This paper reviews the effectiveness of city-wide 30 km/h speed limits in European cities, focusing on safety, environmental, energy, traffic, and livability impacts. The study uses a quantitative approach and qualitative assessments to analyze data from 40 cities, including Brussels, Paris, and Zurich. Key findings include: 1. **Safety**: Implementing 30 km/h speed limits reduced road crashes by an average of 23%, fatalities by 37%, and injuries by 38%. These reductions are attributed to decreased crash risk and severity. 2. **Environment**: Lower speed limits led to a 18% reduction in emissions, a 2.5 dB decrease in noise pollution, and a 7% reduction in fuel consumption, enhancing fuel efficiency and environmental sustainability. 3. **Energy**: The implementation of 30 km/h speed limits resulted in a 7% decrease in fuel consumption, contributing to energy conservation. 4. **Traffic**: Speed limit reductions encouraged the use of active modes of transportation (walking, cycling) and public transit, leading to improved traffic flow and reduced congestion. 5. **Livability**: The initiative contributed to a safer and more livable urban environment, with reduced noise levels and improved public health through decreased obesity rates and increased physical activity. The study concludes that city-wide 30 km/h speed limits are effective in improving road safety, reducing environmental impacts, and enhancing urban livability. The findings support the implementation of such measures as a strategic approach to achieving the European Union's Vision Zero goal of zero road deaths and serious injuries by 2030.This paper reviews the effectiveness of city-wide 30 km/h speed limits in European cities, focusing on safety, environmental, energy, traffic, and livability impacts. The study uses a quantitative approach and qualitative assessments to analyze data from 40 cities, including Brussels, Paris, and Zurich. Key findings include: 1. **Safety**: Implementing 30 km/h speed limits reduced road crashes by an average of 23%, fatalities by 37%, and injuries by 38%. These reductions are attributed to decreased crash risk and severity. 2. **Environment**: Lower speed limits led to a 18% reduction in emissions, a 2.5 dB decrease in noise pollution, and a 7% reduction in fuel consumption, enhancing fuel efficiency and environmental sustainability. 3. **Energy**: The implementation of 30 km/h speed limits resulted in a 7% decrease in fuel consumption, contributing to energy conservation. 4. **Traffic**: Speed limit reductions encouraged the use of active modes of transportation (walking, cycling) and public transit, leading to improved traffic flow and reduced congestion. 5. **Livability**: The initiative contributed to a safer and more livable urban environment, with reduced noise levels and improved public health through decreased obesity rates and increased physical activity. The study concludes that city-wide 30 km/h speed limits are effective in improving road safety, reducing environmental impacts, and enhancing urban livability. The findings support the implementation of such measures as a strategic approach to achieving the European Union's Vision Zero goal of zero road deaths and serious injuries by 2030.