Research on the limitations of human vision has been influential in lowering speed limits to 20mph in residential areas, saving an estimated 38 lives and preventing over 450 serious injuries each year, and stimulating car technology innovation.


  • Professor John Wann's research was used extensively in a successful UK campaign by the nationwide campaign group 20's Plenty for Us to demonstrate the need for reducing urban speed limits, especially in residential areas with children. The campaign resulted in the adoption of 20mph speed limits for residential streets in 40 local authorities, comprising nearly 10 million residents (including Liverpool, Portsmouth, Bristol, York, Brighton, Bath, Newcastle, Oxford, Cambridge, Hackney).
  • Twelve other local authorities (including Birmingham, Wirral, Norwich) also made a commitment to implementing 20mph residential speed limits.
  • A large number of urban speed limits were reduced across North Lincolnshire as a result of Professor Wann giving evidence to a North Lincolnshire Authority transport select committee.
  • As a consequence of the speed limit reductions in these local authorities, it is estimated that 38 pedestrian lives are saved and over 450 serious injuries prevented each year (based on epidemiological research and Department for Transport pedestrian casualty figures for 2011).
  • A campaign citing the research was successful in saving 51 out of 61 school crossing patrols in Dorset from closure due to budget cuts.
  • Interactive computer-based demonstrations designed by Royal Holloway as part of an ESRC Knowledge Transfer project has been used by Road Safety Officers, Police and the Fire Service to provide road safety awareness to their drivers.
  • Software designed by the team has been used by Heathrow Airport Holdings Limited, the operators of Heathrow Airport, in their safety awareness programme, and delivered to their safety team who are responsible for over 20,000 drivers.
  • Due to his research Professor Wann sits on the scientific advisory committee for the QUADRA project at Volvo Technology, focusing on forward collision warning and lane departure software systems, and how drivers may interact with them. These systems have the potential to increase safety for hundreds of thousands of road users.
  • In 2017 Professor Wann began advising national agencies on changes to road infrastructure that could reduce errors in noticing other road users.
  • Research on motorbike light configuration has been used to provide advice to New Zealand bikers about the kinds of lighting configurations they can use to increase their safety.

"Wann's research was influential in providing evidence that children below secondary age cannot be relied upon to have the necessary visual acuity to manage their own safety in situations where vehicles are travelling above 20mph." (Rod King MBE, founder and Campaign Director of 20’s Plenty for Us)

About the research

Professor John Wann, a psychology researcher at Royal Holloway, University of London, has spent over a decade researching the human visual system and the role it has to play in road traffic accidents. His research explores the neural processes that underpin people's ability to detect approaching vehicles, and to determine their speed.

The research showed that children under 11 are unable to accurately judge the approach of vehicles travelling above 25mph, emphasising the need to reduce speed limits in areas where children are present. It also showed that adults over the age of 75 are poor at judging the speed of oncoming vehicles, making them more likely to make mistakes, particularly at A-road intersections.

Wann's research team partnered with the Transport Research Laboratory to look at the psychology behind people's detection of motorcycles. This research showed that at night-time people are less able to judge the speed of motorcyclists than they are cars, due to motorbikes only having one headlight. The team proposed a tri-light modification for motorbike headlights that could eliminate this problem – confirmed by a successful trial in New Zealand.