The Effect of Cognitive Impairment on Older Pedestrian Behaviour and Crash Risk

Pedestrians are an extremely vulnerable road user group and make up approximately 15 percent of all road fatalities and 12 percent of all serious injuries. A large proportion of pedestrian deaths and serious injuries involve older adults, who are more vulnerable because of age-related frailty. Given that many crashes involving older road users occur in complex situations, it is suggested that age-associated cognitive and functional limitations may play some role in crash causation. While most research on older road users has focussed on identifying those who may be at increased risk, there is a lack of knowledge with regard to the effect of functional impairment, particularly the types and levels of cognitive impairment, on performance and crash risk of older pedestrians. This report assesses the current state of knowledge in regard to the key issues affecting older pedestrian safety, particularly the effect of cognitive impairment on behaviour and crash risk. A distinction is made between normal age-related cognitive decline and cognitive impairment associated with medical conditions. The association between normal age-related cognitive decline and pedestrian performance and crash risk seems to be fairly moderate. In contrast, more substantial evidence was found of an effect of medical conditions that result in cognitive impairment on pedestrian performance and crash risk. This was particularly so for impairments associated with moderate to severe dementia, moderate to severe Parkinson's Disease, cerebrovascular disease (particularly stroke), and multiple sclerosis. The review highlighted the need for better knowledge with regard to the effect and extent of cognitive decline and impairment on pedestrian safety and provides a number of recommendations for research priorities. While there are obvious benefits of walking for health and well-being of individuals and the environment, and pedestrian travel is a major mode of transport, older adults are at increased risk of death and serious injury as pedestrians. Unless there is a good understanding of how cognitive decline and impairment contributes to crash risk of older pedestrians and development of appropriate countermeasures, the problems and risks associated with pedestrian travel will worsen in the coming decades.