The 35km Line 18 will run between Orly Airport and Versailles Chantiers and will have 21km of underground and 14km of elevated track. Egis will be responsible for managing all systems along the new route including stations, maintenance and operating sites. These systems include high and low voltage installations, platform screen doors, automatic train control systems, operating centres, tunnel ventilation and guidance.

The first section of Line 18 between Orly Airport and CEA Saint-Aubin is due to open in 2024 with the remaining section completed by 2030. A fleet of 30 45m-long automated trains powered by third-rail electrification will be ordered for Line 18 with headways of three minutes when the route is fully open.

The wider Grand Paris metro will see 200km of new tracks and 65 stations built to link suburbs in the French capital as well as more cross-city links. Egis was awarded a similar contract in 2014 for the infrastructure of Line 16, which runs from Noisy-Champs to Le Bourget RER station. It is also conducting a €25m study for the Le Bourget RER - Saint-Denis Pleyel - Saint-Ouen section, which will form Line 14 North and Line 17 South.