of the original board of directors of Friends of the Earth in the early 1970s and has been a participant in debates about transport planning and environmental risks ever since.

He has published widely on risk management issues both in specialist journals and the national press, and is a frequent contributor to radio and television programmes on these subjects. His publications include Risk and Freedom: the record of road safety regulation (TPP, 1985), Risk (UCL Press, 1995), and (with Michael Thompson), Taking Account of Societal Concerns about Risk, a report for the Health and Safety Executive (2002).