OpenTTD (2004)

Signals, station approaches and vehicle routes make a busy railway something you can diagnose and redesign rather than merely watch. Cargo and passengers create reasons to connect places, with running costs giving unused capacity a price. Choose it for a deep transport sandbox that remains free from the project's website. New Steam or GOG access now comes through a paid Transport Tycoon Deluxe bundle. The older interface and signalling rules need learning, but a useful junction can reward that effort for years of simulated traffic.