Heatwave in Île-de-France: why is transport traffic disrupted?

How does the heat impact your public transport?

#1. Live electrical cables = train slowdowns with the heat

Overhead electrical cables (called catenaries), which power a large part of the trains, trams and RER, are affected by the heatwave.

With the heat, they can relax or break, causing power cuts and unplanned traffic stops during heat waves.

#2. High heat means the risk of rail expansion

It is a natural phenomenon, when temperatures exceed 30 °C, the metal of the rails heats up and expands, reaching between 50 and 60 °C (when the outside temperature exceeds 37 °C).

This expansion can cause a slight deformation of the tracks, which can become dangerous if trains are travelling at normal speed. In places, the rails are painted white to reduce their temperature and limit expansion.

What measures are taken on traffic to guarantee your safety in the event of a heat wave?

Since 2016, all vehicles purchased or renovated have been systematically equipped with air conditioning or refrigerated ventilation to adapt to summer temperatures.

Since then, a total of 1,600 new or renovated trains, RER and metros have arrived on your lines.

Enhanced monitoring of infrastructure and rolling stock

The technical teams that manage the day-to-day operation of the lines (SNCF Réseau and RATP) are mobilised to inspect the tracks and monitor trains, trams and RER trains in real time.

High temperatures = immediate adaptation of traffic

When temperatures exceed the 30 degree threshold:

• Speed limits are in place
• Trains can be cancelled or their circulation reorganised (when the rails have become too deformed)to maintain an optimal level of safety for passengers

Objective? Air conditioning for your journeys

To improve the comfort of your journeys, Île-de-France Mobilités is investing in equipping all its vehicles with refrigerated ventilation or air conditioning.

In June 2026:

• Tramway: 100%of trams are air-conditioned in Île-de-France
• Trains and RER: 75% of trains are equipped with refrigerated ventilation or air conditioning, i.e. 3 out of 4
• Buses and coaches: 60% of the fleet is air-conditioned, including 100% of coaches and 50% of buses
• Metro: 50% of metros are equipped with refrigerated ventilation, i.e. 1 in 2. Almost the entire metro network will be air-conditioned by 2033, with the arrival of the MF19

Note : Lines 1, 2, 5, 9, 11 and 14 are 100% equipped with refrigerated ventilation.

On your side: what to do in the event of a heat wave?

• Before leaving home, regularly check the traffic information to anticipate your journeys : on the Île-de-France Mobilités app, on your usual transport app or on the screens in stations and stations
• If possible, adapt your departure time as much as possible by avoiding peak hours (7:30 a.m. / 9:30 a.m. and 4:30 p.m. / 7:30 p.m.), in order to travel more serenely
• Hydrate yourself well during your journeys and bring your water bottle, drinking water fountains are available everywhere in the Region and in more than 131 stations and stations in Île-de-France
• Adapt your journey to take air-conditioned lines: on the Île-de-France Mobilités app, air-conditioned lines are indicated to passengers when searching for directions
• Stay in the shade: for each trip, bring a hat or umbrella to avoid strong exposure to the sun. The Île-de-France Region lists, on its website, the climate shelter areas in the vicinity