Compare the main types of train engines and traction—steam, diesel, electric, battery, hybrid and dual-mode—and learn how each works.
The main types of train traction are steam, diesel and electric. Diesel traction divides into diesel-mechanical, diesel-hydraulic and diesel-electric systems, while electric trains collect power from overhead wires or a third rail. Battery, hybrid, hydrogen fuel-cell and dual-mode trains extend those categories. Multiple units describe train formation, not a separate power source.
What does “train engine” mean?
A locomotive is a powered railway vehicle built primarily to haul a train, while an engine is technically the machine producing mechanical power. An electric locomotive has traction motors but no conventional engine, so railway simulators and operators usually use traction type as the broader term.
Traction type should not be confused with tractive effort. Tractive effort is the pulling force available at the wheels; it varies with speed, adhesion, gearing and locomotive power.
The main railway traction types compared
Most simulated trains fit into one of the following traction systems, although individual locomotives can combine more than one.
| Traction type | How it drives the wheels | Typical simulator controls |
|---|---|---|
| Steam | Fuel heats boiler water; expanding steam drives pistons connected to the wheels. | Regulator, reverser, dampers, blower, injectors and firing controls. |
| Diesel-mechanical | A diesel engine drives the axles through a clutch and mechanical gearbox. | Throttle, gears, clutch or an automatic transmission selector. |
| Diesel-hydraulic | A diesel engine transfers power through a fluid coupling or torque converter. | Reverser, power controller and brakes; transmission changes may be automatic. |
| Diesel-electric | A diesel engine turns a generator or alternator, which supplies electric traction motors. | Engine start, reverser, power notches, generator field and often dynamic braking. |
| Electric | Overhead wires or a third rail supply electricity to traction motors through control equipment. | Pantograph or shoe equipment, main circuit breaker, master controller and regenerative braking. |
| Battery or fuel-cell electric | Batteries supply the motors directly, or a hydrogen fuel cell generates electricity onboard. | Master controller, battery state or energy display and regenerative braking. |
| Hybrid or dual-mode | Two power sources are combined or selected, such as overhead electricity and a diesel engine. | Power-mode selection, source-change procedures and the controls required by each mode. |
For practical examples of how the three traditional groups differ in the cab, our guide to diesel, electric and steam controls in Train Simulator Classic covers the basic operating sequence.
Is a diesel-electric locomotive diesel or electric?
A diesel-electric locomotive is classified as diesel traction because its primary power source is an onboard diesel engine. The electrical equipment is its transmission: the engine drives a generator or alternator, and electric motors turn the axles.
This arrangement avoids a large mechanical gearbox and provides strong low-speed control. In a simulator, an idling engine does not necessarily mean traction is ready; the generator field, direction selector, isolation controls and brake interlocks may still prevent power from reaching the motors.
Are DMUs and EMUs separate traction types?
DMU and EMU describe how powered vehicles are arranged within a train, rather than introducing new energy sources.
- DMU: a diesel multiple unit, which may use mechanical, hydraulic or electric transmission.
- EMU: an electric multiple unit supplied by overhead wires or a third rail.
- BMU: a battery multiple unit using stored electrical energy.
- Bi-mode multiple unit: a train able to change between two sources, commonly external electricity and onboard diesel power.
A locomotive concentrates traction equipment in one vehicle and hauls unpowered coaches or wagons. A multiple unit distributes powered axles and equipment through the train.
How do traction types feel in a train simulator?
Each traction type changes the workload, power response and mistakes that can stop a simulated train.
- Steam demands the most continuous management. Boiler pressure, water level, fire condition, regulator and reverser settings interact, so opening the regulator fully is rarely the complete answer. The full steam-locomotive control sequence in Train Sim World explains these dependencies.
- Diesel-mechanical and diesel-hydraulic traction can require gear or transmission management. Poor gear selection may cause weak acceleration or engine overspeed.
- Diesel-electric traction usually uses power notches and may provide dynamic braking. Too much power at low speed can cause wheel slip, especially with a heavy consist.
- Electric traction often delivers strong starting effort, but the pantograph or collector, main circuit breaker and correct electrical system must be available. A lit cab can be running from its low-voltage battery while the traction supply remains disconnected.
- Battery, hybrid and dual-mode trains add energy limits and source-change procedures where the add-on models them.
A mistake we see constantly is treating the power handle as a direct speed control. It commands traction effort or power; acceleration still depends on train mass, gradient, adhesion and resistance. Our heavy-freight starting and braking techniques show why gradual power application matters.
Does traction type determine the braking system?
Traction type influences the available locomotive brake, but it does not by itself determine the train’s complete braking system. Steam, diesel and electric locomotives can haul vehicles using compatible air or vacuum brakes, depending on the railway and period.
Diesel-electric and electric trains may also use dynamic or regenerative braking. These systems slow the powered axles but may blend with friction brakes, weaken at low speed or be unavailable when the electrical system cannot accept the generated energy. Always check what the specific simulated vehicle models.
Why does a locomotive have power but not move?
A powered cab is not proof that traction is available; an open circuit breaker, neutral reverser, applied brake or safety interlock can still block movement.
- Enable the driving cab. Insert or activate the master key and select the intended direction.
- Establish the power source. Start the diesel engine and enable its traction equipment, or raise the correct pantograph and close the main circuit breaker.
- Prepare the brakes. Allow the brake system to charge, then release the train, locomotive and parking brakes as applicable. Air and vacuum gauges use different conventions, so do not assume a higher reading always means the same thing.
- Clear the interlocks. Close the doors, acknowledge active safety systems and return the power handle to its required reset position after an emergency or wheel-slip event.
- Apply a low power setting. Watch the ammeter, tractive-effort display or engine response rather than immediately selecting maximum power.
- Check the consist. A handbrake, incompatible brake setup or incorrectly configured trailing locomotive can hold the entire train.
For a more detailed fault sequence, use our Train Sim World traction and brake diagnostic checklist.
Which traction type is best for a beginner?
A straightforward diesel-electric locomotive or modern multiple unit is usually the easiest starting point because basic power and brake control can be learned without managing a steam boiler or manual gearbox.
Choose a vehicle supplied with the route so its electrification, signalling and operating instructions match. Pick steam when you want hands-on systems management, diesel for broad route flexibility, and electric traction for rapid response and power-supply procedures. The complexity of the individual add-on matters more than the traction label alone.