Climate solutions tailored to our different transport modes

RATP is working closely with Île-de-France Mobilités, which funds the renewal of rolling stock, to better address the impact of extreme heat on the network.

The transition to more air-conditioned and air-cooled rolling stock

Our main area of action lies in modernising our fleet, given that several generations of rolling stock currently coexist across the network as part of a gradual renewal programme. The newest vehicles are equipped with either an air-cooling ventilation system or low-energy air conditioning. Older rolling stock, however—particularly trains—was not originally designed with today's climate-related challenges sufficiently in mind.

• Air-cooling ventilation system: this system lowers the temperature of the air inside train carriages by a few degrees compared with the outside air, providing passengers with a feeling of freshness and improved comfort while using less energy than conventional air conditioning.
• Air conditioning: this system regulates the indoor air temperature around a predefined set point, regardless of the temperature outside.

Current fleet data is set out below.

Metro

50% of the fleet is equipped with an air-cooling ventilation system (lines ), as well as part of the fleet operating on metro line (31 trains). In addition, trains on line are being modernised through the gradual introduction of the MF19 (currently 4 trains are in service).

The remainder of the fleet relies on natural or forced ventilation using fans to create air movement. These systems, fitted to older metro trains, are no longer considered adequate in view of the increasing frequency of heatwaves.

All future rolling stock (MF19), which will be rolled out across the network between 2025 and 2034, will be equipped with an air-cooling ventilation system.

RER

93% of the fleet is equipped with air-cooling ventilation systems.

• On line, the MI09 and MI2N trains are fitted with an air-cooling ventilation system.
• On line, all refurbished MI79 and MI84 trains (representing 84% of the fleet) are equipped with an air-cooling ventilation system.
• The future MI20 rolling stock, which will be introduced on line B, will also be fitted with an air-cooling ventilation system.

Tram

All tram lines operated by RATP on behalf of Île-de-France Mobilités () are equipped with an air-cooling ventilation system.

Bus

The rollout of air conditioning across the bus fleet has accelerated significantly in recent years, driven by Île-de-France Mobilités through the gradual renewal and decarbonisation of the RATP fleet as part of the (Bus 2025 programme). For example :

• In 2020, 5% of RATP buses were equipped with an air-cooling ventilation system.
• In 2022, 24% of RATP buses were equipped with an air-cooling ventilation system.
• In 2023, 32% of RATP buses were equipped with an air-cooling ventilation system.
• In 2024, 40% of RATP buses were equipped with an air-cooling ventilation system.
• In 2025, 49% of RATP buses were equipped with an air-cooling ventilation system.
• By 2035, 100% of the fleet currently operated by RATP on behalf of Île-de-France Mobilités is expected to be equipped with an air-cooling ventilation system.

Every summer, nearly 100 additional staff members (known as the “Green Vests”) are recruited and trained to strengthen our on-the-ground teams and provide assistance and guidance to passengers.

During periods of extreme heat, our staff help raise awareness of essential heatwave safety advice and prevention measures. In partnership with Santé Publique France, prevention posters are also displayed throughout metro and rail stations.

In addition, when passengers need to be assisted during the evacuation of a train in a tunnel, bottled water is delivered and distributed as part of the response arrangements.

Expanding the network of drinking water fountains

During a heatwave, staying hydrated is essential. To support this, RATP is gradually installing drinking water fountains across its network. More than 100 drinking water fountains are already available across the Île-de-France Mobilités network operated by RATP, including at stations such as Auber, Nation, and Châtelet. In addition, a partnership with Eaux de Paris enables passengers to locate the nearest drinking water fountains to metro and RER stations via the RATP website.

Bus drivers, who are particularly exposed due to their glass-fronted driving cabins, benefit from dedicated measures as soon as periods of extreme heat begin. These measures include:

• permission to wear zip-off trousers, or, for female drivers, a wrap skirt, in addition to the standard uniform;
• the provision of chilled bottled water and drinking fountains at termini to facilitate hydration;
• cooling towels made available at bus depots;
• adjustments to layover times to allow drivers to cool down;
• extended break periods during heatwaves.

Similar measures are implemented for train drivers and station staff across the rail network.

Driving cabs, not all of which are equipped with air conditioning, are subject to monitoring. Once certain temperature thresholds are reached (between 25°C and 30°C), heat checks are carried out. These assessments may result in extended break periods for drivers or, where necessary, a reduction in the number of services they operate.

For station and transport hub staff, an extended-break system is also in place, alongside the distribution of drinking water and access to hydration points. Air-conditioning and cooling systems in staff facilities are regularly inspected and maintained to ensure they operate effectively.
In addition, RATP is currently trialling different types of cooling vests with approximately ten RER employees, as well as cooling insoles, particularly for staff who work on ballasted track, which can become extremely hot during the summer months.

Infrastructure monitoring

Heat is not only a passenger comfort issue; it is also an infrastructure challenge. Periods of extreme heat can affect infrastructure and cause damage that may impact services, such as deterioration of certain cables or the shutdown of equipment when temperature thresholds are exceeded.

To reduce the risk of incidents linked to these extreme operating conditions, monitoring and preventive maintenance measures have been strengthened over recent years to improve the resilience of our infrastructure during hot weather. These measures include:

• continuous monitoring of infrastructure and, where necessary, the introduction of speed restrictions once rail temperatures reach 57°C;
• dedicated “heat inspections” carried out to monitor tracks and detect any anomalies that could affect train operations or railway safety. As rails are particularly sensitive to temperature fluctuations, rail temperature readings are taken daily between 15 May and 15 September.
• regular inspections of signalling facilities known to be particularly exposed to high temperatures;
• comprehensive preventive maintenance of UPS systems and other sensitive equipment in Operations Control Centres (OCCs) ahead of the summer season.

Routine inspection programmes for overhead line equipment are also reinforced. In addition, over the past four years, RATP has deployed around twenty connected sensors to provide real-time rail temperature data across above-ground sections of the network. Installed on metro, tram, and RER lines operated by RATP on behalf of Île-de-France Mobilités, these sensors are linked to a predictive model capable of anticipating changes in the internal temperature of the rail.

Particular attention is also paid to overhead catenary systems as part of seasonal monitoring activities, with enhanced surveillance during periods of extreme heat. Where necessary, RATP may decide to temporarily reduce train speeds or lower pantographs in particularly sensitive areas.

Rolling stock monitoring

Preventive maintenance operations are carried out regularly on rolling stock to minimise the risk of ventilation system failures during hot weather. 

• For rail vehicles, this includes replacing filters, cleaning evaporators and condensers, checking cooling circuits, and cleaning water drainage systems.  
• For buses, maintenance includes inspections of air-conditioning units and ventilation systems, filter replacement, and cleaning cooling radiators.