Diesel or electric: how modern trains get their power
Diesel-electric trains carry a power station on board; electric trains take power from a wire or rail, from 750 V DC up to 25 kV AC.
Why trains can't stop quickly: braking distance explained
Steel wheels on steel rail grip far less than rubber on road, so a train at 120 km/h needs about 800 m to stop where a car needs about 80 m.
Light rail and trams: how they differ from main-line trains
Trams drive on sight at about 750 V DC; UK main lines signal trains apart and use 25 kV AC. A typical tram stops in 39 m, a 100 mph train in about 2 km.
Level crossings: how automatic barriers know a train is coming
Track circuits, axle counters and treadles detect a train, and the strike-in point is set by distance = speed × warning time: 27 s at 100 mph is about 1.2 km.
Railway time: how trains standardised the clocks
Local noon moves 4 minutes per degree of longitude. See how that gap, about 10 minutes at Bristol, pushed railways to one standard time.
Tunnel or cutting: how engineers take a line through a hill
A cutting's volume grows with the square of its depth, a tunnel's only with its length. Work out where the break-even depth falls, with an example.
Coned wheels: how a train steers itself round a curve
A train has no steering wheel. Tapered wheel treads let the wheelset find the right path round a curve. See the geometry and a 500 m worked example.
Single track and passing loops: running trains both ways
One track, two directions. See how a section's running time caps the trains per hour, why one passing loop doubles it, and how tokens kept trains apart.
How a steam locomotive turns coal into motion
Coal heats water, the steam pushes pistons, and rods turn the wheels. Follow the chain link by link, and work out the pull of a typical two-cylinder engine.
Standard gauge: why most railways run on 1,435 mm
Standard gauge is 4 ft 8½ in, or 1,435 mm. It came from colliery wagonways, beat Brunel's 7 ft ¼ in broad gauge, and still shares the world with five others.
Railway towns: how a station made a village grow
Crewe, Swindon and Wolverton were hamlets or small market towns before the railway. What a station and a works did to them, with figures from the 1860s.
How railway bridges carry a load: four designs
Beam, arch, truss and suspension bridges all carry weight to the ground in different ways. Here is how each works and why heavy railways avoid suspension spans.
From coal mine to power station: how freight chains work
A 1 GW coal power station burns roughly 9,000 to 10,000 tonnes a day, about one unit train. The arithmetic, and why bulk freight suits rail.
How railway signals keep trains apart
Signals split the track into blocks so only one train occupies each. Braking distance grows with the square of speed, and that sets how far apart they sit.
Why railways follow rivers: gradients and the ruling grade
A steel wheel grips a steel rail with only a fraction of the train's weight, so every climb cuts the load an engine can pull. That is why early lines hugged river valleys.