TO Rome is triggered speed limit of 30 km/h in the historic center of the city: the capital thus follows the example of other Italian cities, such as Bologna And Milanwho in recent years have adopted this initiative to improve road safety, try to reduce road accidents and air pollution. But does introducing this speed limit really work? According to the EU Transport Safety Council (ETSC) report, 30 km/h represents the maximum threshold within which the coexistence between cars and vulnerable users (pedestrians and cyclists) is considered acceptable: in fact, accidents, noise pollution and particulate emissions decrease, although the risks are not eliminated, but the measure is truly effective when supported by urban strategies on a larger scale. So let’s see what they say official numbers.
Road safety data with the speed limit of 30 km/h
The ETSC report highlights how driving speed is a determining factor for severity of injuries in the event of an accident: the more the speed increases, the more the probability of serious trauma increases. Precisely for this reason, the Transport Safety Council has recommended that EU countries introduce the 30 km/h limit in residential areas and close to schools and playgrounds.
But, therefore, are there actually results in terms of road safety? According to a survey conducted by Ramboll, in the 40 European cities that have implemented 30 zones there was an average 23% reduction in accidents And of serious injuries by 38% . This is because the reduced speed of cars increases drivers’ reaction time and reduces the necessary braking distance, reducing the risk of high-impact collisions. the probability of avoiding collisions.
However, it is necessary to specify that this limit it does not eliminate the risks, especially for the elderly. As reported by the ETSC data, in the event of a collision with a vehicle traveling at a maximum speed of 30 km/h, a pedestrian of aged over 65 has the 15.4% probability of reporting serious injuries: under 65, the probability is 9.4%.
Data on traffic and pollution
From a traffic perspective, 30 km/h zones contribute to a significant reduction in traffic noiseuntil 3-5 decibels in urban areas, according to the average data recorded in the 40 European cities taken into consideration in the survey. Cities such as Brussels and Paris, in fact, have achieved noise reduction up to 50% on some secondary roads.
At the same time, the 30 km/h limit entails less sudden acceleration and brakingreducing tire and brake wear which, according to Ramboll’s study, can be responsible for over 75% of particulate emissions in urban contexts.
In short, by going slower, violent braking and sudden maneuvers are reduced and, consequently, PM10 concentrations may also drop, which is also affected by brake and tire wear.
The effect on emissions, however, strongly depends on driving style: since it is not certain that the 30 km/h limit is respected by all drivers, it is not certain that the impact on emissions is effective and tangible.
The 30 km/h limit alone is not enough
However, another interesting fact emerges from the ETSC report: the 30 km/h limit alone is not enough. The initiative, in fact, really works if supported by a strategy of “traffic calming“, with the aim of making compliance with this limit easier and discouraging higher speeds. All this translates into the introduction of barriers such as roundabouts, speed bumps or roadway narrowings, which actually physically slow down traffic.
To this must then be added gods effective controls – especially in the first period after the introduction of the 30 km/h limit –, which in turn can incentivize speed reduction if the previous measures are not sufficient.
In short, according to the European agency’s analysis, the 30 km/h limit in urban centers can only bring concrete results thanks to a combination between traffic calming measures (roundabouts, speed bumps, etc.) and road controls.
