In 2020, SNCF launched PLANETER, a program to reduce the environmental impact of regional mobility based on the belief that with more regional trains, there will be much less GHG. To further reduce CO2 emissions, in addition to the work concerning operation topics (optimal driving, eco-stationing, regularity,…), SNCF investigate several solutions for greening its fleet: biofuel, hybrid trains, hydrogen trains, and battery trains.