The Brussels S Train, also known as the Brussels Regional Express Network (French: Réseau Express Régional Bruxellois or RER; Dutch: Gewestelijk ExpresNet or GEN) is a suburban rail system in and around the Brussels-Capital Region of Belgium. It will offer fast connections and increased frequency within a 30 km (19 mi) radius of the region, covering a territory inhabited by 2.5 million people.
Most jobs in the Brussels-Capital Region are filled by workers from other regions. Private vehicles clog the city daily, hampering mobility and creating pollution. The RER/GEN is a response to these growing problems. Only 20% of commuters use public transport daily; the goal is to double this figure by facilitating movement into and within the region.