A decision that does not meet with consensus. Starting Tuesday, October 1, Paris City Hall will lower the maximum speed on the Paris ring road from 70 to 50 km/h, three years after limiting the speed to 30 km/h within Paris itself. During the 2020 municipal election campaign, Anne Hidalgo and her running mate David Belliard (Les Ecologistes-EELV) had promised to transform the ring road into “a peaceful urban boulevard” limited to 50 km/h.
This 35 km municipal road, managed by the city of Paris, carries nearly 1.2 million trips per day, according to a study by the consulting firms Kisio and Roland Berger. Since the measure was announced, criticism has been rife. Former Transport Minister Clément Beaune had indicated at the end of 2023 that he would not validate it. “I think it’s not a good idea in the short term”he had advanced. For its part, the Ile-de-France region has expressed its desire to submit a motion on Wednesday, for “propose to the town hall to abandon this project”. Franceinfo studied the arguments for and against this measure.
“It will mainly affect non-Parisians”: true
The Paris city hall is accused of having taken a unilateral decision, penalizing non-Parisian users. The LR vice-president of the Ile-de-France region Othman Nasrou recalled on franceinfo that “80% of ring road users are people who do not live in Paris”. This measure “will once again penalize France on the other side of the ring road, which cannot do without its vehicle for its daily journeys“, Philippe Nozière, president of the association 40 million motorists, was indignant in a press release (PDF).
According to a regional survey on the mobility of Parisian residents by the Paris Region Institute, published in April, “80% of users of the ring road live outside Paris“: a figure which proves Othman Nasrou right. The study also reveals that 59% of trips are between Paris and the suburbs, and that 35% are from suburb to suburb. Only 6% are within Paris.
“It will reduce the noise”: rather true
This is one of the main arguments of the Paris city hall. Anne Hidalgo mentioned on Saturday August 31st to West France a “public health measure for the 500,000 people who live near the ring road”Speaking to franceinfo, David Belliard, deputy mayor of Paris in charge of the transformation of public spaces, transport, mobility, the highway code and roads, highlighted the results of a Canadian study published in The Lancetaccording to which living near major roads increases the risk of dementia, with pollution and noise as possible factors.
“Lowering the maximum speed represents a gain in terms of reduction of noise pollution (…) This is particularly true at night, because during the day, the average speed is less than 50 km/h”notes the ecologist elected official. According to Bruitparif (PDF), noise observatory in Ile-de-France, the lowering of the maximum speed of the ring road from 80 km/h to 70 km/h in 2014 has led to a reduction in noise of 1.2 decibels at night and 0.5 decibels during the day for local residents. A gain which is equivalent to a reduction in traffic volume of 25% and 10% respectively, according to the observatory.
However, according to a study by Ademe (the ecological transition agency) in 2014 (PDF), measuring the impact of speed limits on air quality, climate, energy and noise, it is indicated that “Speed limitation does not always lead to a reduction in noise levels.” The agency measured the effects of reducing speed on several types of roads, both express and urban. “All studies conclude that there is a generally low reduction in noise emissions with speeds”with a reduction of between 1 and 1.5 decibels on average for speed reductions between 50 and 90 km/h.
The study highlights that for low traffic speeds, other factors can generate noise: “development, road surfaces, high flow and nature of traffic”In other words, if reducing the maximum speed leads to a reduction in traffic congestion, coupled with good equipment, noise pollution will indeed decrease. “The coated [revêtement de la chaussée] of the ring road have not been redone for years, even though there are new materials that can reduce noise pollution. As for the projects [proposés par Les Républicains] “The city never followed up on the cover of the boulevard.” also tackled Valérie Pécresse, the president of the Ile-de-France region, on September 3 in The Parisian.
“There was no impact study”: true
In its press release, the association 40 million motorists insists on “the absence of studies on traffic transfer and impact on traffic”. An argument also taken up by the Republicans, Othman Nasrou denouncing on franceinfo a decision taken “alone against all”, “without impact study or consultation”. Pierre Chasserey, spokesperson for 40 million motorists, interviewed by franceinfo, also says “very interested in an impact study on traffic shift” that this measure would entail.
Indeed, the Paris city hall did not conduct an impact study prior to its measure. However, it is not required to do so.. Furthermore, legally, the municipality can decide alone on the maximum speed allowed on the ring road, but it will still have to count on the support of the State, which manages the automatic speed cameras. Valérie Pécresse had proposed in 2021 that the region take over management of the ring road, attracting the wrath of the city of Paris.
