Using police data, 2012-2019, we examine the impact on street crime of introducing low traffic neighbourhoods in Waltham Forest, London. Overall, the introduction of a low traffic neighbourhood was associated with a 10% decrease in total street crime (95% confidence interval 7% to 13%), and this effect increased with a longer duration since implementation (18% decrease after 3 years). An even larger reduction was observed for violence and sexual offences, the most serious subcategory of crime. The only subcategory of crime that increased significantly was bicycle theft, plausibly largely reflecting increased cycling levels. There was no indication of displacement of any crime subcategory into adjacent areas.