At a time of ever-increasing urbanization, research consistently indicates that crime and the fear of crime are key concerns for society and that safety is a vital feature of what is considered a high-quality sustainable environment. This paper critically inspects the theories and evidence from the field of environmental criminology and interrogates some of the safety assumptions underpinning planning policy in the UK, the USA, and in Australia, particularly those policies promoted by New Urbanism. It is argued that planning professionals need to consider and understand this new perspective for safer and sustainable cities, rather than relying on assumptions that are not supported by any systematic evidence.