INTRODUCTION: Road crashes are a major social problem, resulting in 1.19 million fatalities and over 50 million injuries annually. Speeding is the primary cause of road crashes worldwide, particularly in cities where pedestrians, cyclists, and motorcyclists are especially vulnerable. This paper aims to review and assess the effectiveness of implementing a 30 km/h speed limit. METHOD: To achieve this objective, a comprehensive literature review was conducted, evaluating the impact of 30 km/h speed limits on safety, emissions, energy consumption, traffic flow, livability, and health. The systematic literature review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. RESULTS: Current scientific evidence indicated that the introduction of 30 km/h speed limits in cities can save over 40% of lives, alongside significant positive effects on the environment, energy consumption and public health, including reduced fuel consumption and increased walking and cycling. PRACTICAL APPLICATIONS: Public awareness campaigns and promoting the use of public transport and active mobility options, such as walking and cycling, could further support the adoption of 30 km/h speed limits in cities.