“It will congest traffic”: to be qualified
In The ParisianValérie Pécresse is already anticipating a disaster scenario. “Cars will be stuck on the boulevard [périphérique] and will go and take the small streets around”she believes. “When you lower the maximum speed, you reduce the accordion effects, that is to say acceleration and deceleration. De facto, you improve the fluidity of traffic”retorts David Belliard. In 2015, the Paris city hall and the police headquarters drew a positive assessment of the Paris ring road at 70 km/h, with a “improvement of average traffic speeds” by 18% during peak hours in the morning and 12% in the evening.
“The speed made more regular (…) facilitates the insertion of vehicles onto the ring road”, explained the Parisian municipality and police. A gain was also noted in the duration of journeys. The 2014 Ademe study goes in the same direction: “The change from 80 to 70 km/h on a congested road generally improves traffic flow”. But what about a change from 70 km/h to 50 km/h? This configuration is not studied by the ecological transition agency.
“It will reduce pollution”: to be qualified
Does driving slower mean polluting less? In its 2026-2030 Climate Plan, the city of Paris anticipates “a reduction in air pollution” thanks to its measure.”It is generally considered that reducing speed reduces fuel consumption and unit pollutant emissions”, confirms Ademe in its study, while nevertheless suggesting a relationship “complex” between speed and air pollution. “It is road traffic that is responsible for the excess pollution. But the primary factor is not speed,” explains to franceinfo Pierre Pernot, engineer at Airparif, an organization that measures air quality in France.
“To act on this traffic, the strongest influencing factors are the number of vehicles passing, the type of vehicle, and the presence of congestion”he explains. “The reduction alone of the limit to 50 km/h instead of 70 will have a very limited impact on air pollution”except for the oldest vehicles, says Catherine Léger, director of Airparif with West FranceIn Paris, no study has assessed the impact on air quality of the move to 70 km/h on the Paris ring road.
“Above 70 km/h, speed reductions have a rather positive effect on particulate and nitrogen oxide emissions. Below 70 km/h, this effect is rather negative.“, even notes the 2014 study by Ademe. On urban roads (50 km/h to 30 km/h), Ademe notes contrasting developments, ranging from “-40% to +30% for NO2 concentrations [dioxyde d’azote]from -45% to +100% for benzene concentrations”. Again, it all depends on traffic.
In 2015, Rennes city hall and the prefecture experimented with a speed reduction of 20 km/h on different parts of the Rennes ring road. The results are also mixed: while the metropolis observes a “sharp drop in pollution“Thanks to the reduction from 110 to 90 km/h on the eastern and northern ring roads, this is not the case with the reduction from 90 to 70 km/h on the southern and western ring roads,” reports The Dispatch. It was therefore decided to harmonize the entire ring road to 90 km/h.
“It will reduce the number of accidents”: rather true
David Belliard spoke to franceinfo about a desire to improve the “road safety” thanks to their measurement. “We want to consider the ring road as a classic route”he justified. With the 70 km/h ring road, the number of accidents decreased by 15.5% (627 compared to 742) in 2014 compared to 2013, according to the report from the Paris city hall and the police headquarters. But the more recent reports seem more contrasted, according to figures obtained by the specialist site Caradisiac : between 2013 and 2018, the number of accidents only fell by 7.82% (684 compared to 742) and the number of deaths remained the same (4).
“In the event of an accident, the mortality rate is all the greater the higher the speed and the more less protected”however, recalls the Center for Studies and Expertise on Risks, the Environment, Mobility and Planning (Cerema) in a 2006 note (PDF). “If we assign the value 1 to a shock at 50 km/h, it will be 2 at 70 km/h”the note specifies. In other words, by going from 70 km/h to 50 km/h, the violence of the impact will be halved.
Cerema cites the example of two countries where lowering the speed limit from 60 to 50 km/h in built-up areas had a positive impact: Switzerland and Denmark, which reduced the number of accidents by 9% in 1982 and 1985 respectively. Furthermore, “A 1% drop in average speed mechanically reduces the fatal accident rate by 4%“, according to the Road Safety website. According to this, speed is the leading cause of road deaths in France, being responsible for 31% of accidents.