The fourth era features 3 passenger trains named after ancient gods and heroes, with one being a bonus engine.
You can unlock engines by spending research points generated by the Laboratory in your Train Station. Once the required pre-requisites are met, you can develop the next engine. At the end of each era, a coupling system becomes available, allowing engines to transport goods from the next era.
Note: You don’t need to research anything from previous eras to begin researching Era 4 engines.
Hermes
Requirements:
Research the Apollo cargo engine
Research Tractive Force I+II and Reliability upgrades
Research Cost: 50 Research Points
Slots: 1 | Reliability: 80% | Acceleration: 16/20 | Speed: 280 km/h | Passengers: 65
Hypnos
Requirements:
Research the Horus or the Neptune and required upgrades
Research Cost: 60 Research Points
Note: Hypnos is a multi-slot engine and takes up 3 slots instead of 1.
Slots: 3 | Reliability: 50% | Acceleration: 2/20 | Speed: 90 km/h | Passengers: 390
Hades (Bonus)
The Hades is the Passenger Bonus Engine of Era 4.
It can be bought in the Rail Nation Shop or won through the Lottery or competitions in Era 5.
Note: The cost decreases if purchased in a later era.
Slots: 0 | Reliability: 90% | Acceleration: 10/20 | Speed: 230 km/h | Passengers: 110