After growing quietly for decades, the ‘Zone 30’ movement is finding its momentum in recent years. Indeed, the number of cities that have adopted a 30 km/h speed limit, or 20 mph (miles per hour) for Anglo-Saxon countries, in some urban areas is growing. The limit, which generally applies on urban roads with the exception of highways, is conceived not only as a tool to reduce the number of accidents and accident-related fatalities, but also as an opportunity to promote a new urban vision of soft mobility and rediscovery of public spaces.
 

When the ‘Zone 30’ and the ‘City 30’ came to be

The adoption of the first 30 km/h limitations dates back to the 1990s. Switzerland anticipated the updating of its traffic codes as early as 1989, and Zurich made the introduction of certain ‘Zone 30’ areas effective in 1991. In 1992, the Austrian city of Graz became the first ‘City 30’ to adopt the 30 km/h limit on all roads, with the exception of major arterial roads. 

50 and 30 km/h compared: the impact on longevity and health

Road safety
If the speed of a vehicle decreases, in the event of an accident the chances of survival increase (WHO data):

• at 30 km/h: 99% chance of survival
• at 50 km/h: 80% chance of survival

Air quality (and reducing consumption)
- peak CO₂ emissions at 50 km/h: 2.2g/s
- peak CO₂ emissions at 30 km/h <1g/s (Jesùs Casanova, Universidad Politecnica Madrid)

Under laboratory conditions, an internal combustion engine produces on average more pollutant emissions at 30 km/h than at 50, however several studies have verified that under real on-road conditions, the situation is different. The 30 km/h speed limit inhibits the so-called ‘stop-and-go’ driving style of continuous accelerating and braking. This limits fuel consumption, and, as a result, pollutant emissions including not only CO₂ but also particulate matter. 

Noise pollution
Compared to 50 km/h, noise emissions at 30 km/h are reduced by about 3 dB. A decrease that, for the Swiss Federal Office for the Environment FOEN, corresponds to a noise perception of about half of the traffic. It also decreases the phenomenon of noisy acceleration.
 

The broader objectives

• Improving the safety of pedestrians and in particular vulnerable groups such as children, the elderly and the disabled
• Promoting the adoption of soft-mobility means of travel, such as bicycles, and encouraging walking, leading to a reduction in car traffic
• Incentivising the vitality of the public space, encouraging people to stay on the streets also by redesigning spaces and street furniture that encourage people to stay
• Promoting a vision of public space where different means of transport coexist harmoniously
• Relaunching the proximity economy
   

The impact on travel time

The various municipalities adopting Zone 30 and City 30 schemes claim that the average speed is already below 30 km/h due to traffic (in Milan it is around 15 km/h). On the contrary, lowering the limit makes it possible to relieve traffic congestion, with an advantage in terms of flow, and to maintain the same speed among various means of transport. On the contrary, detractors argue that there are no sets to objectively assess the effects on travel time.
 

International institutions committing to 30 km/h

• United Nations (with the Stockholm Convention) 
• WHO
• European Parliament 
• European Commission
• OECD

The Italian forerunners

Cesena introduced the first Zone 30 areas on some roads in its municipality in 1998, recording in the following years a significant decrease in accidents (-46.09%). Olbia became the first City 30 in 2021. As of 1 July 2023, Bologna is the first Italian capital to become City 30: the limit will extend over the entire urban area, with the sole exception of the main thoroughfares, where it will remain 50 km/h. The new road signs, consisting of 500 new signs and 300 horizontal makings, aim to promote compliance with the new standard limit. The application of fines was introduced gradually with the aim of avoiding a punitive application of the new regulations. 
 

The adoption of Zone 30 and City 30 schemes in Italy

The other Italian capitals that have officially approved and are implementing a 30 km/h limit throughout the city are: 

• Milan
• Padua
• Lodi
• Modena

Many other cities have already introduced Zone 30 or are starting experiments and participatory consultations to establish stages and modalities of a possible roadmap (Bergamo, Ferrara, Reggio Emilia, Florence, Turin).
 

The adoption of Zone 30 and City 30 schemes in the world

Many cities have long since adopted a 30 km/h limit. These also include some capital cities:

• Madrid (from 2018 on 80% of city streets)
• Helsinki (from 2019)
• Brussels (from 2021)
• Paris (from 2021)

In May 2021, Spain voted for an amendment to the highway code to impose a 30 km/h limit in all urban centres with the exception of roads with two or more lanes.

According to surveys conducted in cities that have adopted Zone 30 for some time, a consensus prevails among citizens on the goodness of the standard.
 

The expert's opinion

“In Italy we do not yet have significant data, but we can look at foreign experiences,” suggests Matteo Dondé, architect, urban planner, expert in mobility planning and in the City 30 model. “Since the adoption of City 30, the need for mobility has increased a lot in Brussels, with 4 million more kilometres travelled, but car use has decreased by 15 per cent, and walking and cycling have increased by 5 per cent and 7 per cent respectively. Barcelona, with its superilla model, has not shifted car traffic to other areas of the city, but reduced it altogether. Finally, the Paris fire brigade recently stated that, since City 30 became operational, they are able to arrive at the point of emergency sooner.” 

“As far as fuel consumption is concerned, the study carried out in London for twenty Zone 30 areas shows great environmental benefits. It is true that at 50 km/h you consume less fuel than at 30 km/h, but only if the speed is constant: in Italian cities, data tell us that the average speed is 18 km/h made up of continuous accelerating and braking, to which, moreover, a higher consumption of tyres is due, which have a greater impact on particulate matter and therefore on health.”

"In addition to promoting safety and reducing pollution, the idea of City 30 is to redistribute public space fairly: in Italian cities, 80 per cent is dedicated to lanes and parking areas, and 20 per cent to the pavement. With City 30 we do not want to deny the car but, by making it go slower, recover space to have a wider pavement, urban greenery, children's playgrounds, seating for the elderly. Turning the street into what it has always been: a place for people, for meeting and socialising.”